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Availbale Products, Material- and Service suppliers => Do It Yourself => Topic started by: MarkE on February 14, 2015, 10:35:20 PM
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This thread is to discuss oscilloscopes and good measurement practices using oscilloscopes.
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Good topic Mark. This will help me a lot I am sure, as well as many others.
Bill
PS http://www.ebay.com/itm/New-Function-signal-generator-source-frequency-signal-generator-finished-board/131063212194?_trksid=p2054897.c100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140407115239%26meid%3 (http://www.ebay.com/itm/New-Function-signal-generator-source-frequency-signal-generator-finished-board/131063212194?_trksid=p2054897.c100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140407115239%26meid%3Ddee726ea5268418aaae964634ecd71a2%26pid%3D100204%26rk%3D7%26rkt%3D28%26mehot%3Dpp%26sd%3D361077176699)
Ddee726ea5268418aaae964634ecd71a2%26pid%3D100204%26rk%3D7%26rkt%3D28%26mehot%3Dpp%26sd%3D361077176699 (http://www.ebay.com/itm/New-Function-signal-generator-source-frequency-signal-generator-finished-board/131063212194?_trksid=p2054897.c100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140407115239%26meid%3Ddee726ea5268418aaae964634ecd71a2%26pid%3D100204%26rk%3D7%26rkt%3D28%26mehot%3Dpp%26sd%3D361077176699)
Is this FG worth getting if you don't have any as of yet? (In other words, better than nothing?)
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Now we need some tutor :D
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The basics of your average passive oscilloscope probe:
Most passive probes come in x1/x10 switchable configurations. The oscilloscope itself contains the amplifiers which have a 1 megOhm resistance from the channel input to ground. When set for x1, the probe is basically a coaxial cable connection from the probe to the oscilloscope. The coaxial cable for a typical 1.5 meter scope cable has a total of about 50 - 100pF capacitance. That is a parasitic that the circuit under test has to drive.
When the probe is in the x10 mode a 9Meg Ohm resistor gets switched in at the probe. That's the good news. The bad news is that 9Meg Ohms forms a low pass filter with the cable capacitance that kills the frequency response. In order to restore the response: the probe includes a small capacitance of 10 - 20pF in parallel with the 9 Meg Ohm resistor. The circuit being measured now drives 10-20pF in parallel with 9Meg Ohms instead of driving 50 - 100pF in parallel with 1 Meg. 10-20pF may not seem like a lot, but that depends on how fast the signal is. At 1MHz 16pF is ~10K Ohms, a far cry from the total 10M Ohms of the probe at DC.
The next problem is signal reflections. Anytime a signal travels through a transmission like, such as the coaxial cable of an oscilloscope probe, whereever the impedance changes there is a reflection: A ghost signal that travels in all directions from the point where the impedance changes. When the cable is electrically short compared to the frequency content of the reflection, the reflection is not noticeable. Where the cable is longer than about 1/10th the rise time of the signal, or about 1/3 the frequency of a sine wave, the reflections become a big issue. Remember that the oscilloscope input is 1 MegOhm. A typical coax probe cable has a transmission line impedance near 100 Ohms. This is a very bad mismatch. Without adjustment, the signal that hits the amplifier nearly doubles due to the reflection. In order to get around that, the probe has a series resistor past the 10-20pF compensation capacitor that matches the transmission line (coax cable) impedance to try and cut the signal by half so that when the signal doubles at the scope input the result is correct when it first hits. The ghost signal still needs to be absorbed by the time it gets back to the probe. The series resistor would do that if the DUT circuit had zero impedance. That means the DUT circuit sees that reflected ghost energy. But it sees it through the probe. When the probe is connected using a 4" or 6" ground clip, that introduces inductance that resists passing the fast changing waveform of the ghost reflection. As a result, the ghost reflection is not completely absorbed and now what remains of it goes zooming back down the cable towards the oscilloscope where it will be seen as signal.
These reflections that are made much worse by the ground clip generates ringing that may not settle for 50ns or longer. This makes it hard to measure narrow spikes accurately, especially using the oscilloscope probe ground clip, and where the circuit under test has a high impedance. There are vaious techniques to mitigate these problems.
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Good topic Mark. This will help me a lot I am sure, as well as many others.
Bill
PS http://www.ebay.com/itm/New-Function-signal-generator-source-frequency-signal-generator-finished-board/131063212194?_trksid=p2054897.c100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140407115239%26meid%3Ddee726ea5268418aaae964634ecd71a2%26pid%3D100204%26rk%3D7%26rkt%3D28%26mehot%3Dpp%26sd%3D361077176699 (http://www.ebay.com/itm/New-Function-signal-generator-source-frequency-signal-generator-finished-board/131063212194?_trksid=p2054897.c100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140407115239%26meid%3Ddee726ea5268418aaae964634ecd71a2%26pid%3D100204%26rk%3D7%26rkt%3D28%26mehot%3Dpp%26sd%3D361077176699)
Well it's better than nothing. What works pretty well are the 3D25 USB generators from Hantek. They go for about $160. and produce decent signals from 1Hz to ~10MHz ( they say 20MHz ) and are easy to control. The signal output is limited to +/-3V into 50 Ohms which is so-so. but one can add a voltage amplifier behind them if one is so inclined. The next step up is to purchase a standaolne FG. New, a decent digial one starts at about $350.
Is this FG worth getting if you don't have any as of yet? (In other words, better than nothing?)
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Thanks Mark.
Hey, if you repost your above response and requote my post, it is now sized to fit the page. I have no idea why the link I posted ran off to the
right so far. I split it up so now it fits the page. If you re-do your quote of my post, it will now fit.
Sorry.
Bill
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@MarkE: Thank you for starting this topic. I hope to learn a lot from it, and may be able to contribute a thing or two myself.
@Pirate: If you're a fan of classic analog equipment...
http://www.ebay.com/itm/Interstate-Electronics-Corporation-F-34-Function-Generator-115v-230v-/271740054768
;)
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@Pirate: If you're a fan of classic analog equipment...
http://www.ebay.com/itm/Interstate-Electronics-Corporation-F-34-Function-Generator-115v-230v-/271740054768
;)
OOOOhhhhH...... I just might have to snatch that one out from under ya!!! haha just playin, just playin... it's all yours...
unless I get it first!! AHHHH
kidding. I do need a FG though. not yet though, already have enough to learn and a PC/amp will be OK for the time being, esp since I can shut off my DC offset and disable all enhancements.
I'm going to bring my reply regarding the scope and arduino over to this thread.
@Brian, yes, I think it would be a good value especially if you don't want or need the stuff you are trading for it. You are right that it may just need cleaning of the switch contacts. If it needs repair that too can be managed; as you found out there are replacement boards available for the vertical amplifiers and even if you had to replace the entire VA board rather than just a component you will still be way ahead. I haven't looked at a 465 Service Manual but the Tek manuals generally are very complete and will have troubleshooting and calibration guides along with complete schematics so tracking down the problem may be fairly straightforward.
I've seen a few scopes that were advertised as "not working" and it turned out that the sellers just didn't know how to get a trace to show up! Probably not that simple in your case though but one could always hope.
Arduinos are a _lot_ of fun and I'm always amazed at what can be done with them. And the programming language is essentially c++, which is great!
Wish me luck tomorrow with this O-scope! Let's hope the repairs will just be a nice, thorough cleaning which I will be giving it regardless! If not, I'll go thru and test all the caps, resistors, transistors etc etc if I must, and worst case I'll just buy a new VA board. I'm quite anxious, though.... I've never even touched a scope, so I've been watching vids non-stop about how to use it so I don't screw anything up before I even bring it home! I'm going to have him start it up and do the first test run off my PC FG, just in case he's some nut con man trying to pull a fast one and toss off a broken piece of equipment on me! Gotta be uber careful with craigslist people.. you just never know...
As for the PC FG, I just wanna mention for the benefit of all, Visual Analyzer is pretty good software. if you haven't heard of it, you should def check it out!
I found the factory service manual for it and scanned thru it, it definitely seems quite thorough. It's got schematics, troubleshooting, and quite a bit more, so definitely good to have! I wish I could run across some of those people that have stuff I need and haven't a clue and don't care to! Maybe I'll luck out this spring at some yard sales.... $5 FG WHAAAAATT?? (that would be awesome!)
I have some books on C++ somewhere. Never did get around to learning it, though. I guess I have some motivation now. What add-on board do you think I should get first, besides an LCD or a touch screen?
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OOOOhhhhH...... I just might have to snatch that one out from under ya!!! haha just playin, just playin... it's all yours...
unless I get it first!! AHHHH
kidding. I do need a FG though. not yet though, already have enough to learn and a PC/amp will be OK for the time being, esp since I can shut off my DC offset and disable all enhancements.
I'm going to bring my reply regarding the scope and arduino over to this thread.
Wish me luck tomorrow with this O-scope! Let's hope the repairs will just be a nice, thorough cleaning which I will be giving it regardless! If not, I'll go thru and test all the caps, resistors, transistors etc etc if I must, and worst case I'll just buy a new VA board. I'm quite anxious, though.... I've never even touched a scope, so I've been watching vids non-stop about how to use it so I don't screw anything up before I even bring it home! I'm going to have him start it up and do the first test run off my PC FG, just in case he's some nut con man trying to pull a fast one and toss off a broken piece of equipment on me! Gotta be uber careful with craigslist people.. you just never know...
As for the PC FG, I just wanna mention for the benefit of all, Visual Analyzer is pretty good software. if you haven't heard of it, you should def check it out
I found the factory service manual for it and scanned thru it, it definitely seems quite thorough. It's got schematics, troubleshooting, and quite a bit more, so definitely good to have! I wish I could run across some of those people that have stuff I need and haven't a clue and don't care to! Maybe I'll luck out this spring at some yard sales.... $5 FG WHAAAAATT?? (that would be awesome!)
I have some books on C++ somewhere. Never did get around to learning it, though. I guess I have some motivation now. What add-on board do you think I should get first, besides an LCD or a touch screen?
eBay has some function generators for $60 - $80 that do two channels to 2MHz or 5MHz and 20Vpp open circuit w/ 50 Ohms impedance. That would cover a lot of needs.
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once I unload this mountain of stuff I have to sell on ebay, I'll grab up some more equipment. all my funds lately have been going towards getting caught up. sucks, but worth it.
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@MarkE: Thank you for starting this topic. I hope to learn a lot from it, and may be able to contribute a thing or two myself.
@Pirate: If you're a fan of classic analog equipment...
http://www.ebay.com/itm/Interstate-Electronics-Corporation-F-34-Function-Generator-115v-230v-/271740054768 (http://www.ebay.com/itm/Interstate-Electronics-Corporation-F-34-Function-Generator-115v-230v-/271740054768)
;)
That looks cool....thanks. I love classic equipment.
Bill
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I have some books on C++ somewhere. Never did get around to learning it, though. I guess I have some motivation now. What add-on board do you think I should get first, besides an LCD or a touch screen?
Depends on what you intend to do. There are literally hundreds of "shields" out there. The first "shield" that I got was the RuggedCircuits "Gadget Shield" just to play around with; it has 3-axis accelerometer, IR detector, IR emitter, RGB high-brightness LED, 2 potentiometers, 2 pushbuttons, 4 LED's, visible light sensor. The demo sketch for this one does things like have the RGB LED driven by the accelerometer, so it changes color as you tilt the thing around, etc. I also have their "Aussie shield" which is just a "breakout" board with easy quick-connectors for external wiring. For the LCD, I have a Parallax branded thing that has a backlight and a little piezo speaker, that is part of the Parallax Propeller system, it uses just a single data line (serial interface) and the two power leads so you don't tie up lots of the Arduino output pins driving a raw LCD. I also have another LCD shield that has buttons but it uses the regular interface so it uses up 7 outputs IIRC. I don't have any experience with touchscreens so I can't recommend one. I've got a motor driver shield with high-output H-bridge motor driver chips on it for robotics stuff, rc servos and steppermotors. Also a prototype shield that has pads to build your own circuits on, I put a high power mosfet switch circuit on this one.
There are even signal generator shields and video displays that you can get for the silly things, probably even full oscilloscope shields.
http://playground.arduino.cc/Main/SimilarBoards (lists many hardware items, shields etc with functional descriptions)
http://shieldlist.org/ (http://shieldlist.org/) (listed by manufacturer not type, unfortunately)
If you already have some programming experience but just not with c, or even if you don't, probably the best way to learn is just to look at example sketches and start changing them and see what happens. It's really pretty easy to do the basic stuff, the Arduino IDE comes with a lot of basic example sketches. Most people start with the "blink" sketch which just blinks an LED. The Arduino online references are excellent and the programming interface is portable, runs on any computer OS, so you can write your sketches on a Mac, load them with Linux, run and display serial data on Windoze etc.
Here's a handy thing I made:
http://www.youtube.com/watch?v=S6N8ys8FiA4
And just to steer back to the topic of oscilloscopes, here's a scoposcopy video showing how the Inductometer does its magic:
http://www.youtube.com/watch?v=Qx3B89379eQ
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That looks cool....thanks. I love classic equipment.
Bill
It's kind of limited in that it only goes to 3MHz and has a low output level, but it's very versatile in its trigger/gating functions and it has the external VCO input so you can control it from an external variable voltage source. I have one of these in storage in Canada that I paid a lot more money for than the selling price here. My regular workhorse is another Interstate FG, the F43 model "High Voltage" FG, it doesn't do sweep but it has 40 v p-p into 50 Ohms output.
It is handy to have a higher voltage output level as well as a higher frequency range, so the more modern ones MarkE found on EBay are worth a look too.
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My question is than what setup (1x,10x...) to use when. Currently I have my probes permanently set to 10x. Any general rule?
Next question - would it make sense to use de-coupling 1pf capacitor - sometimes I do use 1pF 5% 1KV - but to be honest I do not see much difference on the screen when using it.
I am planning to buy 100x probe. - yes/no? suggestions?
TK, you was talking about integration MATH function, what is that good for?
50Hz modulation from the main- is it big issue? any chance to filter it out?
Thanks.
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My question is than what setup (1x,10x...) to use when. Currently I have my probes permanently set to 10x. Any general rule?
Next question - would it make sense to use de-coupling 1pf capacitor - sometimes I do use 1pF 5% 1KV - but to be honest I do not see much difference on the screen when using it.
I am planning to buy 100x probe. - yes/no? suggestions?
TK, you was talking about integration MATH function, what is that good for?
50Hz modulation from the main- is it big issue? any chance to filter it out?
Thanks.
Use 10X almost exclusively. The only time 1X is useful is for low-level signals. 10X always offers equal or better fidelity and less loading on the circuit being tested.
Filters can be useful, there are several ways to go about them. Most scopes have a 20MHz bandwidht limiting option on the front panel. From a noise standpoint they are best to put at the scope input. Inserting 1.5K Ohms in series with 100pF to ground gives a decent performing 1MHz cut-off with low DC error. You can solder the parts between a male and female BNC connector, and then hot glue over it.
Integration of instantaneous power yields energy, and energy divided by time gives average power over the time interval used, such as one cycle of a periodic waveform.
If you are picking up 50Hz, then:
1) Your signals are very small and high impedance. OR
2) You have a ground loop and/or an open ground.
To test for a grounding problem connect the scope probe ground clip to the probe tip. Without touching the probe tip to anything, place it close to where you would probe in your circuit. If you pick-up a lot of hum, then there is a strong magnetic field from a transformer or such coupling into the loop formed with the ground clip. Reduce the exposed area using a high frequency ground clip, and/or add magnetic shielding.
Touch the probe tip to the device under test circuit common with the probe ground clip still in contact witht the probe tip. If you still pick-up a lot of mains voltage, then check the green wire grounds of the scope and any mains powered gear in the circuit under test. With the AC power OFF use a DMM to check the resistance between the probe common of the oscilloscope and the circuit common of the circuit being tested. If there is anything more than an Ohm or two find out why and correct the problem.
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My question is than what setup (1x,10x...) to use when. Currently I have my probes permanently set to 10x. Any general rule?
Most DSOs default to 10x probe input unless you change the setting in the channel menu (or it detects the probe attenuation from the more expensive probes with that function). Most of the time you will use 10x attenuation on the probe. Obviously the scope setting and the probe setting should match or you will get wrong values on the display. Sometime for very weak signals you might use 1x probe and channel values.
Next question - would it make sense to use de-coupling 1pf capacitor - sometimes I do use 1pF 5% 1KV - but to be honest I do not see much difference on the screen when using it.
It depends on what you are measuring and just exactly how you have your "decoupling" capacitor connected. Are you trying to get rid of some high frequency noise riding on your signal of interest?
I am planning to buy 100x probe. - yes/no? suggestions?
I recently bought a very cheap Chinese 100x probe and it is very handy, I would not be able to make measurements on some of the current projects I'm working on without it. This is the one I bought
http://www.ebay.com/itm/High-Voltage-2KV-2000V-Oscilloscope-Scope-Passive-Clip-Probe-100MHz-100X-P4100-/301521247426 (http://www.ebay.com/itm/High-Voltage-2KV-2000V-Oscilloscope-Scope-Passive-Clip-Probe-100MHz-100X-P4100-/301521247426)
But there are much better probes available if you want to spend the money. You probably will want a higher bandwidth probe like
http://www.ebay.com/itm/100X-P4250-High-Voltage-2KV-2000V-Oscilloscope-Scope-Passive-Clip-Probe-250MHz-/291119544514 (http://www.ebay.com/itm/100X-P4250-High-Voltage-2KV-2000V-Oscilloscope-Scope-Passive-Clip-Probe-250MHz-/291119544514)
or
http://www.ebay.com/itm/B-K-Precision-PR2000B-200-MHz-2-kV-Oscilloscope-High-Voltage-Probe-/321660974891 (http://www.ebay.com/itm/B-K-Precision-PR2000B-200-MHz-2-kV-Oscilloscope-High-Voltage-Probe-/321660974891)
I am actually using my 100x probe to make measurements that exceed its rated 2kV voltage rating; I am getting away with this because of the very short duration of the 3.5 kV or higher spikes in the EMJ-Meyer circuit. If I were trying to measure a sine or square wave or DC of that amplitude, like on a charged capacitor .... no way I would risk it.
TK, you was talking about integration MATH function, what is that good for?
Integration gives you the "area under the curve" of a waveform. If you multiply a Voltage trace times a Current trace to produce an Instantaneous Power trace, each point on that trace gives you the instantaneous power of your measurement at that time, in Watts. Now, if you Integrate that trace, your answer is in Watts x seconds, or Joules. So the integration of an instantaneous power trace gives you a measure of the Energy that has passed your measurement point up to that time. It is essentially "adding up" all of the instant power measurements to give an answer in units of Joules, or energy, up to the time of integration.
Here's an EEVblog video where Dave gives a demonstration. Unfortunately he just integrates a Current trace instead of the full VxI trace, so don't let that confuse you.
https://www.youtube.com/watch?v=Dh0xYu8YvaE (https://www.youtube.com/watch?v=Dh0xYu8YvaE)
50Hz modulation from the main- is it big issue? any chance to filter it out?
Thanks.
Usually by properly grounding the probe you will not be plagued by picking up the mains frequency. But I'm sure you've seen what happens when you have a "floating" probe that's not connected to anything, and you touch the tip with your finger, you often will see a 50 Hz (or here in the USA 60 Hz) signal that can appear to be very strong in amplitude. If you suspect that you may have some mains frequency riding on your signal of interest, you can switch the scope's Trigger Coupling (or Source) to "line" (or "mains") and this will cause it to trigger at the mains frequency. Of course you should set your timebase slow enough to see a 50 or 60 Hz signal in this case. How to get rid of it? Use proper grounding and shielding. As I said, if the probe itself is properly grounded by connecting the probe's ground reference lead to the right place in your circuit you should not have troubles. Don't forget that all the probe grounds (I usually call them "references") are connected together at the scope's chassis and therefore back to the mains cord grounding pin and therefore to any other grounded equipment on the same mains circuit.
I'm sure MarkE will also have some good data and advice, my comments come from my experience mostly but MarkE is much better at explaining the operational theory than I am.
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Here's a couple of pictures of what happens using a scope probe the way it is designed to be used versus the way that most everyone uses them using the 6" ground clip. The source signal is 5V CMOS that rises in about 400ps: It's very ordinary stuff. The TEK probe when used coaxially exhibits a fairly clean result with only a couple % artifacts rms to 15ns and then almost nothing after that. However, using the ground clip, the artifacts go up to +/-20% peak and don't ring out until beyond 50ns. This sort of thing can really mess up measurements especially if one is measuring narrow spikes.
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Yep. Most cheap probe kits that I've seen don't even include coaxial adapters, but a couple of my better probes did come with them. Unfortunately they only fit those particular probes.
I see that the cheap probes from China are now at least including some of the little spring-point thingies as alternative ground connections.
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I guess I should repost this video here. Just moving the ground clip a few inches along a wire in the circuit makes a radical difference in the trace.
http://www.youtube.com/watch?v=KWDfrzBIxoQ
(The current probe used in this video cost over 3000 dollars, new. I wish it was mine!)
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I guess I should repost this video here. Just moving the ground clip a few inches along a wire in the circuit makes a radical difference in the trace.
http://www.youtube.com/watch?v=KWDfrzBIxoQ (http://www.youtube.com/watch?v=KWDfrzBIxoQ)
(The current probe used in this video cost over 3000 dollars, new. I wish it was mine!)
This is the kind of thing that scares me about scopes. This is why I wanted to get a simple fg to produce known traces on the scope so I could see what they are supposed to look like. I have learned here that most of the time, you use the 10x settings on the probes. This is good info but...do we use that in our calculation of voltage and current when reading the traces?
In other words....I am on 1 volt/div. and the trace shows a peak of 3 divs. I am on 10x probe setting. Does this mean I am seeing 3 volts? 30 volts? Or
.3 volts? My scope (tek 2213) has the manual pouch bolted to the top of the case, which I did not like at first however, the manual did survive with the unit from the 80's so...it was a good idea. I have read this many times but there are some simple things I can not figure out...the probe setting being one of them.
The other is, and this has been mentioned above by Mark as a possible source for bad readings, is where does the ground clip go in your circuit being tested?
If testing a simple JT circuit, do you probe the + output and clip the ground clip to the minus side of the battery?
If this topic is meant to be o'scopes 101, perhaps I should begin at a remedial level and work my way up from there?
Bill
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Thanks TK, guys .
Very educational this thread.
I have no much electro experience, so measuring principles are a pain in an ars for me. Some tutorial like yours TK are very helpful. There is not many of such on YouTube.
Tell me please, is there situation when you measure just with one probe-end connected- no ground connected and what does it actually show that way? I know when I connect some coil just on main probe-no ground, it shows me around 50-60Vpp amplitudes of whatever it catch from the air.
If I good understand , the correct measurement are performed if you exactly match the impedance of the probe/scope? Would that my de-coupling 1pf cap work here in this case- ?:) I guess it would as the ringing is the mater of the capacitance of the wire.
TK- just thinking to get this probe. What is your opinion? http://www.ebay.com/itm/High-Voltage-5KV-5000V-300MHz-Oscilloscope-Scope-Passive-Clip-Probe-100X-P2300C/281598591049?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dfbc3c9e6d2d743809e66c027e2f7b290%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D301521247426&rt=nc -this is what I do not understand- can my scope + this 5KV probe (100x) withstand that 5KV voltage, or does my oscilloscope must also support some more higher voltage?
Thanks
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Good topic!
As for SG on the 'cheap' I have recently bought this (http://www.ebay.com/itm/UDB1005S-Function-Signal-Generator-Source-Frequency-Counter-DDS-Module-Wave-5MHz/321418276142?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28772%26meid%3D760122cbcbc04a939f4ef777bd9afdce%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D321210132360&rt=nc) type of DDS generator. :)
Very capable, small, handy and very affordable!
This is a complete DDS signal source, Adopts DC5V power supply, can output the sine wave, square wave
(Duty cycle Can be adjust from1% -99%) , triangle wave and sawtooth wave and various function wavefrom,
maximum output can reach up to 10 Vpp, frequency range from 0.01 Hz-5 MHz .
Resolution for 10 MHz, with TTL synchronization output and 60 MHz frequency meter.
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This is SG I use http://www.ebay.ie/itm/321157000855?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649. I am very happy with it.
I am also isolating it through the opto-couple.
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This is the kind of thing that scares me about scopes. This is why I wanted to get a simple fg to produce known traces on the scope so I could see what they are supposed to look like. I have learned here that most of the time, you use the 10x settings on the probes. This is good info but...do we use that in our calculation of voltage and current when reading the traces?
In other words....I am on 1 volt/div. and the trace shows a peak of 3 divs. I am on 10x probe setting. Does this mean I am seeing 3 volts? 30 volts? Or
.3 volts? My scope (tek 2213) has the manual pouch bolted to the top of the case, which I did not like at first however, the manual did survive with the unit from the 80's so...it was a good idea. I have read this many times but there are some simple things I can not figure out...the probe setting being one of them.
Bill, doesn't your 2213 have the same kind of vertical range knobs and markings as the 2213a? The markings should be self-explanatory... if you use a 10x probe you read the value under the "10x probe" marking and that's what you get on the graticule. See the image below for the switch markings...
My old HP180 does not have markings like this, so if I use a 1x probe setting, the switch marking is what I get on the graticule. If I use a 10x probe setting, I have to mentally multiply the switch marking by 10 to get the graticule value.
The other is, and this has been mentioned above by Mark as a possible source for bad readings, is where does the ground clip go in your circuit being tested?
If testing a simple JT circuit, do you probe the + output and clip the ground clip to the minus side of the battery?
The probe gives you the voltage between the clip and the tip. That's why I call the ground clip the "reference" because it doesn't necessarily have to be at the "ground" of the circuit under test. (For most scopes the clip IS grounded to the mains ground though). All the probe references should be connected to the same point though, and if the circuit under test is actually grounded, this should be the connection point of the probe references as well, otherwise you set up a groundloop condition. But with a battery powered, ungrounded circuit like a JT, you can connect the "ground" of the probe at whatever point you want to use as a reference for the tip voltage.
If this topic is meant to be o'scopes 101, perhaps I should begin at a remedial level and work my way up from there?
Bill
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This is the kind of thing that scares me about scopes. This is why I wanted to get a simple fg to produce known traces on the scope so I could see what they are supposed to look like. I have learned here that most of the time, you use the 10x settings on the probes. This is good info but...do we use that in our calculation of voltage and current when reading the traces?
In other words....I am on 1 volt/div. and the trace shows a peak of 3 divs. I am on 10x probe setting. Does this mean I am seeing 3 volts? 30 volts? Or
.3 volts? My scope (tek 2213) has the manual pouch bolted to the top of the case, which I did not like at first however, the manual did survive with the unit from the 80's so...it was a good idea. I have read this many times but there are some simple things I can not figure out...the probe setting being one of them.
The other is, and this has been mentioned above by Mark as a possible source for bad readings, is where does the ground clip go in your circuit being tested?
If testing a simple JT circuit, do you probe the + output and clip the ground clip to the minus side of the battery?
If this topic is meant to be o'scopes 101, perhaps I should begin at a remedial level and work my way up from there?
Bill
Virtually all oscilloscopes let you tell them what the probe attenuation is, so that they display scaled to the original signal input. On older scopes, they took advantage of the 1/2/5X progression of the attenuation steps. A marker showed the gain for 1X three dial steps away from the marker for the 10X.
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Thanks TK, guys .
Very educational this thread.
I have no much electro experience, so measuring principles are a pain in an ars for me. Some tutorial like yours TK are very helpful. There is not many of such on YouTube.
Tell me please, is there situation when you measure just with one probe-end connected- no ground connected and what does it actually show that way?
All voltage measurements are across two nodes. When you connect just the probe tip to the circuit, the other side of the measurement is whatever potential the outside barrel of the scope input happens to be at. It may bear very little relation to anything specific in the circuit you want to measure. The probe cable itself is an antenna. I know when I connect some coil just on main probe-no ground, it shows me around 50-60Vpp amplitudes of whatever it catch from the air.
If I good understand , the correct measurement are performed if you exactly match the impedance of the probe/scope?
That is never the case using the common high impedance passive probes that most folks use. The idea there is for the probe to impose as little effect on the circuit under test as possible. Would that my de-coupling 1pf cap work here in this case- ?:) I guess it would as the ringing is the mater of the capacitance of the wire.
1pF is very small in the context of a passive oscilloscope probe. The cable back to the scope has 50pF - 100pF of parasitic capacitance. Another 1pF won't make much of a difference.
TK- just thinking to get this probe. What is your opinion? http://www.ebay.com/itm/High-Voltage-5KV-5000V-300MHz-Oscilloscope-Scope-Passive-Clip-Probe-100X-P2300C/281598591049?_trksid=p2047675.c100005.m1851_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dfbc3c9e6d2d743809e66c027e2f7b290%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D301521247426&rt=nc -this is what I do not understand- can my scope + this 5KV probe (100x) withstand that 5KV voltage, or does my oscilloscope must also support some more higher voltage?
Thanks
That probe looks OK. Here it is shipped from within the US: http://www.ebay.com/itm/Brand-New-Oscilloscope-Clip-Probe-P2300C-300MHz-5000V-5KV-High-Voltage-100X-/120878612465?pt=LH_DefaultDomain_0&hash=item1c24ed3ff1
The probe divides the input voltage by 100:1. 5KV at the probe tip becomes 50V at the input to the oscilloscope. If your oscilloscope handles +/-50V then you can use the probe with voltages up to 5kV with the caveat: The 5kV must be the peak measured voltage. The ground clip introduces ringing that increases the measured voltage. If your oscilloscope only handles a smaller voltage like +/-20V then the peak measured voltage that you can safely probe is +/-2kV.
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Thanks TK, guys .
Very educational this thread.
I have no much electro experience, so measuring principles are a pain in an ars for me. Some tutorial like yours TK are very helpful. There is not many of such on YouTube.
Tell me please, is there situation when you measure just with one probe-end connected- no ground connected and what does it actually show that way? I know when I connect some coil just on main probe-no ground, it shows me around 50-60Vpp amplitudes of whatever it catch from the air.
If I good understand , the correct measurement are performed if you exactly match the impedance of the probe/scope? Would that my de-coupling 1pf cap work here in this case- ? :) I guess it would as the ringing is the mater of the capacitance of the wire.
TK- just thinking to get this probe. What is your opinion? http://www.ebay.com/itm/High-Voltage-5KV-5000V-300MHz-Oscilloscope-Scope-Passive-Clip-Probe-100X-P2300C/281598591049?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dfbc3c9e6d2d743809e66c027e2f7b290%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D301521247426&rt=nc (http://www.ebay.com/itm/High-Voltage-5KV-5000V-300MHz-Oscilloscope-Scope-Passive-Clip-Probe-100X-P2300C/281598591049?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dfbc3c9e6d2d743809e66c027e2f7b290%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D301521247426&rt=nc) -this is what I do not understand- can my scope + this 5KV probe (100x) withstand that 5KV voltage, or does my oscilloscope must also support some more higher voltage?
Thanks
That looks like a probe you could actually use for real signals up to 5kV all right.
The probe attenuates the voltage to the scope's input. The scope's published input voltage limit assumes no attenuation, I think. So I think that if your scope says "400 volts" as the channel input limit, that means 400 V maximum actual signal with a 1x probe or direct connection. I THINK. I hope MarkE can give his input here.
Yes, the probe attenuation and the scope's channel input setting should match, otherwise the voltage readings will not be accurate. Yes, if your ground clip isn't connected to anything then you can pick up all kinds of crazy stuff, but sometimes the probe is adequately grounded anyway through the scope chassis and the mains power cord, so it can work in certain cases.
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Bill, doesn't your 2213 have the same kind of vertical range knobs and markings as the 2213a? The markings should be self-explanatory... if you use a 10x probe you read the value under the "10x probe" marking and that's what you get on the graticule. See the image below for the switch markings...
My old HP180 does not have markings like this, so if I use a 1x probe setting, the switch marking is what I get on the graticule. If I use a 10x probe setting, I have to mentally multiply the switch marking by 10 to get the graticule value. The probe gives you the voltage between the clip and the tip. That's why I call the ground clip the "reference" because it doesn't necessarily have to be at the "ground" of the circuit under test. (For most scopes the clip IS grounded to the mains ground though). All the probe references should be connected to the same point though, and if the circuit under test is actually grounded, this should be the connection point of the probe references as well, otherwise you set up a groundloop condition. But with a battery powered, ungrounded circuit like a JT, you can connect the "ground" of the probe at whatever point you want to use as a reference for the tip voltage.
TK:
OK, now I feel even more stupid. I just looked at my scope and....sure enough, there is a designation for 1x and 10x. I never noticed that before.
Thank you so much.
Bill (my face is still red)
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If you already have some programming experience but just not with c, or even if you don't, probably the best way to learn is just to look at example sketches and start changing them and see what happens. It's really pretty easy to do the basic stuff, the Arduino IDE comes with a lot of basic example sketches. Most people start with the "blink" sketch which just blinks an LED. The Arduino online references are excellent and the programming interface is portable, runs on any computer OS, so you can write your sketches on a Mac, load them with Linux, run and display serial data on Windoze etc.
Here's a handy thing I made:
http://www.youtube.com/watch?v=S6N8ys8FiA4
And just to steer back to the topic of oscilloscopes, here's a scoposcopy video showing how the Inductometer does its magic:
http://www.youtube.com/watch?v=Qx3B89379eQ
TK-
I have a little experience with HTML5 but that's about it, and it's been a few years since I've done anything with it. I need an LCD and I have plenty of them laying around from things I took apart, and it looks quite easy to mod one to use for the duino. I just need to find an instructional and i'll be good to go! Then the first thing I am going to make is definitely that LC meter! I don't have an LCR meter. Definitely perfect timing on your part with posting that vid and info! haha Thanks for that!
I went and picked up that scope today, and it certainly needs some TLC. First of all, the only "working" probe it has is an original and it definitely has at the very least one short in it. feels like a break in the coax center wire, and there are a few spots where the sheathing is nicked and shielding exposed. It sat in a workshop that doesn't have very good humidity control (a basement) for 9+ years, so when turning some of the knobs, the trace flickers.
First thing I'm going to do before I do anything more than open it for a look is order at least one new probe and wait for that to get here so I can really see what else might be wrong. Channel two does put a trace on the screen, but whatever is wrong with it is making it look like the trace is "driving" across the CRT at 100mph. She's definitely getting a restore job.... gotta get a can of de-ox it and some IPA. Found a thing off EEVblog of someone fully restoring the exact scope that I have, so that should help a little. Oh, and it came with the original service manual as well. Got the GR 1330-A, and ended up with a 1000W kenwood excelon amp, too.
Anyone have any suggestions or references that may be helpful?
[edit]
I've got everything out here on the table, other than the scope itself. I did a continuity test on the lead I used to check the scope while I was there, and it's shorted to the max. even the ground is somewhat shorted. That may have been the only thing causing the trace to go haywire on me, so I'm glad I took it regardless. I have one lead connector/cable here that is in great condition, and it's for the probe I linked to below. I have almost all the parts for it. What's missing is the little button for "GRD REF". Is that going to be a problem? The only real issue with rebuilding it is that I have to reuse a crimp connector piece, but I should be able to re-round it out after I drill out and pick out the remaining wire.
It says it is both 1X and 10X, so I guess that means all I would need to do is flip the switch on the probe lead itself to change..? and of course the setting on the scope, as well.
http://www.ebay.com/itm/TEKTRONIX-OSCILLOSCOPE-TEST-PROBE-10-X-MODEL-P6062A-/351289693035?pt=LH_DefaultDomain_0&hash=item51ca7f536b
( It is that one, but it is selectable between 1X and 10X.)
As for buying new leads, it would make sense to get a set of 4 (two 1X and two 10X) so I can match them on both channels, since I intend to fix channel 2, correct?
It sounds like I should also buy a 100X, 2kv to 5kv probe as well, if I can, right? should I also try to get two of those?
How does that work using a 100X probe when the highest setting on the scope is 10X? Just use 10X setting and multiply all the readouts by 10?
I also would like a confirmation from someone about the 5kv probe and attenuation issue that TK spoke of in his last post. Wouldn't wanna go destroying a perfectly good vintage piece of equipment! haha
Thanks!
Brian
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TK-
I have a little experience with HTML5 but that's about it, and it's been a few years since I've done anything with it. I need an LCD and I have plenty of them laying around from things I took apart, and it looks quite easy to mod one to use for the duino. I just need to find an instructional and i'll be good to go! Then the first thing I am going to make is definitely that LC meter! I don't have an LCR meter. Definitely perfect timing on your part with posting that vid and info! haha Thanks for that!
You'll find plenty of tutorials for adapting certain surplus LCDs to the Arduino. The disadvantage is that they will need six or seven data lines to work, taking up output pins on the 'duino. That's why I like the Parallax brand serial LCDs, they only need one data line, and the two power leads, to give full functionality including the built in piezo speaker and backlight control.
I'm glad you find the Inductometer interesting! You can also make a capacitance meter with essentially the same circuit simply by using a known inductance instead of the known capacitance standard, and changing the sketch math a little bit. You don't actually need the LCD display; if you keep the Arduino plugged into your computer with the USB cable you can use the serial monitor in the Arduino IDE and put Serial.print statements in your sketch to give you the readout on your computer in real-time.
I went and picked up that scope today, and it certainly needs some TLC. First of all, the only "working" probe it has is an original and it definitely has at the very least one short in it. feels like a break in the coax center wire, and there are a few spots where the sheathing is nicked and shielding exposed. It sat in a workshop that doesn't have very good humidity control (a basement) for 9+ years, so when turning some of the knobs, the trace flickers.
First thing I'm going to do before I do anything more than open it for a look is order at least one new probe and wait for that to get here so I can really see what else might be wrong.
You can always use a direct connection with a patch cord from your signal generator to the scope channel. This will be equivalent to using a 1x probe. Strictly speaking I suppose you should use a 50 ohm impedance BNC patchcord with a T-fitting and a 50 ohm terminator at the scope input, but just a straight patchcord will work fine for low frequencies and casual testing.
Channel two does put a trace on the screen, but whatever is wrong with it is making it look like the trace is "driving" across the CRT at 100mph. She's definitely getting a restore job.... gotta get a can of de-ox it and some IPA. Found a thing off EEVblog of someone fully restoring the exact scope that I have, so that should help a little. Oh, and it came with the original service manual as well.
That's good, maybe it's just a trigger problem or even just dirty switch contacts. The fact that you get a trace at all on CH2 is really good news!
Got the GR 1330-A, and ended up with a 1000W kenwood excelon amp, too.
Anyone have any suggestions or references that may be helpful?
I love that old General Radio gear! There is nothing like it, their designers were truly geniuses in those days. I found a manual for your oscillator, attached below. It looks like it has those weird type 847 "bisexual" connectors, you might like to look around for BNC adapters for those things. The tubes aren't too weird, you can probably find replacements on the market, although I haven't looked. Svetlana is a possible source for new tubes if you need them.
[edit]
I've got everything out here on the table, other than the scope itself. I did a continuity test on the lead I used to check the scope while I was there, and it's shorted to the max. even the ground is somewhat shorted. That may have been the only thing causing the trace to go haywire on me, so I'm glad I took it regardless. I have one lead connector/cable here that is in great condition, and it's for the probe I linked to below. I have almost all the parts for it. What's missing is the little button for "GRD REF". Is that going to be a problem? The only real issue with rebuilding it is that I have to reuse a crimp connector piece, but I should be able to re-round it out after I drill out and pick out the remaining wire.
It says it is both 1X and 10X, so I guess that means all I would need to do is flip the switch on the probe lead itself to change..? and of course the setting on the scope, as well.
http://www.ebay.com/itm/TEKTRONIX-OSCILLOSCOPE-TEST-PROBE-10-X-MODEL-P6062A-/351289693035?pt=LH_DefaultDomain_0&hash=item51ca7f536b (http://www.ebay.com/itm/TEKTRONIX-OSCILLOSCOPE-TEST-PROBE-10-X-MODEL-P6062A-/351289693035?pt=LH_DefaultDomain_0&hash=item51ca7f536b)
( It is that one, but it is selectable between 1X and 10X.)
Those old Tek probes are fine but you might find them harder to repair than you think. I have a couple similar ones that I never use, they are just too clunky compared to modern probes. Yes, the selection switch setting should match the scope's setting for attenuation. I don't know if the scope will autodetect that probe's setting or not, but you'll figure that out soon enough. ( Actually it should autodetect this probe, according to the spec sheet.) The missing GND REF button should not be a problem as long as it isn't stuck in "grounded" mode! I don't know if you have the spring clip tip adapter... this is almost a necessity so that you can clip the probe in place and then free up your hands. New probes will have clip adapters included with the kit.
As for buying new leads, it would make sense to get a set of 4 (two 1X and two 10X) so I can match them on both channels, since I intend to fix channel 2, correct?
Almost every modern probe you will find will have a 1x/10x switch so there is no need to buy separate probes for that. Pool your money and just buy 2 higher-quality probes for the price of 4 lower-quality ones.
It sounds like I should also buy a 100X, 2kv to 5kv probe as well, if I can, right? should I also try to get two of those?
How does that work using a 100X probe when the highest setting on the scope is 10X? Just use 10X setting and multiply all the readouts by 10?
Yes, use the 10x setting on the scope and mentally multiply your graticule readings by 10. So the "20 v/div" range becomes 200 v/div with the 100x probe.
I can't imagine why you would actually need two high-bandwidth 5kV probes.... or at least I've only ever felt the need for one HV probe myself --- so I'd say "it depends". If you do need a second one you can always get it when you need it.
I also would like a confirmation from someone about the 5kv probe and attenuation issue that TK spoke of in his last post. Wouldn't wanna go destroying a perfectly good vintage piece of equipment! haha
Thanks!
Brian
I think MarkE already said pretty much the same thing I said about the scope's input voltage limit and the probe attenuation; the input limit spec is raw, that is, not attenuated. So the 100x probe reduces the actual voltage from the signal by 100x at the scope's input jack. So if you have a 400 v input limit (as my Tek2213a does) then you are totally good to go with your 5 kV 100x probe because you'll reach the probe's limit far before you reach the scope's limit. 5 kV signal will mean only 50 V at the scope input, and a scope setting of 50 v/div (10x) will give you 500 v/div with the 100x probe and you'll run out of screen height before you hit either the probe or the scope limits.
But you had better know what you are doing if you are really intending to work with voltages that high! You don't get to make many mistakes with voltages like that. Keep one hand in your pocket while working with those voltages so you don't accidentally take a shock across your chest.
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You'll find plenty of tutorials for adapting certain surplus LCDs to the Arduino. The disadvantage is that they will need six or seven data lines to work, taking up output pins on the 'duino. That's why I like the Parallax brand serial LCDs, they only need one data line, and the two power leads, to give full functionality including the built in piezo speaker and backlight control.
I'm glad you find the Inductometer interesting! You can also make a capacitance meter with essentially the same circuit simply by using a known inductance instead of the known capacitance standard, and changing the sketch math a little bit. You don't actually need the LCD display; if you keep the Arduino plugged into your computer with the USB cable you can use the serial monitor in the Arduino IDE and put Serial.print statements in your sketch to give you the readout on your computer in real-time.
Good to know, I will aim to just buy a Parallax LCD, and in the meantime just use the serial monitor. And if for some reason I run across a situation where I need it away from my PC, then I will spend the time turning one of my lcd's into a screen.
You can always use a direct connection with a patch cord from your signal generator to the scope channel. This will be equivalent to using a 1x probe. Strictly speaking I suppose you should use a 50 ohm impedance BNC patchcord with a T-fitting and a 50 ohm terminator at the scope input, but just a straight patchcord will work fine for low frequencies and casual testing. That's good, maybe it's just a trigger problem or even just dirty switch contacts. The fact that you get a trace at all on CH2 is really good news!
I don't have any of that stuff on hand, so if I need to hook anything up to the scope before I have a working probe I would have to just do the straight patch cord method you mentioned. I'd rather just wait for a probe, though. As for the BNC cord, T-fitting, and terminator.... I won't need any of that stuff when I have probes, will I? or would it come in handy to have it anyway? It seems that it's extremely inexpensive stuff to get, like $10 with shipping and I'll have 2 of each. For now I'm just going to put my money towards probes, though. Maybe I'll run across some of that stuff in the piles of stuff in my basement... or get it from the Comcast guy if I see him around.
I love that old General Radio gear! There is nothing like it, their designers were truly geniuses in those days. I found a manual for your oscillator, attached below. It looks like it has those weird type 847 "bisexual" connectors, you might like to look around for BNC adapters for those things. The tubes aren't too weird, you can probably find replacements on the market, although I haven't looked. Svetlana is a possible source for new tubes if you need them.
Thanks for the manual! I'll have to read it and learn what I can use it for before I mess with it. The guy I got it off of told me that it used to be used to push a signal thru the radio comm gear as a way to diagnose problems with it. All the tubes are good, and we took the case off... the thing is SPARKLINGLY, squeaky clean inside!! MINT condition! I'll definitely see what I can find as for adapters for the 847 connectors. The pics I've seen of these things for sale just showed gator clips as output connections. It's too bad it didn't come with the cables!! I've never seen one thus far that had them, though.
The missing GND REF button should not be a problem as long as it isn't stuck in "grounded" mode!
It doesn't appear to be. I'm going to attach a pic below of a close up of the switch contacts with a couple questions.
I don't know if you have the spring clip tip adapter... this is almost a necessity so that you can clip the probe in place and then free up your hands. New probes will have clip adapters included with the kit. Almost every modern probe you will find will have a 1x/10x switch so there is no need to buy separate probes for that. Pool your money and just buy 2 higher-quality probes for the price of 4 lower-quality ones.
No, the 6062A does not come with the spring loaded part, but it does have the hook adapter. Maybe I can rig something up with a small piece of plastic tube from the pieces of the Fluke probe and put a little spring on it for the time being, until I can find that part online somewhere. Hopefully I can find a spring loaded hook tip adapter for this probe for cheap...
That's good to know, I will make sure I find a pair that has the switch, and I'll get the best ones that I can afford.
Yes, use the 10x setting on the scope and mentally multiply your graticule readings by 10. So the "20 v/div" range becomes 200 v/div with the 100x probe.
So if you have a 400 v input limit (as my Tek2213a does) then you are totally good to go with your 5 kV 100x probe because you'll reach the probe's limit far before you reach the scope's limit. 5 kV signal will mean only 50 V at the scope input, and a scope setting of 50 v/div (10x) will give you 500 v/div with the 100x probe and you'll run out of screen height before you hit either the probe or the scope limits.
So then since my scope has an 8 x 10 grid, and at 10X setting it's max setting will be 50v/div (500v/div), I won't be able to read anything over 4kV with the zero-plane at the very bottom (or top) of the screen, correct? So with zero in the middle, I'll see 2kv pos and neg.
Since a lot of these devices that we mess with and test deal with HV spikes, I feel I should get a HV probe. But if I find a pair of standard probes that are a high jump in quality that I can afford if I don't get the HV probe, I will just get it later. Not to mention I should hold onto some funds in case I have to buy something to repair channel 2. While I consider what I should buy, I'm going to continue trying to rebuild this 6062A probe (which appears to be a $100 probe, so worth the effort). Also, I would like to replace the cable on the 6065A probe. Any suggestions on what the specs should be for a replacement coax cable?
I attached the pic of the probe switch I mentioned before. My questions:
The GRD REF button appears to break the connection from PT3 to PT2 and connect to PT 5 when pressed. is this correct?
Probe tip to PT 1 has a direct connection. very little resistance.
Probe tip to PT 3 has a connection reading 9.06MegOhm resistance.
From the leftover solder/residual flux, it appears there was a connection to PT 6 of the switch.
From the residual flux, it appears there may have also been a connection to PT 1 of the switch.
When I opened the cover of the connector that goes to the scope, it appears that, in addition to the ground (shielding, which appears to be soldered directly to the metal housing) there are two wires. ( I will have to dissect the probe end and find the second wire... probably just a matter of cutting back the insulation and ground shielding far enough)
Inside the housing, the main super-fine wire in the middle goes to what I'm assuming to be a capacitor, though it is in the shape of a resistor. My meter doesn't read any resistance, and the capacitance it shows is about 0.015nF. So there's my 10X wire.
The other wire, which is outside the shielding for the middle (in the case) goes to a tiny resistor which reads 11.56Kohm.
There is also a 95.3ohm 1% resistor with a tiny, tiny capacitor across it, which on one end connects to the post for the center output pin (also connected to the capacitor for the 10X wire) which connect on the opposite end to the adjuster pot(?) which has a connection to ground.
I now know what you mean by how much of a PITA it is to rebuild these probes..... but I'm going to do it anyway. I just need to know where to connect what....
I am also missing one screw in addition to the grd ref button. I'm sure I can find a replacement in my container filled with screws from things I took apart, and cut it down to the proper length. If the button would be useful, I'll widdle a new one out of some scrap plastic....
TK - do you have a link to that info you were referencing about the probe? A diagram of the connections would be extremely useful....! hahaha
Sorry for all the questions on this... I just want to make sure I do it right the first time around, so I don't have to take it all back apart and try again, and again.
Thanks!!
Brian
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@Brian:
The GND switch is supposed to break the scope's connection to the probe tip and connect it to the cable's ground conductor instead, but without connecting the probe tip to ground so you don't short out your circuit under test. This is so that you can easily identify which trace is which on a multi-trace display, by temporarily grounding the probe while it is in position for a measurement. I can't tell you what connects to what on the switch from here, though. And I haven't been able to find a "free" copy of the probe's manual, although it's easy to find them for sale.
Some of these better probes don't use a regular coax cable. Instead they have a shielded cable that has a very thin nichrome wire as the center conductor and it is practically impossible to work with this wire, as it can't easily be soldered due to the alloy, and it is so thin it is hard to handle physically as well, for crimps and such. I don't know if your probe has this type of coax or not.
It's always a good idea to have a few BNC patch cables around, plus adapters (BNC to GR874, BNC to the CB-type connectors SO-239 or PL-259, BNC to RCA phono jack) and a 50 ohm BNC terminator and a T or two. You will eventually want to connect your GenRad oscillator to the scope, and doing it with a probe is clumsy. For example you may want to use the GenRad to trigger the scope thru the scope's Ext Trig input as well as feeding the same signal to a circuit, and use both probes on the circuit for traces at some point. So you'll need a patch cable, a T, the 874 adapter, and another cable with BNC on one end and clips on the other end for that hookup.
http://www.ebay.com/itm/BNC-to-mini-grabber-test-clips-Pomona-2-sets-80cm-lead-/290533726392 (http://www.ebay.com/itm/BNC-to-mini-grabber-test-clips-Pomona-2-sets-80cm-lead-/290533726392)
Hopefully you can find the GR874 adapter cheaper than this somewhere:
http://www.ebay.com/itm/like/351136777620?lpid=82&chn=ps (http://www.ebay.com/itm/like/351136777620?lpid=82&chn=ps)
http://en.wikipedia.org/wiki/GR_connector (http://en.wikipedia.org/wiki/GR_connector)
Yes, you've got the scope vertical scaling issue correct.
I'd suggest you to get two decent 1x/10x probes and one 100x probe, plus at least one 6 foot BNC 50-ohm patch cable, an adapter for the GR connector, a few BNC adapters and fittings, like one that you can use to connect a probe to the patch cable (this is double-female I think, I am always confused about BNC gender assignments), a T fitting, and a BNC 50 ohm terminator that will fit on the T fitting. These things are available in assorted gender combinations, so try to get some that are compatible so you can string them together as needed.
Here's a pic of most of my adapter stash (others are fairly permanently connected to my RM503 scope which has the SO-239 panel connectors) :
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yeah, I think you're right on that... It probably is nichrome wire. Especially since it's so fine. I looked up "nichrome soldering" and apparently it can be done fairly easily with acid flux and silver solder. there were a few other people who said HCl based flux or Zinc Chloride flux.
Other than the probe issues, I really hope that all this scope needs is a good cleaning/deoxing.... I really don't want to get into replacing parts on it, but obviously will if I must.
Thanks for all the help TK, and I will definitely do my best to get all of the BNC adapters and the 874 adapters. I'm going to check around with some places/people I know of that deal in antiques and antique electronics stuff around town before I order anything. Also going to check with the RF engineer that I met when I was out playing pool a few months back. Hopefully he can hook me up! That is definitely quite a taxing for only one fitting..
Another thing about the connections, other than the two 874 outs (one for audio one for RF) there are also two banana plug females that double as the screw posts. I'm not sure if these are meant as some sort of ground or are an alternate out, so I'll have to look into that in the pdf you sent me. Rob, the guy I got it from, also sent me the same PDF plus a PDF of "the general radio experimenter" magazine/pamphlet from 1950!! :)
I really appreciate you taking the time to help me with all this. In the future if there's anything I can do to help you out, let me know.
Brian
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I'm an idiot. I had the manual for the 6062A this whole time. right inside the front cover of the service manual. If only I would have bothered to open it........... A day worth of headache could have been entirely avoided.
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It appears that the "Modify" button has disappeared, so I can't just edit my last post.
Sorry for my own stupidity in not checking the materials that I already have to see if I had the info that I needed before going and asking a bunch of unnecessary questions and taking up people's valuable time to read/reply to them.
When I'm to a point where I know what I am doing, I will pay it forward and teach the next guy since you all are taking your time to teach me. That's only fair. Then when I am incorrect about something or leave out important info, you will only then have to take the time to add a little info.
Brian
[edit] - ahh I see now, apparently after a certain amount of time has passed, you are unable to edit your posts anymore... [end-edit]
- I am looing at probes to order, and from what I gather, the lower the model number, the higher the quality??
Here are my options for the standard 1x/10x probes:
---T5100 - http://www.ebay.com/itm/HQRP-100MHz-Oscilloscope-Probes-fits-Tektronix-HP-T5100-X1-X10-New-/221690519344?pt=LH_DefaultDomain_0&hash=item339dc8df30
---P6100 - http://www.ebay.com/itm/Two-x1-x10-100MHZ-Oscilloscope-clip-probes-HP-Tektronix-/290374567712?pt=LH_DefaultDomain_0&hash=item439bac4720
---TP6100 - http://www.ebay.com/itm/Two-Oscilloscope-Scope-analyzer-Clip-Probe-x1-x10-100MHz-Kit-For-Tektronix-HP/291177486377?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29170%26meid%3D8ad8e434a92c4ee9afad4dbc3106985a%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D220375454020&rt=nc
All of them are 6Mhz/100Mhz except for the P6100's, which are 4Mhz/100Mhz.
All of them are X1 = 150VDC peak; X10 = 300VDC peak, except for the TP6100 which are 300VDC/600VDC.
My scope's Max Input Voltage is (dc coupled) 250V(DC + peak AC) or 500V p-p ac at 1khz or less; (ac coupled) 500V (dc + peak ac) or 500V p-p ac at 1khz or less.
So, if I am correct here, If I want to be able to take advantage of the full ability of my scope with the 1X probe, I would want to choose the TP6100 probes?
Also, as for a HV probe -
http://www.ebay.com/itm/100MHz-High-Voltage-Oscilloscope-Clip-Probe-4000V-Alligator-Clip-Passive-P5100-/111586099163?pt=LH_DefaultDomain_0&hash=item19fb0cbfdb
http://www.ebay.com/itm/Tektronix-013-0290-02-Oscilloscope-Probe-Screw-On-Hook-Clip-Set-P5100-P5120-/321462078021?pt=LH_DefaultDomain_0&hash=item4ad8a20a45
Should I wait til I can afford that one and the spring loaded hook tip, or just get one along the lines of a $30 2kV probe with all the accessories?
I also noticed that none of those probes come with the spring point ground fitting. Is that just something more for HV applications?
Brian
heres a laugh..... a 1,000X 40kV probe....http://www.ebay.com/itm/1000X-P5104High-Voltage-40KV-40000V-20MHz-Oscilloscope-Passive-Probe-Clip-/291119549732?pt=LH_DefaultDomain_0&hash=item43c813cd24 :o
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It appears that the "Modify" button has disappeared, so I can't just edit my last post.
Sorry for my own stupidity in not checking the materials that I already have to see if I had the info that I needed before going and asking a bunch of unnecessary questions and taking up people's valuable time to read/reply to them.
Hey, no problem, don't put yourself down. I'm glad to share what I know, and to learn more from those who know more than I do.
When I'm to a point where I know what I am doing, I will pay it forward and teach the next guy since you all are taking your time to teach me. That's only fair. Then when I am incorrect about something or leave out important info, you will only then have to take the time to add a little info.
Brian
[edit] - ahh I see now, apparently after a certain amount of time has passed, you are unable to edit your posts anymore... [end-edit]
- I am looing at probes to order, and from what I gather, the lower the model number, the higher the quality??
Here are my options for the standard 1x/10x probes:
---T5100 - http://www.ebay.com/itm/HQRP-100MHz-Oscilloscope-Probes-fits-Tektronix-HP-T5100-X1-X10-New-/221690519344?pt=LH_DefaultDomain_0&hash=item339dc8df30 (http://www.ebay.com/itm/HQRP-100MHz-Oscilloscope-Probes-fits-Tektronix-HP-T5100-X1-X10-New-/221690519344?pt=LH_DefaultDomain_0&hash=item339dc8df30)
---P6100 - http://www.ebay.com/itm/Two-x1-x10-100MHZ-Oscilloscope-clip-probes-HP-Tektronix-/290374567712?pt=LH_DefaultDomain_0&hash=item439bac4720 (http://www.ebay.com/itm/Two-x1-x10-100MHZ-Oscilloscope-clip-probes-HP-Tektronix-/290374567712?pt=LH_DefaultDomain_0&hash=item439bac4720)
---TP6100 - http://www.ebay.com/itm/Two-Oscilloscope-Scope-analyzer-Clip-Probe-x1-x10-100MHz-Kit-For-Tektronix-HP/291177486377?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29170%26meid%3D8ad8e434a92c4ee9afad4dbc3106985a%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D220375454020&rt=nc (http://www.ebay.com/itm/Two-Oscilloscope-Scope-analyzer-Clip-Probe-x1-x10-100MHz-Kit-For-Tektronix-HP/291177486377?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29170%26meid%3D8ad8e434a92c4ee9afad4dbc3106985a%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D220375454020&rt=nc)
I think all three of those probe sets are exactly the same probes, just with different labels on them, from the same factory in China even. Don't be fooled by the "for Tektronix" line on the ads... these are just basic low-quality scope probes so you might as well find the cheapest seller. Sure, they are "for Tektronix"... also for Owon, Agilent, Rigol, HP, Siglent, BKprecision, LeCroy ..... get the idea? I bought a couple of these not too long ago, I think at the 16 dollar a pair price point, and they are adequate for what I'm doing. I don't remember if they included the ground springpoint adapter in the package.
But see below.
All of them are 6Mhz/100Mhz except for the P6100's, which are 4Mhz/100Mhz.
All of them are X1 = 150VDC peak; X10 = 300VDC peak, except for the TP6100 which are 300VDC/600VDC.
My scope's Max Input Voltage is (dc coupled) 250V(DC + peak AC) or 500V p-p ac at 1khz or less; (ac coupled) 500V (dc + peak ac) or 500V p-p ac at 1khz or less.
So, if I am correct here, If I want to be able to take advantage of the full ability of my scope with the 1X probe, I would want to choose the TP6100 probes?
I can think of no reason whatsoever that you would want to use a 1x probe on a signal of hundreds of volts amplitude. Generally you will use 10x attenuation all the time, unless the signal is _so small_ that it doesn't read well with the 10x attenuation setting.
Also, as for a HV probe -
http://www.ebay.com/itm/100MHz-High-Voltage-Oscilloscope-Clip-Probe-4000V-Alligator-Clip-Passive-P5100-/111586099163?pt=LH_DefaultDomain_0&hash=item19fb0cbfdb (http://www.ebay.com/itm/100MHz-High-Voltage-Oscilloscope-Clip-Probe-4000V-Alligator-Clip-Passive-P5100-/111586099163?pt=LH_DefaultDomain_0&hash=item19fb0cbfdb)
Looks deadly all right. Not something I would use around here, though; I don't work on high-power commercial radio transmitters much these days. ;)
This is similar to the "P4100" 100x probe that I got, but from a different vendor:
http://www.ebay.com/itm/New-100MHz-2000V-High-Voltage-Oscilloscope-Probes-P4100-/380456973755?pt=LH_DefaultDomain_0&hash=item589500b5bb (http://www.ebay.com/itm/New-100MHz-2000V-High-Voltage-Oscilloscope-Probes-P4100-/380456973755?pt=LH_DefaultDomain_0&hash=item589500b5bb)
http://www.ebay.com/itm/Tektronix-013-0290-02-Oscilloscope-Probe-Screw-On-Hook-Clip-Set-P5100-P5120-/321462078021?pt=LH_DefaultDomain_0&hash=item4ad8a20a45 (http://www.ebay.com/itm/Tektronix-013-0290-02-Oscilloscope-Probe-Screw-On-Hook-Clip-Set-P5100-P5120-/321462078021?pt=LH_DefaultDomain_0&hash=item4ad8a20a45)
YGTBKM ! Fergeddaboudit.
Should I wait til I can afford that one and the spring loaded hook tip, or just get one along the lines of a $30 2kV probe with all the accessories?
I also noticed that none of those probes come with the spring point ground fitting. Is that just something more for HV applications?
No, _not_ generally for HV, more for high _frequency_ testing of circuit boards with chips mounted to them and specific ground pads included to match the spacing of the spring clip.
But the 100x probe that I got from China did come with the spring clip, a surprise.
Brian
heres a laugh..... a 1,000X 40kV probe....http://www.ebay.com/itm/1000X-P5104High-Voltage-40KV-40000V-20MHz-Oscilloscope-Passive-Probe-Clip-/291119549732?pt=LH_DefaultDomain_0&hash=item43c813cd24 (http://www.ebay.com/itm/1000X-P5104High-Voltage-40KV-40000V-20MHz-Oscilloscope-Passive-Probe-Clip-/291119549732?pt=LH_DefaultDomain_0&hash=item43c813cd24) :o
LOL.
But your scope is a higher bandwidth scope. You probably should be looking for 200 MHz probes instead of the cheaper 100 MHz if you want to take advantage of the high frequency range of your instrument. I don't do much work with super fast risetime or high frequency signals so I am fine with the cheap 100 MHz probes (that really probably don't come up to that standard either.)
http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/380322063353?pt=LH_DefaultDomain_0&hash=item588cf623f9 (http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/380322063353?pt=LH_DefaultDomain_0&hash=item588cf623f9)
http://www.ebay.com/itm/250MHz-2000V-2KV-High-Voltage-Oscilloscope-Probes-P4250-/120693956323?pt=LH_DefaultDomain_0&hash=item1c19eb9ee3 (http://www.ebay.com/itm/250MHz-2000V-2KV-High-Voltage-Oscilloscope-Probes-P4250-/120693956323?pt=LH_DefaultDomain_0&hash=item1c19eb9ee3)
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It seems like you prefer that one specific seller out of Santa Clara CA. Any particular reason? Do you know that his products are US made, or at least not made in China?
You're probably right about the probes I linked to.... upon closer inspection, they do look EXACTLY the same....
One thing I did notice from the ones I linked to to the ones sold from your seller in Santa Clara - The ones you link to have a plastic cover around th BNC connector, and the ones I linked to have a cheap looking metal connector. With a close look at them, they look like the cheapest of cheap metal that looks almost like plastic! haha
Hmm.. $25 a piece though... unless I can get a deal on two for 30-40, I can only get one for right now. The HV probe will have to wait.
I don't know if it's the probes causing me the issues, but I'll just give you a quick rundown on what my scope is doing.
First of all, I know for a fact that I need to take it apart and clean the cam-actuated contacts for the V/div switch..... When I have it on with a probe hooked up and to the calibration loop, it's quite iffy. I have to fidget with the knob to get it to show a trace that matches what the probe book says it should be looking like. This sucks, because It's going to take me alllll day to do since I'm particularly anal about cleaning things like that, but I guess that's a good thing since I doubt I'll break anything.
I just need to go to Lowes and get some 100% pure Isopropyl Alcohol or Methanol. I doubt I'll find any camel hair brushes like the book recommends in "preventative maintenance" (hahaha - good ol' 1973 stuff....) I've seen that most people use paper strips soaked in alcohol to do the job nowadays.
The next issue is that, with the probe hooked up the same way, when I turn the 'position' knob, and the trace goes below the middle, it starts "zooming", and also when it goes above about the 2nd horizontal division line above the middle.
Channel 2 shows a horizontal trace, but has almost no vertical...
And both the probes I have, when I hook them up to my multimeter (one lead connected to the hook tip, one lead held in the connector) and let it hang, and wobble it around, the resistance reading bounces around between 8-9.3 Mohms. I don't think it's supposed to be doing that...... That's what makes me think I need to get some new probes before I can really figure out what issues my scope has. The upper part of the trace was going up and down the screen as I touched the ground clip a little, and same with the probe tip.
I have a cousin that lives in town that used to work as an electrical engineer and can calibrate this guy and maybe diagnose all these issues for me... when I can manage to get ahold of him. until then I'm just going to have to make due. For now I'll focus on cleaning up all the switches and getting the new probes..
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The Santa Clara guy sells the cheap ones too.... exact same as the ones I was looking at, same price, too.
http://www.ebay.com/itm/2-of-x1-x10-switchable-100MHZ-Oscilloscope-probes-4-HP-Tektronix-RIGOL-OWON-600V-/121170319361?pt=LH_DefaultDomain_0&hash=item1c36505801
Take a GOOOOD look at the picture that shows the tag on that one.............. see anything a bit off?!?!?? lol....
He did a photoshop job over the "200Mhz" to make "100Mhz" and same with the 6100 of "P6100"!!!
How can we trust ANY of these ebay sellers!!?? I mean, it seems like I'm gonna get ripped off somehow anyway!
What's your trick to being able to tell what ones are the good ones and what ones are the Chinese ones? lol
These look to be almost the exact same ones, but a pair and for a bit less.
http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/320570609224?pt=LH_DefaultDomain_0&hash=item4aa37f4e48
It also appears your Santa Clara seller has another store, selling the same stuff but for more.... same one you sent me the link to, but for $5 more.
http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/320822113669?pt=LH_DefaultDomain_0&hash=item4ab27cf585
This whole ordeal for finding the best deal on a GOOD pair of probes is a huge pain.
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Hey, he's not "my" Santa Clara dealer, I just found the probes on Ebay listings.
The only way to tell if they are any good or not is to get them and check, I guess. Looking at the "feedback" for the seller is also good, if the seller has 98 percent or better positive feedback they are probably honest enough.
I don't think you'll be able to find USA-made probes for cheap prices like those, everything is made in China these days and the quality is improving.
You can just take a cliplead from the scope's calibrator output and connect to a bit of wire stuck into the channel input jack, use the 1x scope attenuation setting and read a signal that way. You don't even have to worry about the ground connection as it is already connected inside the scope. This should give you a stable signal you can test with.
From your description I can't tell what is going on, maybe you can shoot a video showing the settings and the scope's behaviour, using the calibrator connection for a signal to each channel. Yes, you can connect the calibrator to both channels at the same time this way.
Don't use Methanol, it is very toxic! Absorbs through the skin, and by breathing vapors, and burns with an almost invisible flame, you could set something on fire and not even notice it. And you won't be able to get "100 percent" isopropyl unless you go to a chemical supply house. Just get a good grade of spray-on electro contact cleaner, like LPS brand from the car parts store, or "Jiffy Bath" from GC Electronics, sold in electronics supply stores. Even a Radio Shack might have a good "tuner cleaner" or electro contact cleaner. These cleaners will lubricate as well as clean the contacts. Read and follow the directions on the can. I would be very surprised if you had to use even a piece of paper, after cleaning with these products. You might get a bit of paper stuck in a switch contact....
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I read the negative reviews for that seller in Santa Clara and they were all in the last year, a lot in the last 6 months. I think I'm going to go with these:
http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/320570609224?pt=LH_DefaultDomain_0&hash=item4aa37f4e48
And in the "notes" section I'm going to nicely ask if they have any of the spring grounds, if they could toss a couple in with the probes. Hopefully they do. If not, oh well.
All they sell is mostly scopes and testers, and they have 100% feedback score, top rated seller, etc etc. so hopefully I'll be all good there.
I've been calling around and looking at the MSDS's for the cleaners, and all I can get here at auto parts stores, Grainger, etc is CRC Electrical Cleaner, which is more directed towards automotive plug connections.... Radioshack has Precision Electrical Cleaner all the way across town for 15 bucks, and theres another one closer thats going out of biz and 50% off everything, but all they have left is Deoxit ProGold which is a conditioner/enhancer, and the Deoxit PowerBooster is the cleaner.... so it looks like I'll be going across town...
I'm really not looking forward to the stress of pulling this scope apart and cleaning those contacts, but I know it has to be done, and I might as well do it before I take it over to my cousin and he can't give me a proper diag/calibration because of it.. LIFE...
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It appears that the "Modify" button has disappeared, so I can't just edit my last post.
Sorry for my own stupidity in not checking the materials that I already have to see if I had the info that I needed before going and asking a bunch of unnecessary questions and taking up people's valuable time to read/reply to them.
When I'm to a point where I know what I am doing, I will pay it forward and teach the next guy since you all are taking your time to teach me. That's only fair. Then when I am incorrect about something or leave out important info, you will only then have to take the time to add a little info.
Brian
[edit] - ahh I see now, apparently after a certain amount of time has passed, you are unable to edit your posts anymore... [end-edit]
- I am looing at probes to order, and from what I gather, the lower the model number, the higher the quality??
Here are my options for the standard 1x/10x probes:
---T5100 - http://www.ebay.com/itm/HQRP-100MHz-Oscilloscope-Probes-fits-Tektronix-HP-T5100-X1-X10-New-/221690519344?pt=LH_DefaultDomain_0&hash=item339dc8df30
---P6100 - http://www.ebay.com/itm/Two-x1-x10-100MHZ-Oscilloscope-clip-probes-HP-Tektronix-/290374567712?pt=LH_DefaultDomain_0&hash=item439bac4720
---TP6100 - http://www.ebay.com/itm/Two-Oscilloscope-Scope-analyzer-Clip-Probe-x1-x10-100MHz-Kit-For-Tektronix-HP/291177486377?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29170%26meid%3D8ad8e434a92c4ee9afad4dbc3106985a%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D220375454020&rt=nc
All of them are 6Mhz/100Mhz except for the P6100's, which are 4Mhz/100Mhz.
All of them are X1 = 150VDC peak; X10 = 300VDC peak, except for the TP6100 which are 300VDC/600VDC.
My scope's Max Input Voltage is (dc coupled) 250V(DC + peak AC) or 500V p-p ac at 1khz or less; (ac coupled) 500V (dc + peak ac) or 500V p-p ac at 1khz or less.
So, if I am correct here, If I want to be able to take advantage of the full ability of my scope with the 1X probe, I would want to choose the TP6100 probes?
Also, as for a HV probe -
http://www.ebay.com/itm/100MHz-High-Voltage-Oscilloscope-Clip-Probe-4000V-Alligator-Clip-Passive-P5100-/111586099163?pt=LH_DefaultDomain_0&hash=item19fb0cbfdb
http://www.ebay.com/itm/Tektronix-013-0290-02-Oscilloscope-Probe-Screw-On-Hook-Clip-Set-P5100-P5120-/321462078021?pt=LH_DefaultDomain_0&hash=item4ad8a20a45
Should I wait til I can afford that one and the spring loaded hook tip, or just get one along the lines of a $30 2kV probe with all the accessories?
I also noticed that none of those probes come with the spring point ground fitting. Is that just something more for HV applications?
Brian
heres a laugh..... a 1,000X 40kV probe....http://www.ebay.com/itm/1000X-P5104High-Voltage-40KV-40000V-20MHz-Oscilloscope-Passive-Probe-Clip-/291119549732?pt=LH_DefaultDomain_0&hash=item43c813cd24 :o
So the dirty secret about those sub $10.00 probes that Aidetek and others sell is that they use copper wire core coax. This means that the first 20ns to 50ns of any fast rising waveform is going to show a bunch of ringing that is reflections travelling up and down the probe cable. If you can live with that, then $7. a probe is cheap. The probes that Aidetek sell do work. The compensation box's adjust OK, and the measured bandwidth is a tad under the 100MHz they claim: about 80MHz. A colleague of mine and I bought a bunch of those probes, and hacked them up to make specialty probes.
If you want clean measurements of stuff faster than 1MHz or with rise and fall times faster than 50ns on a budget, then the 4900 series probes from ProbeMaster in San Diego CA run about $50. each depending on the options. If you buy from ProbeMaster get a couple of their high frequency ground adapters for $2.50 each. Or you can cruise eBay and buy used Tek or Agilent probes. Tek P2220's are decent 1x/10x switchable probes that really do meet their stated -3dB bandwidth of 200MHz, and have proper nichrome cable cores.
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Oh well, maybe I'll luck out with the ones I ordered. Next ones I get I'll go with the gold ProbeMasters.
Time to pull apart my scope and hit the switch contacts with deoxit D5....
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Oh well, maybe I'll luck out with the ones I ordered. Next ones I get I'll go with the gold ProbeMasters.
Time to pull apart my scope and hit the switch contacts with deoxit D5....
The probes from Aidetek are fine as long as you use them within their limitations.
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The probes from Aidetek are fine as long as you use them within their limitations.
I ordered these:
http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/320570609224?pt=LH_DefaultDomain_0&hash=item4aa37f4e48
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I ordered these:
http://www.ebay.com/itm/New-200MHz-Oscilloscope-Clip-Probes-Free-Accessory-Pack-/320570609224?pt=LH_DefaultDomain_0&hash=item4aa37f4e48
Hopefully they use nichrome coax cores. Please let me know how they perform once you get them.
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Hopefully they use nichrome coax cores. Please let me know how they perform once you get them.
Most certainly will do. If they aren't molded shut, I'll open them up and see what kind of coax core they have.
The reason I went with those is because they've sold hundreds of them and have a 100% positive feedback rating, and are a top rated seller as well. I have my fingers crossed they use nichrome........
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Do the BNC patch cables that you use have nichrome coax cores? Cuz I noticed that most BNC patch cables are RG58 or RG59. I got some BNC/RG6 compression connectors at RadioShack, and I have several different kinds of RG6 - the best being XFT, and also Eagle Aspen 3.0Ghz RG6. All of it is 18AWG copper core, though.
Also, I took my scope apart and took the preamp board off. I detailed everything with IPA and cleaned all the switch contacts and finger contacts with deoxit D5 and then IPA. I made sure I got the 91% IPA, which is pretty much the best I could find. I'm not taking any of the other boards off unless I have to due to desoldering, but there is absolutely no visible damage to anything on the preamp board, so I switched the attenuators around from CH1 to CH2 and vice verse, so if CH2 works and CH1 doesn't, I know what part is broken. Otherwise, I'm going to end up going thru all the tests/calibration steps one by one until I figure it out... since its $365 to calibrate professionally, and the service centers stopped doing repairs on the 465 in 1994... If it isn't the attenuators and is something else, I will hook it up with a direct line to the calibrator and make a vid showing what it's doing. Hopefully I've fixed the V/div issue at least, though.
One more thing, my unit has attenuators for 100X - so I guess it would automatically adjust the readouts for a 100X probe. Unless that means something completely different from what I am thinking.
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Most certainly will do. If they aren't molded shut, I'll open them up and see what kind of coax core they have.
The reason I went with those is because they've sold hundreds of them and have a 100% positive feedback rating, and are a top rated seller as well. I have my fingers crossed they use nichrome........
I bought some "200MHz" probes that were about the same price, but the appearance is different. They were very so-so. Hopefully what you've bought will be better.
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Do the BNC patch cables that you use have nichrome coax cores? Cuz I noticed that most BNC patch cables are RG58 or RG59. I got some BNC/RG6 compression connectors at RadioShack, and I have several different kinds of RG6 - the best being XFT, and also Eagle Aspen 3.0Ghz RG6. All of it is 18AWG copper core, though.
Also, I took my scope apart and took the preamp board off. I detailed everything with IPA and cleaned all the switch contacts and finger contacts with deoxit D5 and then IPA. I made sure I got the 91% IPA, which is pretty much the best I could find. I'm not taking any of the other boards off unless I have to due to desoldering, but there is absolutely no visible damage to anything on the preamp board, so I switched the attenuators around from CH1 to CH2 and vice verse, so if CH2 works and CH1 doesn't, I know what part is broken. Otherwise, I'm going to end up going thru all the tests/calibration steps one by one until I figure it out... since its $365 to calibrate professionally, and the service centers stopped doing repairs on the 465 in 1994... If it isn't the attenuators and is something else, I will hook it up with a direct line to the calibrator and make a vid showing what it's doing. Hopefully I've fixed the V/div issue at least, though.
One more thing, my unit has attenuators for 100X - so I guess it would automatically adjust the readouts for a 100X probe. Unless that means something completely different from what I am thinking.
You only want nichrome in the scope probes. In the coax you want low loss copper. The flattest response probe that you can get or make is called a transmission line probe: The coax cable is matched by its characteristic impedance at the input to the scope: typically 50 Ohms. $5000. and up scopes typically have a 50 Ohm / 1 MOhm input impedance control. For the rest of us poor slobs, you can buy a male / female 50 Ohm through termination. The coax cable would then load your circuit with 50 Ohms, which is a bit much for most circuits. So, what Tek and Keysight offer are those kinds of probes with a series resistor. A 450 Ohm series resistor makes a 10:1 voltage divider with the impedance of the cable and the circuit sees 500 Ohms instead of 50 Ohms. The Tek probe is a P6150. Keysight offers a probe with a 950 Ohm series resistor, that makes 1000 Ohms to the circuit and 20:1 attenuation. It's a 1980's design. I would have to look up the part number. You can make a probe tip yourself or scrounge around eBay for one of the probes I mentioned. Usually people want way too much money, but they pop up now and again for $100.-$150.
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So I have been doing a bit of research on what type of Coax wire to use for home-made probes.
This is the info I found, and the material I chose. I want to see what you think about these materials.
https://en.wikipedia.org/wiki/Coaxial_cable
I chose RG316/U as the best possible candidate.
This type of cable is used in Nuclear Instrumentation Electronics.
Here is a link to an ebay item that has more info on the specs of the cable.
http://www.ebay.com/itm/10-ft-RG316-U-RG316-Equiv-Excellent-Quality-Coax-Cable-USA-SELLER-FREE-SHIPPING-/251237252458?pt=LH_DefaultDomain_0&hash=item3a7ee83d6a
http://www.ebay.com/itm/RG-316-MIL-C-17-Coax-Cable-50-Feet-/221625146764?pt=LH_DefaultDomain_0&hash=item3399e35d8c
I had to look up the "core material" - turns out SPCCS is Silver Plated Copper Coated Steel.
Here is some other cable with a much, much higher attenuation. It is "rg8X"
http://www.ebay.com/itm/USA-MADE-RG8X-95-SHEILDED-HAND-SOLDERED-50FT-CB-HAM-COAX-RADIO-CABLE-PL259-/170974652520?pt=LH_DefaultDomain_0&hash=item27cee22868
I wasn't able to figure out or find the exact kind of wire that is used for probes, so the only thing I can think of to find out would be to call Tek or another company that manufactures them and ask, or see if I could get one of the smaller probe manufacturers to tell me, which I doubt they would since there is only one reason why I would want to know - to get some and make my own!!
So what are your thoughts on this? I know that just buying some high quality probes is the best way to go, but what I am thinking about here is the possibility of making my own probes that are similar in performance to the extremely expensive probes that are on the market. It'll be easy enough to make my own spring-loaded tips out of other types of hook tips that are out there, and easy enough to make my own connector base units for the resistors, caps, and adjuster. If I don't feel like doing it by hand, I could just get someone with a small CNC machine to make them for me. If this works out, and the performance is good, I'm sure this could turn into a new way for us who can't afford a $500+ dollar probe to make some that are "good enough".
Brian
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Uhh..... no.
See the attachments below.
And also this document:
http://www.ece.vt.edu/cel/docs/TekProbeCircuits.pdf
If you insist on making your own, you might as well use the much cheaper RG174/U, I guarantee you will not be able to detect the difference between that and RG316/U on your oscilloscope, except that the 174 will be more flexible and easier to handle.
However... whatever floats your boat.
If I were you, though... I'd concentrate my efforts on troubleshooting and repairing and restoring the oscilloscope, using the probes you have already ordered to learn how to use it properly on various projects, and start saving money to buy your _next_ oscilloscope, or a more modern Function Generator with more waveform output choices. A good dual tracking powersupply is also an important investment for your electronics workbench.
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Yeah, true.
I tend to get a little ahead of myself sometimes.
Thanks for the info. I'm still working on cleaning this thing up and running some deoxit D5 into the pots and switches to clean out the contacts. Most of them caused the trace to "scratch around" a bit so I might as well do it while I have it open, and then I'm going to make sure I clean off any excess cleaner, hard to reach dust, etc with this CRC QD electronic cleaner that I picked up. Hopefully all works out well. Then I can focus on learning how to use it....
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well, now my scope has a new problem.
I think I may have managed to resolve most of the "noise" issues with the pots and switches, but now I've awoken a whole new problem.
GREAT.
I wish I could just go buy a brand new scope... I get the feeling I may never get this one working properly, especially since I don't have the testing equipment that the manual states is needed, and have absolutely no experience when it comes to diagnosing or fixing this complex of an electronic device.
https://www.youtube.com/watch?v=uOlpdG6qwpQ (https://www.youtube.com/watch?v=uOlpdG6qwpQ)
I really hope someone has an idea about what is wrong with this thing. At this point I wish I never would have even opened it up... or even got it for that matter.... :(
Thanks for the help thus far, and any help you are able to provide me in solving these issues....
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well, now my scope has a new problem.
I think I may have managed to resolve most of the "noise" issues with the pots and switches, but now I've awoken a whole new problem.
GREAT.
I wish I could just go buy a brand new scope... I get the feeling I may never get this one working properly, especially since I don't have the testing equipment that the manual states is needed, and have absolutely no experience when it comes to diagnosing or fixing this complex of an electronic device.
https://www.youtube.com/watch?v=uOlpdG6qwpQ (https://www.youtube.com/watch?v=uOlpdG6qwpQ)
I really hope someone has an idea about what is wrong with this thing. At this point I wish I never would have even opened it up... or even got it for that matter.... :(
Thanks for the help thus far, and any help you are able to provide me in solving these issues....
Don't get discouraged yet. When you can't get a beam at all, even with the Beam Finder, that's when to get discouraged!
In the video it looks to me like you have the Timebase knobs set to "x-y" mode (all the way CCW.) Is that right?
Please set the controls up like in the images below, and post a photo or new video of the traces you get.
Connect the CH 1 input to the calibrator. Just the center pin of the input jack to the calibrator bar, don't worry about a ground connection for now. I wouldn't even use a probe for this, just a cliplead from the cal bar to a wire stuck into the center pin of the CH1 input jack.
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@Brian: Did you get the full Service Manual? There is a Troubleshooting guide in there. I've found that these guides are very good and will help you track down the problem to the board or even the component level.
http://elektrotanya.com/tektronix_465_oscilloscope_full_sm.pdf/download.html (http://elektrotanya.com/tektronix_465_oscilloscope_full_sm.pdf/download.html)
A good DMM is probably all you'll really need to check it out. The very first things to check will be the power supply voltages, according to the instructions in the SM.
I'm surprised that the thing has "deteriorated" since you brought it home. Are you sure you didn't knock something loose, or leave a screwdriver inside, or something like that?
:-\
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Well I hope the scope is on X-Y but I am highly suspicious. You have a dot in the center and you can see two pale filament curves going towards the bottom of the screen. I am suspecting that perhaps the the scope is not on X-Y and the horizontal timebase is not working. The explanation for the two pale filament curves is that normally the beam is pulled off the screen below the bottom of the display during the horizontal flyback. If this is the case, as the timebase knob is switched to lower speeds you might see the two pale filament curves start to flicker.
If we assume that I am correct and there is no timebase sweep, and you see varying flickering speeds when you change the timebase, then that would be telling you that the horizontal timebase oscillator is most likely still working. I think there is a good chance that it could then just be a mechanical contact problem somewhere inside the scope. The next step would be to try whacking the side of the scope just like an old TV. Do this very lightly at first and do not do it hard and do it at your own risk. Try a light whack for different timebase settings. If after a whack you see the beam do a normal horizontal deflection, even it it is just for a fraction of a second, then stop whacking and you are 90% of the way towards the solution.
The whacking made a failed electrical contact between the horizontal timebase oscillator and the horizontal deflection amplifier connect for a short time. So then the next step would be to open up the scope and clean all of the contacts associated with the rotary timebase selector switch with Q-tips and WD40.
Here is a "big secret:" Just put a very tiny tiny amount of WD40 on each contact point, then cover the opened up scope with something to prevent dust coming in and then just wait about two days. The WD40 will do it's magic over the two days.
I learned this from this guy's channel: https://www.youtube.com/user/AllAmericanFiveRadio (https://www.youtube.com/user/AllAmericanFiveRadio)
I have watched clips were he does just that. Takes a tiny tiny amount of WD40, applies it to the bad contacts, waits two days, and then everything works fine. When you do this instead of spraying you do not contaminate the inside of the scope with excess contact cleaner.
CAREFUL if you take my advice and whack the side of your scope. Perhaps opening up the scope and just tapping on the rotary switch for the timebase selector with a piece of wood would be better. All of my suggestions and advice are at your own risk.
MileHigh
P.S.: Whenever you see a static dot on your scope display you should immediately turn the intensity way way down to protect the screen phosphor.
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Please read the SM from the link above about cleaning the switches and other contacts. Sorry, but the SM specifically warns against things like Q-tips (they leave fibers behind which can cause intermittent contacts) and petroleum based solutions (they degrade certain circuit board materials used in the scope.)
I do agree with the gentle whacking, and the rest of the stuff in your post. The behavior of the scope has changed since Brian has cleaned it, so it's almost certain that he's managed to knock something loose, disconnected or broken a wire, or fouled a switch contact or something like that.
The first thing, though, is to get it out of X-Y mode if that's where it is, and see if any kind of trace makes sense. The fact that the display has the really bright spot on it is a little disconcerting, I don't know if the Intensity control is fouled or what. I think at this point that there definitely is a problem inside, but also that the controls aren't set properly to produce an interpretable trace.
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No Q-tips makes sense. In that guy's channel that I linked to, he may have just put a tiny tiny drop of WD40 on the dirty contacts with the tip of a needle or a jeweler's screwdriver, and then he just touches the contact point. When I saw that I was somewhat surprised and embarrassed because I have cleaned the pots in old 1970s amplifiers with very messy "brute force spraying." :D
That's a great segue into some classic advice: You want a good sound system for your main computer? In the springtime go out to some garage sales and get a nice 1970s integrated amplifier or stereo receiver for $30 or less. Clean the volume control knob and the input selector switch. Get a decent set of stereo speakers and then you will be in computer sound system heaven. It's getting pretty late now, so old amplifiers and receivers are probably getting scarce!
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AHA!! we have liftoff!! still some kinks to work out it seems, but progress!
I don't know if it was just be being dumb and not having the proper settings, but the only real difference between the settings before and the settings now is the coupling is set to AC instead of DC, and the input is also set to AC. oh, and the time/div to 1ms instead of X-Y... which must have been the major issue I suppose??
I did change the coupling to AC and input to AC before when I was trying to get it working, but not the time/div. If not, maybe the gremlins inside the case fixed it while I was attempting to fix this 1000W amp unit.
One other thing that is different, which I mention in the vid, is where exactly I had the power plugged into. before I had it plugged into an extension cord that also had a lamp plugged into it. Now I have it plugged directly into the wall outlet, but it's the same outlet that I had the ext cord plugged into.
I'm going to go with the story that the tube gremlins fixed it.... so I don't feel so stupid! :)
There are still a few kinks that those gremlins need to wrench on, though, such as the brightness of my vertical lines, the bad illumination bulb at the bottom of the CRT, and the pot noise.... haha
https://www.youtube.com/watch?v=M9slPe8A3lw
Thanks !! :) :) :) :)
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The video shows up as "private" so you have to put us on the list specifically by username. Or you could change it to "unlisted", then anyone with the URL can see it but it still won't appear on searches.
There is a difference between "Trigger coupling" and "input coupling". The input coupling is the one under the channel vertical scale knob. The Trigger coupling is over on the right in the trigger/timebase section. Also the trigger source should "not" be set to "line".
There is still something wrong because even the X-Y display should not look like that; with no inputs to the channels it should produce a single dot, that can be finely focussed to a point, without tails or bright blooming.
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Ah OK, now the video link shows as "being processed".
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TK-
Yes I do have the full, original service manual, including the manuals for the probes. I was thinking that I was going to need a working scope and function gen to properly test this guy.... but I probably will in order to properly calibrate it, right?
I really didn't think I had messed anything up... I was EXTREMELY careful when cleaning it, and made sure I read the part of the manual on preventative maintenance to make sure I didn't use any products that would harm it. I used IPA and some camel hair artist paintbrushes, and Deoxit D5 for the contacts and pots, then cleaned up any excess Deoxit with IPA. I went thru it several times cleaning and inspecting, and saw nothing that was broken or damaged at all. In fact, it seemed to be in near-mint condition inside to begin with other than a little dust. It doesn't have a filter on the fan, and hasn't for who knows how long now, so I'm surprised it didn't have more fuzz inside of it.. I'll need to get some material to make a filter, or just buy the ones someone is selling on ebay. $15 for 100 tek brand replacement filters... but it looks like a pretty common filter material.
There still is quite a bit of noise occurring from somewhere, it seems to mainly be coming from the A trig level/slope knobs, the A trig holdoff, and the time/div contacts. I didn't take that board off and clean any of those. Since those controls are right up against the faceplate, I might see if there is enough room for me to get the tip of the Deoxit straw to the shaft if I just take the faceplate off. But if I have to take the board off to clean it, I'll just have to do it I guess. The only board I took off was the vertical preamp/vertical sweep assembly. all those seem to work perfectly now, so I must have done it right.
Milehigh -
Yes, I had it in X-Y.... ::) Goes to show you how very little I know about using a scope.....
It's producing a readable trace now, but it still seems to have a some minor issues as you'll see in the vid once it's done uploading....
That is def some good info, though. Good to know for future restoration and cleaning projects!
I'll have to go garage sale/yard sale hunting once spring comes around and see what kind of goodies I can find! I should have some funds to play with by then.
Maybe I'll even run across some stuff that you and TK might be interested in that I can pass on. never know...
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Ah OK, now the video link shows as "being processed".
Ahh I just noticed that youtube froze up on me. I'm having to do it all over again. Hopefully it actually works this time....
I'm going to make sure that it works and then I will edit this and put the link in it.
https://www.youtube.com/watch?v=v9PxTExuJjU
Someone was leaching my bandwidth and somehow affecting my upstream in the process.... stupid Xfinity and their unprotected wifi access point for "other Comcast customers". Bout to disable their router in the combo device and hook it to my other one. It's finally done though.
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Brian:
The scope is working just fine. I am assuming when you change the horizontal timebase it also woks fine.
The fact that you can barely see the vertical lines is a very good thing. I am not going to bother explaining why, you will figure it out as you learn. Your triggering level function is working just fine and doing exactly what it is supposed to do.
Do not worry about the blown light bulb to illuminate the scope display. If it is difficult to get at to replace it would be a very foolish move on your part to replace it because you will incur more risk of accidentally damaging the scope. You absolutely do not need that light bulb replaced and chances are you will almost never use the display illumination function.
MileHigh
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Brian:
The scope is working just fine. I am assuming when you change the horizontal timebase it also woks fine.
The fact that you can barely see the vertical lines is a very good thing. I am not going to bother explaining why, you will figure it out as you learn.
Do not worry about the blown light bulb to illuminate the scope display. If it is difficult to get at to replace it would be a very foolish move on your past to replace it because you will incur more risk of accidentally damaging the scope. You absolutely do not need that light bulb replaced and chances are you will almost never use the display illumination function.
MileHigh
That's what I was thinking, too. It doesn't seem like any of the illumination lights are really actually necessary.
One thing I did notice after the vid, when I started changing the horizontal timebase to anything but 1ms It started showing a bunch of "noise" on the sides. It also had it intermittently on 1ms, but nowhere near as bad as any other setting. Probably just needs a good cleaning, such as the WD40 trick, but just in case, I'll make a little vid to show you what I'm talking about once I'm done eating. It only seemed to do it after it was warmed up all the way, though. If there is really such a thing....
It only really started happening after it was on for about 5 minutes, though.
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OK, that looks great! No there is nothing wrong with the "vertical lines", you are seeing a good fast risetime from your calibrator that's all. Now change the timebase to a faster value so you get just three or so cycles on the screen. Then you should be able to see the rising and falling edges of the squarewave pulse from the calibrator.
(Just leave everything else like you had it for now. The Delayed Timebase and all that is an "advanced functionality" so let's just get the basic controls down first.)
Don't push the intensity so far up that the bright places bloom out, that's not necessary. In general I like to run mine at the dimmest value that gives me a good picture. This will also help you get a sharp focus on the traces. These functions (intensity and focus) are generally High Voltage functions of the CRT display circuit.
I love those orange graticule illuminators! My old RM503 has a nice orange graticule and a blue persistent "photo-ready" phosphor so it really looks cool. Be careful about replacing with LEDs and resistors, sometimes this doesn't work because of the way Tek drives those lights from transistors. I'd recommend using the right bulbs here, they are generally available still.
Now let's try the second channel, with the same vertical amp settings as on the CH1. Just put the Vert Mode switch over to CH2, the Trigger Source to CH2, connect the calibrator to that channel input and let's see the trace from CH2.
Then if you got a good trace on CH2 you can try both traces at once, by patching the calibrator output to both channel inputs. Select "Alt" in the Vert Mode buttons for the dual trace display. Trigger on either CH1 or CH2 (if you got a good trace on CH2 before.)
Something to watch while you're eating....
;)
http://www.youtube.com/watch?v=q55-CTCd2k4
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https://www.youtube.com/watch?v=C8WUWgIVG0A
says it will be done uploading in about 6 minutes.
Hopefully it's just some noise off the input. It wasn't there before, though.
AHHH! Now it's all just getting worse!! I have a curved line on the screen when there is no input into it, and that noise wont go away. I tried different clip leads, different wire into the input jack, and even a probe. :( I hate my life sometimes....
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Hmmm.... yes that's weird all right. Can you turn the CH2 input coupling to "ground" and see if that makes any difference? Also make sure you don't have any of the Delayed Timebase functions active. (Crank the Delay Time Postion knob fully CCW, make sure you have "A" selected on Horiz. Display buttons, and both A and B knobs on the Time/Div knob in the same position, with the red Var knob all the way CW and in the detent if there is one. ) I don't really think this will make much difference but let's check anyhow just to be sure.
Try changing the Trigger Source from Norm to CH1 and see if that affects the weirdness.
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https://www.youtube.com/watch?v=C8WUWgIVG0A (https://www.youtube.com/watch?v=C8WUWgIVG0A)
says it will be done uploading in about 6 minutes.
Hopefully it's just some noise off the input. It wasn't there before, though.
AHHH! Now it's all just getting worse!! I have a curved line on the screen when there is no input into it, and that noise wont go away. I tried different clip leads, different wire into the input jack, and even a probe. :( I hate my life sometimes....
No, that's good! That means it's probably a heat-related problem, and those can be tracked down with an approved "cold spray" applied to suspected components like transistors or capacitors that might be failing. And the first thing to suspect is the power supply voltages. There is a good troubleshooting flowchart in the SM for checking the Power Supplies. With a little intelligent and careful guessing, and poking around with the approved cold spray, you may be able to find the tantalum capacitor that's causing the difficulty.... (just a guess at this point...)
I'd still like to know what the CH2 trace looks like, maybe after shutting down and letting it cool off for a while.
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Here's a link that has some good info and a paragraph or two specifically about the 465 and its tantalum caps:
http://www.repairfaq.org/sam/tshoot.htm#tshtek
And I +think+ this Cold Spray is probably OK to use, it's Freon 134 which didn't exist when the scope was made:
http://www.mgchemicals.com/products/dusters-cold-sprays/cold-sprays/super-cold-134-403a/
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It certainly is strange. It possible it's related to the flyback blanking interval again but that's just a guess. If the trigger level is set just at the upper or lower threshold of the square wave that might cause some horizontal jitter if you are right at the edge. However, that can't explain the loopy "noise" waveform. You should try changing the trigger level just the same and then leave it at around zero volts.
Something is loopy for sure. For me the next step would be to exercise every single function of the scope for the internal square wave and for an external signal to get a full sense of the scope's health. However I realize that would be next to impossible for you because you are a newbie.
The "noise" waveform is exponential in nature. That's not a surprise in itself but it might be a clue.
TK mentioned thermal issues also. The advice from me would be to chill the scope down just a bit (you don't want condensation) and then run it and see if the scope works fine for 10 minutes before the problem starts happening. Then like TK said you may have a single failed semiconductor component. Finding that is not too difficult if you know what you are doing. I would not advise you to do this yourself.
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https://www.youtube.com/watch?v=C8WUWgIVG0A
says it will be done uploading in about 6 minutes.
Hopefully it's just some noise off the input. It wasn't there before, though.
AHHH! Now it's all just getting worse!! I have a curved line on the screen when there is no input into it, and that noise wont go away. I tried different clip leads, different wire into the input jack, and even a probe. :( I hate my life sometimes....
Your brightness is set way too high. Youare going to burn the screen with settings like that. Put the same signal on channel B and see what you see.
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Heck, I think Brian can handle it. The tantalum caps are easy to recognize on the boards, and simple to test by unsoldering one leg and testing for resistance with the DMM, or a capacitance meter that he could probably borrow if he doesn't want to buy one. Check the PS voltages in the low voltage supplies at the test points indicated on the schematic with a DMM, following the troubleshooting chart in the SM for the power supplies. I'll bet a cheezburger that there is an off-voltage supply and that the cause is a bad tantalum or foil electrolytic capacitor or two.
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I have a few things I have to get done today, but hopefully later this evening I'll be able to do some more troubleshooting, test channel 2, and run thru the tests you both suggested while recording it all on vid. it would be nice if I had an actual vid cam and tripod for this but I'll see if I can borrow an extra set of hands for a few min so I can get it done quicker.
You sure using a refrigerant chill spray in something like this won't cause any additional problems?? what am I saying, of course you are, you must be.. you know a whole lot more about this than I do.....
I was thinking about possibly opening it back up and finishing the cleaning by removing the trigger boards so I can access the time/div drum and finger contacts properly, and clean it all up really good with IPA.... just in case there is some sort of fuzz in there crossing some contacts, and so we can get an entirely accurate picture of what could be wrong while knowing it isn't a switch contact or dust issue. then I could leave the case off for the testing to get a visual with power on, and also check the voltages. do you think this is worth doing first, or should I just leave it as-is and continue troubleshooting?
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Your brightness is set way too high. Youare going to burn the screen with settings like that. Put the same signal on channel B and see what you see.
that is an effect of the camera. the brightness was only up just high enough to where the vertical traces are slightly visible. the illumination was also down all the way. I don't know why the camera does that. maybe I have it on low light setting or something.
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I'd like to see a bit more data, like the second channel trace, before you start taking it apart. If you take the case off that might give you a longer test time before it starts glitching. Also, turn down the intensity! The trace should not "bloom" under normal conditions, it should just make a nice readable line without illuminating more of the phosphor than needed for visibility. Don't worry at all about not seeing the rising and falling edges from the Calibrator, that is normal at this horizontal resolution and indicates that the calibrator circuit is giving you nice fast rise and fall times, a good thing.
Instead of using the scope's calibrator as a signal source, you could also try connecting the GenRad oscillator to get a sine waveform instead of the square wave. For low frequency testing you don't really need to worry about fancy connectors or precise impedance matching, just use clipleads to connect the GenRad's ground to the scope's BNC grounds and another cliplead to connect the center pin of the GenRad connectors to the center pin of the scope's BNC channel inputs. Set the GenRad to the same frequency as your calibrator output. The sine wave will not have "invisible" portions like the square wave from the calibrator does. Start with the output of the GenRad set to the lowest possible value, then gradually turn it up until you have an acceptable trace amplitude on the scope.
When you do open it up and start prowling around in there, I would suggest that the very first thing you do is to check the power supply voltages, using a DMM and the information in the SM. You have a handful of low-voltage DC supplies to check, starting with the +55V supply. Since you have a good beam and at least acceptable traces until it starts glitching, I wouldn't even worry about the HV supply at this point. But off-voltage LV supplies can cause all kinds of weird problems, and since these use old and maybe flaky capacitors, and the problem is heat- or at least on-time related, that's where to start looking.
The LV power supply test points and voltage ranges are on section 6-8 in the SM. You'll have to look at the board drawings to find the locations of the numbered test points. Don't worry about testing the HV supply. And don't try adjusting anything yet! Just let me know what the voltages are at the test points. Be sure to set the scope's controls as required for the PS testing. The voltages are referenced to chassis ground, so use a nice sturdy cliplead to "permanently" connect the DMM's Minus input to the chassis. Then carefully probe the TPs with the DMM's pointy red lead. Be very careful because obviously you don't want to short anything out or hit a HV point by mistake. But this is actually really an easy testing to do once you have located the correct testpoints on the boards.
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that is an effect of the camera. the brightness was only up just high enough to where the vertical traces are slightly visible. the illumination was also down all the way. I don't know why the camera does that. maybe I have it on low light setting or something.
Turn the intensity down! The vertical parts of the traces from the calibrator on the settings you are using are _supposed_ to be nearly or even completely invisible. The important part is the horizontal parts of the traces and these should not "bloom" excessively beyond the trace itself.
Of course if you really _need_ to see the rise and fall edges for some reason you turn up the intensity. But normally you would run at a lower brightness level.
Note that in the "normal" pic below the horizontal portions do not "bloom".
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that is an effect of the camera. the brightness was only up just high enough to where the vertical traces are slightly visible. the illumination was also down all the way. I don't know why the camera does that. maybe I have it on low light setting or something.
The traces were blooming heavily. If you don't turn it down, you are going to burn the screen.
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Well, I am going to repeat my cautionary note again. I get the impression that Brian has no electronics experience at all and finding bad components and changing them inside an oscilloscope is not a trivial matter even if you have the service manual.
As an example: Brian, if you switched off the power to the scope but left it plugged into the wall socket, did you know that if you touched a component with a regular soldering iron things could "blow up?" If you didn't know that then that shows you should be careful.
Here is a way of looking at it: From what I can see from your clips the problem is annoying but tolerable. The scope is still working and showing you waveforms. The suggestion is to just use it like that for now. In six months if you truly are interested in this stuff and are learning the whole time, then perhaps try to fix it. However, there is a chance that in six months you will have moved on and dropped the whole thing. Then fixing the scope becomes a moot point because you will not be using it.
MileHigh
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Oh ye of little faith.
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In my "tear apart tinkerer" life there were a few times where I got in over my head an I was unable to put back together what I tore apart. When it comes to intermittent problems, those can be a real serious pain to troubleshoot and fix and sometimes it can take weeks. And that's with a bench full of equipment at your disposal. I am not saying this problem is truly intermittent but it has some traits like that. If it is truly thermal, then finding the bad component with a heat gun and freeze spray is doable, if you really know what you are doing. Brian may not have even known that heat guns and freeze spray existed for this purpose. Then you throw in the dangers of high voltage, and how ideally you would have a second scope to fix the first scope, etc.
Perhaps Brian will get lucky and cleaning the contacts will do the trick!
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Well, I am going to repeat my cautionary note again. I get the impression that Brian has no electronics experience at all and finding bad components and changing them inside an oscilloscope is not a trivial matter even if you have the service manual.
As an example: Brian, if you switched off the power to the scope but left it plugged into the wall socket, did you know that if you touched a component with a regular soldering iron things could "blow up?" If you didn't know that then that shows you should be careful.
Here is a way of looking at it: From what I can see from your clips the problem is annoying but tolerable. The scope is still working and showing you waveforms. The suggestion is to just use it like that for now. In six months if you truly are interested in this stuff and are learning the whole time, then perhaps try to fix it. However, there is a chance that in six months you will have moved on and dropped the whole thing. Then fixing the scope becomes a moot point because you will not be using it.
MileHigh
Yes, I know very well the proper way to use and work on electronics. I'm not a complete moron. I can solder perfectly well, know how to desolder.
I'm not trying to be rude here, but I'm not some average dummy. I may not know anything about oscilloscopes, and I may be a beginner in learning about how more complex circuits function, but I've known how to solder and how to fix things for a long time now.
A little background on me: When I was a little kid, my favorite thing to do was take things apart, learn how they work, and then put them back together. I never cared about action figures or pointless stuff like that. I started doing construction at 13 and excelled at it, started fixing cars at 15, and excelled at that.
I've wired up multiple houses, mapped out the circuits in houses built in the early 1900's that had knob and tube wiring, rewired houses, fixed circuits, etc.
It was only recently that I got back into smaller electronics though. I'm a little older now and don't learn as quick as I used to, and it's not as easy for me to figure things out like I used to, but I still can.
So what I am saying here is I'm not your average numbnuts and I don't like to be treated as such.
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Milehigh,
Sorry for lashing out at you. I shouldn't have. I just really hate being spoken to like I'm a dimwit, and that's how I felt after reading your comment about knowing to have devices unplugged before doing any work inside of them. I know it's probably a bit too early into my electronics learning experience to be worrying about learning how to use a scope and everything, but I love "toys" (especially electronic equipment that give me a better idea of how something is functioning....), and this one was too cheap to pass up. If I had to spend a few hundred to get one, you bet I would have waited until I really needed one.
Even so, I appreciate the help with all this and for you guys putting up with me not knowing more than just the very basics of electronics...
The major thing that I need to start doing is taking the time to read the manual, and even the manuals for other things I have like my Fluke DMM and other DMM's. I'm sure there are functions on them that I am missing out on, plus I need to learn how to calibrate them myself. I guess it's just that manly instinct to just " figure things out as I go " that I need to get over, especially when it comes to this type of equipment. I would have easily figured out that having it on the X-Y setting was my issue before if I would have bothered to open the manual to the 'Obtaining Basic Displays' section.
Anyway.... back on track...
My internet was down earlier for a while I guess due to the heavy snow and crazy wind, so I decided I would pull it open again and inspect, again, this time focusing on the dipped caps....
I found one on the vertical preamp that has a hairline crack in it, and one on the IC board in the Power supply +5V rail.
The one on the +5V rail is number C1559. It's split apart by one of the leads. It looks to have been caused by heat, from the component itself though since there are no heat marks around it, the fan works, and everything else in the area is in great shape.
The one on the vertical preamp board only has a hairline crack on the top of it. I thought it was just the paint but i ran my fingernail over it and there is definitely a crack.
It is part number C161 on board A3. It is also part of a +5V section of the board, interestingly enough. both caps go to ground.
Could this possibly be part of a bigger issue, since they are both on +5V?
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00162_zpszrmhxqju.jpg
(also notice the axial cap to the right of the bad tantalum cap - it's outer plastic is peeling off. Appears to just be cosmetic, unless you think it happened because it's going bad.)
Brian
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Brian:
All is well and fine. The soldering iron issue happened with someone well known around here about a year ago and he is a guy that also loves to take stuff apart. My language may not always be the most politically correct but I was not trying to prejudge you. You seem to be making progress so I hope that you fix it and then you are off to the races. Just be careful of the high voltage. TK is the expert there and might have some sound advice for you about that.
MileHigh
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Brian:
All is well and fine. The soldering iron issue happened with someone well known around here about a year ago and he is a guy that also loves to take stuff apart. My language may not always be the most politically correct but I was not trying to prejudge you. You seem to be making progress so I hope that you fix it and then you are off to the races. Just be careful of the high voltage. TK is the expert there and might have some sound advice for you about that.
MileHigh
That's unfortunate that someone didn't know not to stick an induction stick into a hot electronic device.... I wonder how big of a "poof" or "POP" it made. Nowadays I don't take stuff apart that I intend to keep in one piece unless it's broken.
The internet and text messages aren't the greatest modes of comm since there is the full lack of tone and emotion, so a lot of times things don't come out the way one intends them to. That happens a lot to me especially it seems. Sometimes when I go back and re-read something a bit later I realize that It reads completely different from the way I intended it to.
Fortunately, going into this I knew enough about electricity to have some respect for it. Especially high voltage. Especially DC HV, since at least AC will throw you away from it, instead of getting stuck to it. I at least know how to read schematics and understand when caps will need to be discharged before handling.
I posted a pic in the above post of the bad +5V PSU cap. The other one isn't worth bothering to take a pic of, since you wont be able to see the crack in it anyway.... maybe if I rubbed it with some powdered pencil graphite it would be noticeable enough to capture in a pic....
Brian
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Especially DC HV, since at least AC will throw you away from it, instead of getting stuck to it.
Brian
I am no expert but this is not correct from what I was taught while working on 3 phase 240 volts machinery. I was taught that you never grab anything...you use the back of your hand so in case you get zapped, and your hand closes involuntarily, you are not clinging to a hv source. Now, maybe this is only true for 3 phase circuits but...I don't think so. This saved my life once when working on some equipment (before lock-outs were invented) with the breaker off and, a note saying to leave it off. Well, someone was trying to figure out why their machine was not working and...yes...turned it on. I did get bit but, I was careful not to be in a position to have my hand close around the wire. I was also taught to use one hand only, that way the charge does not go across your heart.
Off-topic I suppose. Sorry.
Don't worry...your scope was made with quality components and meant to last. It could easily be as simple as one of those caps. You will get it figured out and then you will feel very proud for doing so. I know that I would.
Bill
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I found one on the vertical preamp that has a hairline crack in it, and one on the IC board in the Power supply +5V rail.
The one on the +5V rail is number C1559. It's split apart by one of the leads. It looks to have been caused by heat, from the component itself though since there are no heat marks around it, the fan works, and everything else in the area is in great shape.
The one on the vertical preamp board only has a hairline crack on the top of it. I thought it was just the paint but i ran my fingernail over it and there is definitely a crack.
It is part number C161 on board A3. It is also part of a +5V section of the board, interestingly enough. both caps go to ground.
Could this possibly be part of a bigger issue, since they are both on +5V?
Yes, this could be a problem. The pic you posted... yes, that cap sure does have a crack in it. This could be bad or not, but I'd replace it anyhow. That's C1559, a 33uF 10V tantalum, and appears in the schematic on P. 240. (I'm guessing you have the same copy of the SM that I have, so page numbers should match.)
The other one C161 is on P. 174, board A3, and is a 6.8 uF 35V tantalum. I'd replace it too if it looks cracked.
Yes, if these caps are bad they could indeed be causing problems. At the very least the one in the 5V PS will either pull that supply down if it is shorted or increase the ripple if it is open.
Tantalum caps are polarized electrolytics with the _positive_ lead marked, instead of the negative like most electrolytics. Obviously you have to get them in the right way round, with negative to ground. Tek advises cleaning out the plated thru-holes in the doublesided circuitboards by using a toothpick once the component has been removed. This will assure that you don't damage the traces on either side of the board. Melt the solder and stick the toothpick in there and rotate it and it will leave a nice clean hole for the new part. You can usually get away with just heating and soldering on one side (the component side in this case) of the board. The solder will flow thru the holes and make good contact.
But be prepared for it not to make any difference, it is possible that these caps are still good even if cracked! Replace them anyhow. Do you have a local component supplier? If not, DigiKey is great, it usually takes 3 or 4 days from ordering on-line to delivery to my mailbox.
I presume you have a gentle soldering iron, 35 Watts or so with a fine tip.
Before you do anything, you could check TP1558 which is right in there near the C1559 cap and see if you get the 5 V on your DMM and if this changes as the scope warms up. Also look at the box in the troubleshooting flowchart on the right side of the page on page 248, referring to the tantalum decoupling capacitors.....
;)
(ETA: It's too bad you don't live next door to me... I just checked my tantalum stash and I have both needed values in there.... But I'm not sure about the voltage rating of my 6.8 uF ones, they are just color coded not marked. The 33uf 10V one is marked though. So best order from DigiKey or hit up your local parts guy. )
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I am no expert but this is not correct from what I was taught while working on 3 phase 240 volts machinery. I was taught that you never grab anything...you use the back of your hand so in case you get zapped, and your hand closes involuntarily, you are not clinging to a hv source. Now, maybe this is only true for 3 phase circuits but...I don't think so. This saved my life once when working on some equipment (before lock-outs were invented) with the breaker off and, a note saying to leave it off. Well, someone was trying to figure out why their machine was not working and...yes...turned it on. I did get bit but, I was careful not to be in a position to have my hand close around the wire. I was also taught to use one hand only, that way the charge does not go across your heart.
Off-topic I suppose. Sorry.
Don't worry...your scope was made with quality components and meant to last. It could easily be as simple as one of those caps. You will get it figured out and then you will feel very proud for doing so. I know that I would.
Bill
I believe we are both correct.
If the AC source you are handling is something like a wire, your hand would close around it from the reflex of getting shocked, which would in a way hold you to it, but if you get zapped by AC say, on the tip of your finger, it will blow you back, and if it's strong enough, possibly blow off your finger and a toe or two if that's where it decided to leave your body at. I know someone that lost two fingers and two toes from HV AC. I could be wrong here, but I believe we are both correct.
Brian
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Yes, this could be a problem. The pic you posted... yes, that cap sure does have a crack in it. This could be bad or not, but I'd replace it anyhow. That's C1559, a 33uF 10V tantalum, and appears in the schematic on P. 240. (I'm guessing you have the same copy of the SM that I have, so page numbers should match.)
The other one C161 is on P. 174, board A3, and is a 6.8 uF 35V tantalum. I'd replace it too if it looks cracked.
Yes, if these caps are bad they could indeed be causing problems. At the very least the one in the 5V PS will either pull that supply down if it is shorted or increase the ripple if it is open.
Tantalum caps are polarized electrolytics with the _positive_ lead marked, instead of the negative like most electrolytics. Obviously you have to get them in the right way round, with negative to ground. Tek advises cleaning out the plated thru-holes in the doublesided circuitboards by using a toothpick once the component has been removed. This will assure that you don't damage the traces on either side of the board. Melt the solder and stick the toothpick in there and rotate it and it will leave a nice clean hole for the new part. You can usually get away with just heating and soldering on one side (the component side in this case) of the board. The solder will flow thru the holes and make good contact.
But be prepared for it not to make any difference, it is possible that these caps are still good even if cracked! Replace them anyhow. Do you have a local component supplier? If not, DigiKey is great, it usually takes 3 or 4 days from ordering on-line to delivery to my mailbox.
Interestingly enough, my manual, which is for my exact model, and in the correct serial number range, says that the cap on the PSU +5V rail is an electrolytic 33uf 10V..
My manual is the original one that came with the scope when the power company purchased it originally, and has the fold-out schematics and PCB layouts. It doesn't sound like we are both working with the same copies. Mine doesn't have page numbers in the diagrams section, either. just side tabs.
I presume you have a gentle soldering iron, 35 Watts or so with a fine tip.
Yes I have a 30W fine tip, and also a 6-8W fine tip battery powered one. While desoldering, I tried the 6-8W and it doesn't wanna stay hot enough so I've been using the 30W. I don't have a desoldering vacuum tool, so I made a solder sucker. On the ones where I have access to both sides, I've just been heating one side and blowing the solder thru from the other. been working great so far, but I'll have to suck it out for these caps cuz I'm not taking the boards off again. I already took the trigger and sweep boards off and cleaned everything up and inspected them today so far.
Before you do anything, you could check TP1558 which is right in there near the C1559 cap and see if you get the 5 V on your DMM and if this changes as the scope warms up. Also look at the box in the troubleshooting flowchart on the right side of the page on page 248, referring to the tantalum decoupling capacitors.....
;)
I may actually have replacements for these on hand. If I do, should I just go ahead and swap them out, or at least the PSU one first? Just in case it is causing a "ripple" or overvoltage, so it doesn't cause any further damage? Or is it unlikely that it would damage anything else running it with the possibly bad cap?
I don't have any page numbers like that, only section tabs and then the section number - page format. What section and whats on the page beside it?
(ETA: It's too bad you don't live next door to me... I just checked my tantalum stash and I have both needed values in there.... But I'm not sure about the voltage rating of my 6.8 uF ones, they are just color coded not marked. The 33uf 10V one is marked though. So best order from DigiKey or hit up your local parts guy. )
Hopefully I have some in my stash as well. I have quite a large variety of caps of all kinds. For something that inexpensive, I will order from DigiKey since we know they have high quality components, but for future orders or more expensive things, take a look at OnlineComponents.com and let me know what you think. When I ordered MJL21194's I found they had the best price on em, and they were actually the 21194's and not the G's, and are genuine ON transistors. Let me know what you think when you get around to checking them out.
But for the meantime, everything is back together, the cover is still off.... I'm going to check my stash for replacements and wait for your reply......
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Interestingly enough, my manual, which is for my exact model, and in the correct serial number range, says that the cap on the PSU +5V rail is an electrolytic 33uf 10V..
My manual is the original one that came with the scope when the power company purchased it originally, and has the fold-out schematics and PCB layouts. It doesn't sound like we are both working with the same copies. Mine doesn't have page numbers in the diagrams section, either. just side tabs.
Actually the parts list in the manual I have identifies all the tantalums and other electrolytics just as "electrolytic". The page numbers I'm citing are the pages of the .pdf file that I downloaded from the electrotanya link I provided earlier. It's a real pain that the manual itself doesn't have page numbers. Perhaps the easiest thing would be for you to download that manual too so we can refer to page numbers-- I obviously don't have the paper copy like you do. You have the advantage of seeing the good drawings of the boards, the ones in the .pdf file kind of suck. But it is nice to be able to refer to page numbers--- you could look in the .pdf file at the page numbers I cite, and then find the correct page in your paper copy.
The box referring to the tantalum decoupling caps is in the Power Supply troubleshooting flowchart for the low voltage (15, -8, 5 v) supplies. The schematic is the "power supply" tab , marked on the tab #12 in a diamond box. And the box referring to the tantalum decoupling caps is on the tab marked "+15V, +5V and -8V supplies Troubleshooting"
Yes I have a 30W fine tip, and also a 6-8W fine tip battery powered one. While desoldering, I tried the 6-8W and it doesn't wanna stay hot enough so I've been using the 30W. I don't have a desoldering vacuum tool, so I made a solder sucker. On the ones where I have access to both sides, I've just been heating one side and blowing the solder thru from the other. been working great so far, but I'll have to suck it out for these caps cuz I'm not taking the boards off again. I already took the trigger and sweep boards off and cleaned everything up and inspected them today so far.
I may actually have replacements for these on hand. If I do, should I just go ahead and swap them out, or at least the PSU one first? Just in case it is causing a "ripple" or overvoltage, so it doesn't cause any further damage? Or is it unlikely that it would damage anything else running it with the possibly bad cap?
I don't have any page numbers like that, only section tabs and then the section number - page format. What section and whats on the page beside it?
Good on the iron. I'd check the voltage at the testpoint first, (read the box on the troubleshooting chart about how they behave as the scope warms up), then I'd replace the caps if you have the right capacitance values. You can use higher voltage ratings of course, if there is room physically. You may even be able to use other capacitance values as long as they are close: the originals are 20 percent tolerance, really cheap tantalums.
Hopefully I have some in my stash as well. I have quite a large variety of caps of all kinds. For something that inexpensive, I will order from DigiKey since we know they have high quality components, but for future orders or more expensive things, take a look at OnlineComponents.com and let me know what you think. When I ordered MJL21194's I found they had the best price on em, and they were actually the 21194's and not the G's, and are genuine ON transistors. Let me know what you think when you get around to checking them out.
But for the meantime, everything is back together, the cover is still off.... I'm going to check my stash for replacements and wait for your reply......
I'd say, let the scope cool completely, then power it up, test the +5V TP1558 with the DMM right away, then let it warm up to the point where the glitching gets bad and test the TP again to see if there is any difference. Then, regardless of what you see, shut down and replace the caps if you've got suitable replacements. Then repeat the process starting with a cold scope again.
Another thing you might like to try, since the transistors are mostly all in sockets, is to wiggle them or tap on them with a wooden or plastic tapper and see if the display responds in any way. If you find one that does cause a change in the display when you tap on it, shut down the scope, carefully pull the transistor and re-seat it, maybe the it wasn't making a good connection and reseating will fix that sometimes. Lather rinse repeat.
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Actually the parts list in the manual I have identifies all the tantalums and other electrolytics just as "electrolytic". The page numbers I'm citing are the pages of the .pdf file that I downloaded from the electrotanya link I provided earlier. It's a real pain that the manual itself doesn't have page numbers. Perhaps the easiest thing would be for you to download that manual too so we can refer to page numbers-- I obviously don't have the paper copy like you do. You have the advantage of seeing the good drawings of the boards, the ones in the .pdf file kind of suck. But it is nice to be able to refer to page numbers--- you could look in the .pdf file at the page numbers I cite, and then find the correct page in your paper copy.
The box referring to the tantalum decoupling caps is in the Power Supply troubleshooting flowchart for the low voltage (15, -8, 5 v) supplies. The schematic is the "power supply" tab , marked on the tab #12 in a diamond box. And the box referring to the tantalum decoupling caps is on the tab marked "+15V, +5V and -8V supplies Troubleshooting"
Good on the iron. I'd check the voltage at the testpoint first, (read the box on the troubleshooting chart about how they behave as the scope warms up), then I'd replace the caps if you have the right capacitance values. You can use higher voltage ratings of course, if there is room physically. You may even be able to use other capacitance values as long as they are close: the originals are 20 percent tolerance, really cheap tantalums.
I'd say, let the scope cool completely, then power it up, test the +5V TP1558 with the DMM right away, then let it warm up to the point where the glitching gets bad and test the TP again to see if there is any difference. Then, regardless of what you see, shut down and replace the caps if you've got suitable replacements. Then repeat the process starting with a cold scope again.
Another thing you might like to try, since the transistors are mostly all in sockets, is to wiggle them or tap on them with a wooden or plastic tapper and see if the display responds in any way. If you find one that does cause a change in the display when you tap on it, shut down the scope, carefully pull the transistor and re-seat it, maybe the it wasn't making a good connection and reseating will fix that sometimes. Lather rinse repeat.
Within reason you can generally go larger with bulk power supply capacitors without a problem. A 47uF or even 68uF capacitor can be used in place of a 33uF in almost all situations. What you can't safely do is use a lower voltage rated capacitor.
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Just some food for thought.
Whenever troubleshooting any piece of electronic gear, it is always wise to measure the rails first thing, and as expeditiously as possible. I often pre-attach my scope/voltmeter to supply test points using spring hooks and with the unit's power off and then power the unit on just long enough to get a stable reading. Power off and then repeat for the next supply test point. If a supply has gone overvoltage, or is not regulating current, this method may minimize damage. With regard to the current topic, I agree with TK... measure the rails! Although tantalums often fail just because that's what they like to do (particularly older gen tants), tantalums do not like overvoltage, or even more so, application of reverse polarity. So check the rails first thing.
I just had one of my SG505's in a TM500 rack develop a noise. Tore it apart and probed the supplies first thing and noted one rail was noisey. The rail used a 33uf 20V tantalum. It was one of the old early tants, a big honkin' thing the size of a large peanut M&M with horizontal color stripes (in familiar M&M colors). There was what looked like a tear dropped shaped solder blob stuck to the side of the tant. Upon closer inspection, a very small hole had formed in the side of the tant's "candy coating" and the apparently molten at the time metal blob had oozed thru the almost microscopic hole and solidified. A very light and unfamiliar metal was that blob. Anyone who has ever worked on electronic equipment that uses tants will have many stories to tell regarding them. Definitely a love hate thing.
I ordered new tants to recap all my SG505's, but in order to put this unit back in service, I temporarily replaced the tant with a 47uf 35V electrolytic (1/4 the size of the tant) and then tacked a .1uf ceramic to the back of the board in parallel with the electrolytic. This parallel combination will work well in most applications that use a tant, and some of the newer electrolytics approach or exceed the HF performance of early gen tantalums. A functioning electrolytic will always perform better than a non-functioning tantalum!
Also, regarding probes. Yes indeed, expensive probes are nice and sometimes necessary, and I agree with everything MarkE has said about them. However, when repairing a piece of equipment where one might have to get a bit creative just to get a probe hook attached to a component lead or other measurement point that is not easy to get to, I use the cheap probes. Most of the time you are looking for a DC level, noise, or just the presence of a specific signal, and the cheap probes are fine for this. If a probe hook gets bent or broken from somewhat abusive probing, well, it was just a cheap probe, no worries.
Now, if you are looking at a fast rise time digital signal, switching supply, something you cant load, a circuit that is screaming with an unwanted HF oscillation, or you need absolute measurement precision, that is the time to break out the expensive or active probes. And since you did not use them as your "daily driver", they are always in great shape (and of course you will slow down and drive more carefully when using the expensive probes).
Anyway, like I said, just food for thought...
PW
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Just some food for thought.
Whenever troubleshooting any piece of electronic gear, it is always wise to measure the rails first thing, and as expeditiously as possible. I often pre-attach my scope/voltmeter to supply test points using spring hooks and with the unit's power off and then power the unit on just long enough to get a stable reading. Power off and then repeat for the next supply test point. If a supply has gone overvoltage, or is not regulating current, this method may minimize damage. With regard to the current topic, I agree with TK... measure the rails! Although tantalums often fail just because that's what they like to do (particularly older gen tants), tantalums do not like overvoltage, or even more so, application of reverse polarity. So check the rails first thing.
I just had one of my SG505's in a TM500 rack develop a noise. Tore it apart and probed the supplies first thing and noted one rail was noisey. The rail used a 33uf 20V tantalum. It was one of the old early tants, a big honkin' thing the size of a large peanut M&M with horizontal color stripes (in familiar M&M colors). There was what looked like a tear dropped shaped solder blob stuck to the side of the tant. Upon closer inspection, a very small hole had formed in the side of the tant's "candy coating" and the apparently molten at the time metal blob had oozed thru the almost microscopic hole and solidified. A very light and unfamiliar metal was that blob. Anyone who has ever worked on electronic equipment that uses tants will have many stories to tell regarding them. Definitely a love hate thing.
I ordered new tants to recap all my SG505's, but in order to put this unit back in service, I temporarily replaced the tant with a 47uf 35V electrolytic (1/4 the size of the tant) and then tacked a .1uf ceramic to the back of the board in parallel with the electrolytic. This parallel combination will work well in most applications that use a tant, and some of the newer electrolytics approach or exceed the HF performance of early gen tantalums. A functioning electrolytic will always perform better than a non-functioning tantalum!
Also, regarding probes. Yes indeed, expensive probes are nice and sometimes necessary, and I agree with everything MarkE has said about them. However, when repairing a piece of equipment where one might have to get a bit creative just to get a probe hook attached to a component lead or other measurement point that is not easy to get to, I use the cheap probes. Most of the time you are looking for a DC level, noise, or just the presence of a specific signal, and the cheap probes are fine for this. If a probe hook gets bent or broken from somewhat abusive probing, well, it was just a cheap probe, no worries.
Now, if you are looking at a fast rise time digital signal, switching supply, something you cant load, a circuit that is screaming with an unwanted HF oscillation, or you need absolute measurement precision, that is the time to break out the expensive or active probes. And since you did not use them as your "daily driver", they are always in great shape (and of course you will slow down and drive more carefully when using the expensive probes).
Anyway, like I said, just food for thought...
PW
One thing to be a bit careful about is that there are a lot of circuits that rely on the ESR of the capacitors for stability. A really low ESR may break a regulator circuit causing it to oscillate. Those old "candy wrapper" tantalums tended to have ESRs in the 2-10 Ohm range.
I like the robustness of passive probes. A colleague of mine set me up with some really sweet passive probes that I can clip almost anywhere and they perform very politely. The oscilloscope trace below was snapped with one hooked to a 5V < 1ns risetime CMOS logic circuit.
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One thing to be a bit careful about is that there are a lot of circuits that rely on the ESR of the capacitors for stability. A really low ESR may break a regulator circuit causing it to oscillate. Those old "candy wrapper" tantalums tended to have ESRs in the 2-10 Ohm range.
I like the robustness of passive probes. A colleague of mine set me up with some really sweet passive probes that I can clip almost anywhere and they perform very politely. The oscilloscope trace below was snapped with one hooked to a 5V < 1ns risetime CMOS logic circuit.
MarkE,
Yes, but the tants claim to fame when they first arrived was their low inductance/HF performance. A "one stop shop" for decoupling applications.
What model probe?
PW
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They didn't quite live up to that claim.
My colleague custom made the probes he gave me. They are quite handy.
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Actually the parts list in the manual I have identifies all the tantalums and other electrolytics just as "electrolytic". The page numbers I'm citing are the pages of the .pdf file that I downloaded from the electrotanya link I provided earlier. It's a real pain that the manual itself doesn't have page numbers. Perhaps the easiest thing would be for you to download that manual too so we can refer to page numbers-- I obviously don't have the paper copy like you do. You have the advantage of seeing the good drawings of the boards, the ones in the .pdf file kind of suck. But it is nice to be able to refer to page numbers--- you could look in the .pdf file at the page numbers I cite, and then find the correct page in your paper copy.
The box referring to the tantalum decoupling caps is in the Power Supply troubleshooting flowchart for the low voltage (15, -8, 5 v) supplies. The schematic is the "power supply" tab , marked on the tab #12 in a diamond box. And the box referring to the tantalum decoupling caps is on the tab marked "+15V, +5V and -8V supplies Troubleshooting"
I downloaded that manual so now we are able to easily toss page numbers around. If you ever need a higher quality image of anything out of that book, or any of the materials that I have, let me know and I will scan it and put it up on my photobucket.
Good on the iron. I'd check the voltage at the testpoint first, (read the box on the troubleshooting chart about how they behave as the scope warms up), then I'd replace the caps if you have the right capacitance values. You can use higher voltage ratings of course, if there is room physically. You may even be able to use other capacitance values as long as they are close: the originals are 20 percent tolerance, really cheap tantalums.
I'd say, let the scope cool completely, then power it up, test the +5V TP1558 with the DMM right away, then let it warm up to the point where the glitching gets bad and test the TP again to see if there is any difference. Then, regardless of what you see, shut down and replace the caps if you've got suitable replacements. Then repeat the process starting with a cold scope again.
All the tantalums I have are in the nF/pF range. The only larger ones I have are molded and are way too big. I have a huge variety of electrolytics, and also ceramic disc caps. I could go the temp route of what picowatt was saying, but I'd rather do replacements with exact value/type replacements. I am going to go thru first off and do what picowatt suggested with pre attaching the dmm to the rail test points and quickly power on to see first of all if the voltages are correct. If they are, I will let it warm up and test TP1558. again.
Another thing you might like to try, since the transistors are mostly all in sockets, is to wiggle them or tap on them with a wooden or plastic tapper and see if the display responds in any way. If you find one that does cause a change in the display when you tap on it, shut down the scope, carefully pull the transistor and re-seat it, maybe the it wasn't making a good connection and reseating will fix that sometimes. Lather rinse repeat.
As I was cleaning all the boards, I did exactly that (wiggling and making sure they are fully seated) to all the transistors/fets/round IC's. maybe one of them does still have a bad connection still. what do you think of the idea of putting a wee bit of dielectric "grease" on the leads? I've used it in a ton of automotive connections and even some household connections such as breakers to ensure a good connection and no corrosion. I'm sure you already know that it's not conductive except when it's a very thin layer between contacts. I already did this with all of the coax connections that I messed with.. the leads off of them had a little bit of a blackened layer formed around them where the connections weren't full contact, so I cleaned them off a little with a light rub with 1000grit sandpaper and a med bristle toothbrush.
Also, I managed to find another bad capacitor. this time it was under the HV cover of the IC and is a multilayer ceramic.
C1476 of A9 CRT circuit. 110V regulated. also one that goes to ground.... .1uf 200V +80-20%.
None of my component sites have this exact cap, and ebay doesn't even have them.
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00167_zpsfvycu68n.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00166_zpss6er2akh.jpg
(It may be a little hard to tell, but the lead with the "scratch" looking mark above it appears to be split apart in a diagonal manner. On the side that I can't get the cam in to show, there is a chunk taken out of the lead which looks like it was caused by an arc. Possible that the cap started to go bad, heated, split the lead, and then the tiny gap created in the lead caused an arc which melted the lead? If so, this could very well be the source of my perpetual noise, right? It's in the CRT circuit, and the arcing in the gap would cause a visual noise on screen.)
Here are my options:
(sorry, had to break up the links so they wouldn't expand the page horizontally...)
http://www.digikey.com/product-search/en?pv14=14&
FV=fff40002%2Cfff8000b%2Cc000c%2C340025%2C340026%2C340027%2C340028%2C340029%2C34002b%2C34002c%2C34002d%2C34013c%2C340168%2C34
01a8%2C3401aa%2C3401ac%2C3402c0%2C340364%2C380002%2C38000e%2C1140050&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&
quantity=0&ptm=0&fid=0&pageSize=25
http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors
/_/N-5g8mZscv7?P=1z0wqusZ1z0wpxxZ1z0wpygZ1z0wq52Z1z0wplvZ1z0wps8Z1z0wplsZ1z0wqu1Z1z0wl0jZ1z0wqtpZ1z0wqg1Z1z0wqtyZ1z0wq34Z1z0wk75Z1yzut9
8Z1z0wxf7Z1z0vvr9Z1z0x8e0Z1z0x8eaZ1z0wx3tZ1z0x86hZ1z0wxoyZ1z0x810Z1z0wdmxZ1yyeqdfZ1z0wd6qZ1yz7fw1Z1z0wdl4Z1z0x86rZ1z0x43wZ1z0wx10Z1z0x8g
xZ1yz7f70Z1z0wx8wZ1z0wf8bZ1z0wl3nZ1yx7yinZ1z0wxeoZ1yyy7xyZ1yzml5fZ1z0x8elZ1z0wxey
http://www.allelectronics.com/make-a-store/item/rm-104c/0.1uf-500v-radial-multi-layer-ceramic-capacitor/1.html
Anyone else know of any possible reliable sites? Onlinecomponents doesn't have any caps that are close to equivalent.
The second one on Mouser is out of the question. $23 for a single cap... and the one on Allelectronics isn't the right tolerance. it's 20%, not -20+80%.
This replacement part is going to dictate where I end up placing my order from. All of these sites have the two values of tantalums that I need.
If there are any other specific areas of the scope that I should pick up some replacement caps or transistors for, let me know. I already plan to get a few extra tantalums just to have. I'm going to see what the most common values of those this scope uses and pick up some to have.
MarkE - seems like that guy made you some great probes! Thanks for the pointers.
picowatt - thanks for the input. I'll definitely try testing the rails with that method first. Wouldn't wanna burn up even more components if I do have an overvoltage issue somewhere!
Brian
p.s. Sorry I passed out early on you guys last night.
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I downloaded that manual so now we are able to easily toss page numbers around. If you ever need a higher quality image of anything out of that book, or any of the materials that I have, let me know and I will scan it and put it up on my photobucket.
Good, thanks. It would be nice to have some good images of the board layouts. As you can see, the ones in the pdf really are bad and hard to read.
All the tantalums I have are in the nF/pF range.
That seems odd. They must be very tiny. I think the smallest ones I've got are 100 nF. A 68 uF 16V one is about the size of a large pea. This is the great advantage of tantalums, in addition to their fast response: they are really physically small for the capacitance value.
The only larger ones I have are molded and are way too big. I have a huge variety of electrolytics, and also ceramic disc caps. I could go the temp route of what picowatt was saying, but I'd rather do replacements with exact value/type replacements. I am going to go thru first off and do what picowatt suggested with pre attaching the dmm to the rail test points and quickly power on to see first of all if the voltages are correct. If they are, I will let it warm up and test TP1558. again.
Good. You could also test the other power supply test points while you are at it.
As I was cleaning all the boards, I did exactly that (wiggling and making sure they are fully seated) to all the transistors/fets/round IC's. maybe one of them does still have a bad connection still. what do you think of the idea of putting a wee bit of dielectric "grease" on the leads? I've used it in a ton of automotive connections and even some household connections such as breakers to ensure a good connection and no corrosion. I'm sure you already know that it's not conductive except when it's a very thin layer between contacts. I already did this with all of the coax connections that I messed with.. the leads off of them had a little bit of a blackened layer formed around them where the connections weren't full contact, so I cleaned them off a little with a light rub with 1000grit sandpaper and a med bristle toothbrush.
The very idea gives me the willies. I would definitely _not_ recommend that you put any kind of compound on anything. Clean it off the coax connectors!
The black oxide layer is silver oxide forming on the silver plating of the connectors. Cleaning carefully can remove this, but you don't want to remove the silver plating by being too aggressive with sandpaper!
Also, I managed to find another bad capacitor. this time it was under the HV cover of the IC and is a multilayer ceramic.
C1476 of A9 CRT circuit. 110V regulated. also one that goes to ground.... .1uf 200V +80-20%.
None of my component sites have this exact cap, and ebay doesn't even have them.
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00167_zpsfvycu68n.jpg (http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00167_zpsfvycu68n.jpg)
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00166_zpss6er2akh.jpg (http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00166_zpss6er2akh.jpg)
(It may be a little hard to tell, but the lead with the "scratch" looking mark above it appears to be split apart in a diagonal manner. On the side that I can't get the cam in to show, there is a chunk taken out of the lead which looks like it was caused by an arc. Possible that the cap started to go bad, heated, split the lead, and then the tiny gap created in the lead caused an arc which melted the lead? If so, this could very well be the source of my perpetual noise, right? It's in the CRT circuit, and the arcing in the gap would cause a visual noise on screen.)
I have been thinking all along that the regularity of the glitch and the steady rate no matter the scope settings seemed like an arcing problem. You may have found the trouble.
Here are my options:
(sorry, had to break up the links so they wouldn't expand the page horizontally...)
http://www.digikey.com/product-search/en?pv14=14& (http://www.digikey.com/product-search/en?pv14=14&)
FV=fff40002%2Cfff8000b%2Cc000c%2C340025%2C340026%2C340027%2C340028%2C340029%2C34002b%2C34002c%2C34002d%2C34013c%2C340168%2C34
01a8%2C3401aa%2C3401ac%2C3402c0%2C340364%2C380002%2C38000e%2C1140050&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&
quantity=0&ptm=0&fid=0&pageSize=25
http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors (http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors)
/_/N-5g8mZscv7?P=1z0wqusZ1z0wpxxZ1z0wpygZ1z0wq52Z1z0wplvZ1z0wps8Z1z0wplsZ1z0wqu1Z1z0wl0jZ1z0wqtpZ1z0wqg1Z1z0wqtyZ1z0wq34Z1z0wk75Z1yzut9
8Z1z0wxf7Z1z0vvr9Z1z0x8e0Z1z0x8eaZ1z0wx3tZ1z0x86hZ1z0wxoyZ1z0x810Z1z0wdmxZ1yyeqdfZ1z0wd6qZ1yz7fw1Z1z0wdl4Z1z0x86rZ1z0x43wZ1z0wx10Z1z0x8g
xZ1yz7f70Z1z0wx8wZ1z0wf8bZ1z0wl3nZ1yx7yinZ1z0wxeoZ1yyy7xyZ1yzml5fZ1z0x8elZ1z0wxey
http://www.allelectronics.com/make-a-store/item/rm-104c/0.1uf-500v-radial-multi-layer-ceramic-capacitor/1.html (http://www.allelectronics.com/make-a-store/item/rm-104c/0.1uf-500v-radial-multi-layer-ceramic-capacitor/1.html)
Anyone else know of any possible reliable sites? Onlinecomponents doesn't have any caps that are close to equivalent.
The second one on Mouser is out of the question. $23 for a single cap... and the one on Allelectronics isn't the right tolerance. it's 20%, not -20+80%.
This replacement part is going to dictate where I end up placing my order from. All of these sites have the two values of tantalums that I need.
The one from Allelectronics should be fine. Don't worry about the tolerance, you are now dealing with modern components that will be much closer to the printed value than those ancient ones in the scope. C1476 appears in the schematic on page 228 of the .pdf SM and appears to be an ordinary decoupling cap for the Emitter of Q1478. This should be a "nothing special" capacitor and the one from Allelectronics will work perfectly here.
The Q1478 transistor is a PNP silicon, and 2n5401 is the generic cross for that one, should you need to replace it. This is a HV silicon amplifier and the NTE equivalent is NTE288. Cheap and easy to find if you need to replace it. Check that associated resistor R1476 also for off-value.
http://www.reprise.com/host/tektronix/reference/find_transistor.asp (http://www.reprise.com/host/tektronix/reference/find_transistor.asp)
If there are any other specific areas of the scope that I should pick up some replacement caps or transistors for, let me know. I already plan to get a few extra tantalums just to have. I'm going to see what the most common values of those this scope uses and pick up some to have.
MarkE - seems like that guy made you some great probes! Thanks for the pointers.
picowatt - thanks for the input. I'll definitely try testing the rails with that method first. Wouldn't wanna burn up even more components if I do have an overvoltage issue somewhere!
Brian
p.s. Sorry I passed out early on you guys last night.
This is where a Variac can come in handy. For general troubleshooting reference: if you have a device that is blowing the main fuse, for example, you remove the fuse and put an ammeter across the fuse contacts, then use the Variac to slowly run up the line input voltage from zero to your local mains voltage. If the current draw indicated on the ammeter approaches 90 percent of the fuse value.. STOP!
If you suspect a severe power supply fault, you can do the same thing, while monitoring the suspect power supply with a voltmeter. Again, if the output voltage of the monitored supply begins to look like it is going to exceed the spec value + tolerance, then STOP increasing input voltage from the Variac.
However I don't think your problem fits in this category. The scope seems to be working, basically, at least so far. Once these suspect caps are replaced we can go further into the various features and functions to see if there is anything else wrong.
I never did see what the CH2 trace from the calibrator looks like. I'm presuming it is also mostly OK but with the same glitching as you've shown on the CH1 trace.
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Brian,
I have not been following this thread much, and I don't even know what model 'scope you are working on.
That said, I looked at the jpg's you posted last of a few caps and saw none that were visually concerning. The tant with the crack at the base/side is not necessarily an indication that it is bad. During manufacture, one lead is attached to the bottom of a pellet and the other lead runs up the side to the top of the pellet and then the whole thing is dipped. What I see in the image posted in your last post is a tant with the lead going up the side slightly separated near the base with the encapsulation slightly cracked. If it is not shorted (which you can test with an ohmmeter) keep it in mind but move on for now.
The next jpg I looked at was of an orangish brown cap that looked more like a poly cap than a multilayer ceramic. Unless you have a manual that specifies it as a multilayer ceramic, I would assume it is a poly cap. Again, I see no visual evidence that would lead me to believe the cap is bad. There is a bit of cracking of the encapsulation around one lead, but this is not uncommon nor an indication that it is bad. In another image, I saw another poly looking cap with a slight scratch near one lead that again did not indicate the cap was bad. I suspect the scratch was from someone probing the lead of that cap that might have scratched it with a probe tip (previous repair attempt?).
Keep in mind that although resistors typically look bad when they have been thermally stressed (except for the flameproof variety) with signs of heat damage to the resistor, PCB, etc, failed caps often show no outwardly visual clues as to their status (other than the rather "dramatic" failures).
Now, you talked about a ceramic cap with one lead burnt open with signs of arcing. That is a major concern. First, you need to look at the schematic and determine what that cap was there for. Is it a supply decoupling cap or is it in the horizontal/HV oscillator section? Although it is possible that the cap "just went bad", it is also possible that the cap saw huge amounts of AC current or an over voltage that shorted the cap and then blew the lead open. For example, if the cap is a supply decoupler, it is possible a failed regulator, or another failed cap upstream of this blown cap, caused an over voltage or large AC oscillation to appear on the failed cap prior to failure. If that is the case, simply replacing that cap will not fix the initial problem that caused that cap to fail.
As I said, you will need to know what that failed cap's function was in the circuit to begin to do a forensic analysis of why it failed. As well, you will need to know what DC and AC voltage appeared across it. Unfortunately, to be able to "see" what is going on at that caps point in the circuit, you will need a 'scope.
With any used piece of electronic equipment, it is critical that the supplies be checked very first thing. Both for "quantity" and "quality". A supply rail might measure correctly with a DC voltmeter but a check with a 'scope might reveal noise or oscillations riding on that DC that you would not see without using a 'scope. Also keep in mind that when probing around universal supplies (switchers) there are different grounds (commons) to contend with, some of which are mains connected and usually indicated on the schematic. One must be very careful when working on the primary side of these supplies, particularly without the use of an isolation transformer at the AC line input.
Repairing this 'scope might be a bit much for you to chew on at this time. It is a shame that you cannot find a functioning used scope or even a low cost USB scope to get you more acquainted with 'scopes in general (and to use in repairing this and future used equipment)
PW
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The words "sandpaper" and "oscilloscope", when used together, makes all that is me "cringe"...
Similarly, "grease" and "oscilloscope" do not go well together, although in reference to switch ball detents, there may be some utility.
"Sandpaper" and "silver plating" also invoke a very disagreeable response within me.
PW
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Great post PW. I also did not think the caps looked like they had any problems. One suggestion for Brian when he checks the rails is to put the multimeter on DC and then on AC. I believe that the multimeter on AC would pick up any glitching on a supply rail within limits. However, careful because some "cruder" DC supply rails may have some AC on them which is normal. I apologize because I am flying blind and haven't looked at the schematic.
In my days we would sprinkle tantalum caps around a board for the bulk decoupling and then put a 0.1 uF ceramic at the power pin for the chips. I have to confess I didn't even know that they were also good for HF decoupling, all I knew was that it was just standard practice to sprinkle them around.
It's interesting (fun?) to look at the "decoupling and regulation war zone" around a motherboard CPU socket these days. I am 25 years out of the design game which is 100 years in non-tech time.
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Good, thanks. It would be nice to have some good images of the board layouts. As you can see, the ones in the pdf really are bad and hard to read.
When I change the zoom to 100%, everything seems perfectly readable. If you don't have anything visible showing your % zoom, try the "view" menu. Depending on your program, it might be under zoom or magnification, and turn it up some until it's readable. If you are using Adobe Reader, go to the "View" menu, -"show/hide" - "toolbar items" - "select & zoom" and then check "zoom value" and the two above it. That'll add it to the toolbar so you can change the zoom much easier. :)
That seems odd. They must be very tiny. I think the smallest ones I've got are 100 nF. A 68 uF 16V one is about the size of a large pea. This is the great advantage of tantalums, in addition to their fast response: they are really physically small for the capacitance value.
Yep they are pretty tiny.
The very idea gives me the willies. I would definitely _not_ recommend that you put any kind of compound on anything. Clean it off the coax connectors!
The black oxide layer is silver oxide forming on the silver plating of the connectors. Cleaning carefully can remove this, but you don't want to remove the silver plating by being too aggressive with sandpaper!
Will do, sir. Will clean it all off with alcohol. I didn't rub the sandpaper on it much at all, I didn't even take off all the silver oxide layer. I just rubbed it gently around the contact one time to clean off any debris.
I have been thinking all along that the regularity of the glitch and the steady rate no matter the scope settings seemed like an arcing problem. You may have found the trouble. The one from Allelectronics should be fine. Don't worry about the tolerance, you are now dealing with modern components that will be much closer to the printed value than those ancient ones in the scope. C1476 appears in the schematic on page 228 of the .pdf SM and appears to be an ordinary decoupling cap for the Emitter of Q1478. This should be a "nothing special" capacitor and the one from Allelectronics will work perfectly here.
Well now that I know that it doesn't need to be anything special, I will check my boxes for a quick replacement! I most likely have one of those, as I remember vividly having quite a large number of .1uf caps of that type. lets just hope that I have at least one that's 200V or more! Then if that was the problem this whole time, I can just get that one done and over with, leave the other two for now, and give 'er a shot! of course I'm still going to check the rail voltages before and after.
One thing I did notice, which would go hand in hand with this bad cap: after it warmed up the first time, it started with the noise. I let it cool for a while and then powered it back up, and it was still there. Therefore saying the damage happened when it warmed up the first time round, and didn't go away, so this little cap arcing issue that melted the lead could very well be my problem. let's hope it's my only problem, and the other two caps are just cosmetic issues! (I'll still replace them, though. If it was a part that was more than a dollar and was only cosmetic, I would leave it. But I can get 2 or 3 good quality tant caps for a dollar....)
The Q1478 transistor is a PNP silicon, and 2n5401 is the generic cross for that one, should you need to replace it. This is a HV silicon amplifier and the NTE equivalent is NTE288. Cheap and easy to find if you need to replace it. Check that associated resistor R1476 also for off-value.
Will checking the Hfe on a DMM actually tell me if a transistor is bad? I know sometimes I may not be able to find the datasheet for the original cap, but the generics should still have close to the same Hfe range, right? I will def check the resistor as well. I checked a bunch on the preamp board and at the inputs, and they were fine.
http://www.reprise.com/host/tektronix/reference/find_transistor.asp (http://www.reprise.com/host/tektronix/reference/find_transistor.asp)
That is a great tool to have! thanks for pointing me to it!
This is where a Variac can come in handy. For general troubleshooting reference: if you have a device that is blowing the main fuse, for example, you remove the fuse and put an ammeter across the fuse contacts, then use the Variac to slowly run up the line input voltage from zero to your local mains voltage. If the current draw indicated on the ammeter approaches 90 percent of the fuse value.. STOP!
If you suspect a severe power supply fault, you can do the same thing, while monitoring the suspect power supply with a voltmeter. Again, if the output voltage of the monitored supply begins to look like it is going to exceed the spec value + tolerance, then STOP increasing input voltage from the Variac.
However I don't think your problem fits in this category. The scope seems to be working, basically, at least so far. Once these suspect caps are replaced we can go further into the various features and functions to see if there is anything else wrong.
Well unfortunately I do not have a variac yet. Closest thing I have is a dimmer switch, and there's no way I'm going to use that on any equipment! haha different when using for some oddball experiment, like I did for the mini Kapanadze before I had a clue...
I never did see what the CH2 trace from the calibrator looks like. I'm presuming it is also mostly OK but with the same glitching as you've shown on the CH1 trace.
If the power supply rails are OK, or if I need to replace that cap before running it, and have a replacement, I will make another vid with both CH1 and CH2. Rob, the guy I got it from, said that there was something minor wrong with CH2.. and I remember that the trace was almost flat (had no vertical amplitude) when I first turned it on before I did any cleaning or anything to it. Remember? I should have but didnt make a vid of it, but that was when I had a ton of noise from the switches, and the trace was also very, very dull, even when I had the intensity turned way up. ( don't know why it was like that, but whatever cleaning I did fixed it, cuz in the vids I made it was nice and bright.)
If for some reason your copy of the manual is unable to be zoomed in on, let me know and I will scan the diagrams that we are dealing with for you.
Brian
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Going back to the scope, there seems to be a problem with the raster scan. So there must be test points for the horizontal and vertical rasters. I am using a very liberal interpretation of the term "raster." More specifically, there may be a three test points for the vertical raster. The first one would be the DC vertical bias signal. Then next one would be the input signal. And the third one would be the DC bias plus the input signal. Presumably the DC bias signal goes "off screen" during the horizontal blanking interval. I don't know the guts of scopes enough to know if the beam is modulated off during the horizontal blanking interval also. If it is there may be a separate test point for that, and that would form part of the "raster signal matrix."
When the scope is giving a good display at the slower time base, you should be able to scope (I realize you need a second scope to do this) something akin to a "TV signal" for the two rasters. I am going to assume that during the horizontal flyback interval the vertical raster is supposed to be "down and off the screen." Then when the time base is faster, something is corrupting the regular raster waveforms. It looks like there may be a problem during the blanking interval.
If you did indeed observe a corruption in the raster waveforms, then you could trace the signal and follow it back through the schematic.
Higher raster speeds presumably mean more stress on semiconductor components. Perhaps there is a transistor somewhere in the signal path that starts to croak from the stress above a certain frequency.
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PW and MH -
I know that you can't really see it, even with the close up of that .1uf 200V cap, but from the other side and various angles I can easily see that there is a split in the lead and a chunk melted out of the lead. I tried to get a pic of it using some small inspection mirrors but I just can't get the angle.
Either way that cap is getting replaced, and so is at least one of the cosmetically damaged tantalums, regardless of whether it is bad or not. I'm perfectly capable of soldering in tight places.
I am still just learning the ropes of equipment repair, so I appreciate all the pointers and pointing out what the proper order of operations and methods are for checking a piece of equipment. I will definitely be hooking a DMM up to the V-rail test point and ground and powering it on for a min, then letting it cool for a few min, and checking the next point, doing so with both DC and AC settings.
Yes, sandpaper and equipment don't really go together. I know not to even bother now. However, just for an FYI, it was 1000grit sandpaper, which feels more like a piece of paper than it does sandpaper. I know not to touch the PCB or any actual components with it, as it would remove the protective layers. All I use for cleaning is IPA, and Deoxit where absolutely necessary, like inside of pots or switches that aren't exposed to where I can easily get a camel hair paintbrush and IPA in, and just spraying with IPA won't do the trick. I've also gotten the pointer from MH about using a tiny drop of WD40 and letting it sit for a couple days. What wasn't mentioned, and what I would likely do following these couple of days and a couple minutes of use to make sure it's done its job, is clean off the WD with some IPA.
Brian
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the other two caps are just cosmetic issues! (I'll still replace them, though)
I would strongly advise against that. If there are little trim pots all over the boards in your scope that typically means that the boards had to be tuned and aligned with the trimpots as part of the manufacturing process. Changing a cap could adversely affect the tuning and alignment of your scope. I am being cautious and very generic in my statement.
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Great post PW. I also did not think the caps looked like they had any problems. One suggestion for Brian when he checks the rails is to put the multimeter on DC and then on AC. I believe that the multimeter on AC would pick up any glitching on a supply rail within limits. However, careful because some "cruder" DC supply rails may have some AC on them which is normal. I apologize because I am flying blind and haven't looked at the schematic.
In my days we would sprinkle tantalum caps around a board for the bulk decoupling and then put a 0.1 uF ceramic at the power pin for the chips. I have to confess I didn't even know that they ware also good for HF decoupling, all I knew was that it was just standard practice to sprinkle them around.
It's interesting (fun?) to look at the "decoupling and regulation war zone" around a motherboard CPU socket these days. I am 25 years out of the design game which is 100 years in non-tech time.
MH,
The AC voltmeter idea would be fine for rails, but if the issue is with the switcher or the sweep/HV supply, I'd want a decent probe and 'scope.
A bit off topic, but my favorite tantalum story is with regard to a PA mixing console a friend owned.
About 20 years ago or so, I visited this friend while out of town on business. He was bummed because he had a 3 or 4 year old low cost, but nice looking, 28X4 PA mixer with a shorted +18V rail. He took it in for repair but was told that due to the low cost method used to construct the board (all channels on one massive motherboard) it was impossible to isolate which of the literally hundreds of tants used at every IC for decoupling was shorting the rail. He was told all tants would have to be changed at a cost more than the board was worth. The shorted cap made the supply go into current limit so the entire rail was down at all measurement points. Were I at home, I would have connected a constant current supply to the rail feed and used a comparator probe or a 6 digit voltmeter to follow the short (using the PC traces as a CSR and noting polarity).
Long story short, we took the board apart (every knob and control nut had to be removed), unplugged the supply from the motherboard and using a 12V gel cell (i.e., a high current source) and clip leads he had laying around, I attached the gel cell to the +18V rail for a few seconds and then BANG! There went the bad cap! The ugliest smelling/tasting curly trails of black "something" wafted downward as the room slowly cleared of smoke. We replaced that single bad (and now exploded/mostly missing) cap and reassembled the board. A thorough test showed all preamps, EQ's, etc, to be working just fine. He was still using it eight years later when I was on another out of town trip.
PW
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PW, ;)
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I would strongly advise against that. If there are little trim pots all over the boards in your scope that typically means that the boards had to be tuned and aligned with the trimpots as part of the manufacturing process. Changing a cap could adversely affect the tuning and alignment of your scope. I am being cautious and very generic in my statement.
And you don't want to take a chance of cracking or pulling out a plated thru hole or lifting a pad if you don't have to.
Brian said he is blowing out the solder (I assume with compressed air or Dust off) which is OK if you know where the solder is going! Don't let it blow onto a board somewhere where it will short out something causing another problem.
When solder sucking or blowing out plated thru holes, it may be necessary to resolder the lead and do it again if you don't see daylight around the lead the first time. Resoldering allows the joint to wet again. Also, it is always a good idea to snap the lead loose from the side of the plated thru hole using a small flat bladed screwdriver or small needle nose plier and sideways force. Resist the temptation to pull on the part until you can easily wiggle all leads, otherwise you may pull out a small copper cylinder that was once the thru hole plating. Sometimes it is best just to carefully cut the part's leads first and then pull each lead out of the board one at a time while applying heat. After all the leads are out, the hole can be cleared of solder (via sucking, blowing, or wicking). This is particularly advisable with leads that are a tight fit in the PCB hole that do not allow sucking out the solder all that well.
PW
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PW:
Funny story. That repair tech guy had a fail. My first thought was to take my variable bench power supply and inject some current and put a few watts in and then do a "laying on of hands" to find the cap acting like a toasty resistor. Your way was quite dramatic.
My semi-related story was running a boom box off a Radio Shack power inverter circa 1980. This was in a big private bus going down the highway. We heard this incredibly loud boom. It was so loud that we all thought a tire blew out. There was a big non-polarized electrolytic cap (I think) in the inverter that blew up.
Yes about those tants. They look like mysterious gooey stuff must be encapsulated in there. A dangerous thing is inserting radial tantalum caps manually into boards on a push line. A very nice lady in a blue frock may make a mistake and it's had to detect. I don't think a reversed-biased tantalum cap turns into a gooey mess right away when it is wrongly inserted so it can make it into a shipping box.
MileHigh
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PW:
Funny story. That repair tech guy had a fail. My first thought was to take my variable bench power supply and inject some current and put a few watts in and then do a "laying on of hands" to find the cap acting like a toasty resistor. Your way was quite dramatic.
My semi-related story was running a boom box off a Radio Shack power inverter circa 1980. This was in a big private bus going down the highway. We heard this incredibly loud boom. It was so loud that we all thought a tire blew out. There was a big non-polarized electrolytic cap (I think) in the inverter that blew up.
Yes about those tants. They look like mysterious gooey stuff must be encapsulated in there. A dangerous thing is inserting radial tantalum caps manually into boards on a push line. A very nice lady in a blue frock may make a mistake and it's had to detect. I don't think a reversed-biased tantalum cap turns into a gooey mess right away when it is wrongly inserted so it can make it into a shipping box.
MileHigh
MH,
With the supply folded back, nothing was getting all that warm (including the supply).
And yes, a backwards installed tant tends to first get a bit warm, then get very noisey, and then finally will usually short. If they are of sufficiently high V rating relative to the rail, they can, as you say, survive long enough to QC the equipment and get it out the door.
And then, of course, there is infant mortality...
PW
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@MH and PW: I suggest you look at the videos Brian has posted. The scope is a Tek 465 and the SM can be downloaded from the link I posted earlier in the thread, so that you can be "on the same page" as we are, so to speak.
I've located the caps in question on the parts list and on the schematics in that version of the SM. The questionable C1476 cap referred to is indeed listed as a ceramic and the photo listing in the parts source that Brian found looks very much like the cap photo on the board. It is a multilayer ceramic, and its position in the circuit leads me to think that it could indeed be causing at least one of the glitches that he has shown in the videos.
All help is of course appreciated, and I'm especially glad that PW is interested. He may be able to tell much more from the schematic and the behaviour as shown in the video than I can.
Those old doublesided circuit boards are usually very robust. PW's advice about clipping the component leads off very short is a good one, and then the remainder can be pushed out with a wooden toothpick while heating the pad with the iron. This process is actually recommended by Tek for the plated thru-holes, to clear them for reinstallation of a new component.
Making sure that the removed solder doesn't get on anything is a rather elementary caution.
@Brian: the board images that I see: some of them are quite readable but others are not. I really don't think it's a problem with my software or the use of it.
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I would strongly advise against that. If there are little trim pots all over the boards in your scope that typically means that the boards had to be tuned and aligned with the trimpots as part of the manufacturing process. Changing a cap could adversely affect the tuning and alignment of your scope. I am being cautious and very generic in my statement.
I think this is unlikely in this case. Take a look at the schematic to see the function of these tantalums in the circuit.
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I think this is unlikely in this case. Take a look at the schematic to see the function of these tantalums in the circuit.
TK,
Where is a video of the current state of this scope? Last one I saw was with severe blooming with what looked like horiz scan issues. Is there a newer video showing the scope functioning a bit better?
Has Brian posted any DC measurements of at least the LV rails? 'Tis the best place to start.
I doubt that tant is the only +5 rail decoupling cap, but if it is noisey, it might be glitching the line. Temporarily replacing it with an electrolytic or even just attaching one across the rail may assist diagnostics. In the absence of a scope for diagnostics, MH's suggestion of looking at the 5V rail with a voltmeter set to low AC volts might be revealing if the rail is glitching/noisey.
C1476, is that it in your parts layout to the left of the number "89" arrow. If it is, it looks fairly skinny on the drawing you posted. What board is that on?
Which cap does he state has the lead arced open and on what board is that cap? A burnt/arced off lead sounds like a smoking gun.
PW
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TK,
Where is a video of the current state of this scope? Last one I saw was with severe blooming with what looked like horiz scan issues. Is there a newer video showing the scope functioning a bit better?
I think the blooming is just the intensity setting up too high. The scope produced a "perfect" image of the calibrator trace on CH1, but had some strange periodic glitch, like half a second interval, of a sharkfin-type trace that looked like it might be on the unblanked return of the beam.
Has Brian posted any DC measurements of at least the LV rails? 'Tis the best place to start.
No, not to my knowledge yet. I also have been asking for these, and I found in the manual which the testpoints are and the voltages/tolerances for them.
I doubt that tant is the only +5 rail decoupling cap, but if it is noisey, it might be glitching the line. Temporarily replacing it with an electrolytic or even just attaching one across the rail may assist diagnostics. In the absence of a scope for diagnostics, MH's suggestion of looking at the 5V rail with a voltmeter set to low AC volts might be revealing if the rail is glitching/noisey.
Yep.
C1476, is that it in your parts layout to the left of the number "89" arrow. If it is, it looks fairly skinny on the drawing you posted. What board is that on?
Which cap does he state has the lead arced open and on what board is that cap? A burnt/arced off lead sounds like a smoking gun.
PW
That is the one, C1476. It is on the A9 interface board. See the schematic excerpt below, from p. 228 in the pdf SM.
ETA: http://www.youtube.com/watch?v=C8WUWgIVG0A
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TK,
If it was me, besides already knowing the rail voltages, if I suspected the caps that are highlighted, I would temporarily replace them with something from my on hand parts bins. The two tants in question could be replaced with 47uf at anything over 10V electrolytics and that ,1uf ceramic with any ceramic of similar or greater uf and voltage rating should work OK as well (I think I would stay under .47uF). it would at least help identify if those are bad caps.
You say one channel actually shows the calibrator signal OK? I would think a problem with the highlighted caps would affect both channels.
Maybe you or Brian could post a link to the video of the calibrator signal. I thought things got worse after he cleaned the scope.
PW
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I wish I could just get a whole freakin' day to myself to sit here and test everything on this scope so I don't have to keep putting stuff away and taking it back out. Things would get done a whole lot faster.
Anyway, I should have the next couple hours at least free to do this....
I have 3 DMMs here and am going to check all the rail voltages.
I have used page 240 aka section 12 diagram as my reference for the test point to voltage matching.
Do you want me to also check all the rails on low V AC settings for "noise"? And this noise would be any unstable reading, correct?
I am going to do my best to record all of this procedure. I am first going to record a new vid of the calibrator trace from CH1 and CH2 separately and upload it, so we can get this rolling now that more people are interested.
Thanks for all the help everyone, and sorry it's been taking me so long to get the necessary info out here.
Brian
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I wish I could just get a whole freakin' day to myself to sit here and test everything on this scope so I don't have to keep putting stuff away and taking it back out. Things would get done a whole lot faster.
Anyway, I should have the next couple hours at least free to do this....
I have 3 DMMs here and am going to check all the rail voltages.
I have used page 240 aka section 12 diagram as my reference for the test point to voltage matching.
Do you want me to also check all the rails on low V AC settings for "noise"? And this noise would be any unstable reading, correct?
I am going to do my best to record all of this procedure. I am first going to record a new vid of the calibrator trace from CH1 and CH2 separately and upload it, so we can get this rolling now that more people are interested.
Thanks for all the help everyone, and sorry it's been taking me so long to get the necessary info out here.
Brian
Brian,
Please do check the supply rails and write down your measurements. When checking the DC rails with the voltmeter set to AC, anything over a few tens of millivolts is likely indicating a problem. You may have some noise pickup using unshielded test leads, but just get some rough DC and AC measurements for now (ideally, your AC readings will be close to zero). Pay particular attention to the 55 volt rail, it is used as the reference for four other supply regulators. Any noise or problems with that rail will affect the other four that use it as a reference. Since you've already had the scope on several times, I would not bother with the shutting down between measurements, unless it will take a significant amount of time or difficulty getting to the next measurement point. Consider using a clip lead to attach your meter negative lead to the supply common so you only need to probe with and concentrate on the other DVM lead. Be careful probing, don't slip and short something with the probe. If a TP is hard to get to, turn off the scope and use a spring hook or small clip lead to attach your meter to the scope. Happy hunting, look forward to your measurement results.
I am not sure I would bother making a video of you doing the supply measurements. If you use a tripod and having a camera on you does not make you nervous or distract you, go for it. But when working on the scope, you need to focus ONLY on working on the scope.
Can you provide a link to a video that most accurately reflects the current state of or problems the 'scope is having?
PW
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http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan1_zpsyc0entbh.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan2_zpshoyjanxs.jpg
Scans of A9 layout. They didn't turn out too great, but they seem better than the one you posted before.
I had to darken the contrast a bit to get the outlines, and it blurred some of the text.
PW -
here is a link to the most recent video. About to check it again and see if it's still the same and record that. Also I want to get a visual of channel 2 posted.
https://www.youtube.com/watch?v=C8WUWgIVG0A
Brian
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http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan1_zpsyc0entbh.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan2_zpshoyjanxs.jpg
Scans of A9 layout. They didn't turn out too great, but they seem better than the one you posted before.
I had to darken the contrast a bit to get the outlines, and it blurred some of the text.
PW -
here is a link to the most recent video. About to check it again and see if it's still the same and record that. Also I want to get a visual of channel 2 posted.
https://www.youtube.com/watch?v=C8WUWgIVG0A
Brian
Brian,
That video looks like the scope is mostly working. Does channel two function correctly? If not, what are its symptoms. Also, does selecting ALT or CHOP affect the channel one display adversely?
Do not attempt to measure the high voltage for now, you seem to have plenty of it. Just get some measurements of the low voltage supplies for now (from the 110 volt rail on down).
Is that extreme brightness/blooming just a camera artifact? I keep wanting to reach for the brightness control and turn it down!
PW
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https://www.youtube.com/watch?v=nMcNEvQ4b4o
Well it appears that everything is working perfectly now. I guess whatever was wrong was fixed when I removed the trigger/sweep boards and cleaned them up. There was a decent amount of gunk on the switch drums, so I'd imagine there was a good bit on the finger contacts as well. I couldn't get a good view of them, but I took a small camel hair brush and IPA and gently cleaned them by pushing the bristles in under the contacts back and forth, and turning the drum to the next setting and repeating. I also gently wiggled around the transistors and made sure they were fully seated.
Anyway, it must have been either a bad connection somewhere, or some dust or grime shorting something out or something along those lines.... cuz she works, and channel two works fine also.
I've had 'er sitting here running for the last ten min and everythings fine, so no heat problems either apparently. Should I even bother to check the rail voltages anyway?
The only thing I see is that there is a wee bit of a wave effect going on with the trace. Don't know if thats to be expected. Also, call me dumb but I don't know how to get both calibrator traces on the screen at the same time, unless they overlap on analog scopes instead of the shots I've seen of digital scopes where the top half shows one trace and the bottom another.
Either way I'm thrilled it's working and I don't have to replace anything. good thing I didn't order anything yet!! Plus, I got my new probes in the mail today, too!
Thanks for all the help!!! Now I get to learn all of the functions of it!
Brian
Ah.. figured it out. "CHOP" & "MIX" and then having them on two different V/div settings does the trick.
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Brian,
It sounds like you figured out how to display the two channels at the same time. Typically you will use ALT most of the time and CHOP for lower frequency signals.
Using your clip leads/wires, short each channels' BNC center contact to ground (BNC collar or the scope's ground lug) and with the channel gains turned up, switch between AC, DC, and GND on the input coupling switch. The trace should not move up or down while doing this. Any movement means there is offset in the input amp that needs calibration. Check the manual regarding this. You will likely need to switch your trigger source to LINE or switch to "free run" so that the trace appears with no signal applied.
As for the waviness, I assume this video was made with the scope covers on. If so, there is likely some supply ripple on one of the supplies. Your scope appears to be working sufficiently to use it to look at its own low voltage rails when you get a probe. Likely you have a little AC at line frequency riding on a rail, unless the video was made with the cover off. I have some scopes that will ripple a bit with the lid off.
Do you still get a weirdness when cranking on the trigger hold off?
Congrats, all in all it is looking pretty good.
PW
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yeah, the trigger holdoff is causing me some weirdness.
Uploading a vid of it now...
https://www.youtube.com/watch?v=-QnIyMVbbHE
Those type of pots that are right up against the faceplate I haven't cleaned at all. On all the other ones, of which were mostly noisy, I dripped a little Deoxit D5 on the shaft after cleaning the gunk/fuzz off, and worked them back and forth until the stuff got inside, then put another drop and repeated. did this with 2 or 3 drops on each pot and all of those seem to be working fine. Maybe I should start by doing that on the rest of these pots? Or do you think that it's most likely something else?
Oh, and the cover is off.
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Ok, I measured the voltage at the main power supply test points, and all the other ones. Had some interesting results on the Vertical preamp board....
(TP1518 +110V) 110.3VDC
(TP1536 +55V) 54.93VDC
(TP1548 +15V) 14.95VDC 1.34VAC
(TP1558 +5V) 4.999VDC
(TP1568 -8V) 7.97VDC
TP1486 17.77V
TP1590 10.74V 3.264VAC
TP1594 9.54V 2.008VAC
Vertical Preamp Board:
TP162 started at .6mV then climbed to 2.6mV then dropped back down to .2mV and kept going back and forth.
158.3mVAC
TP164 back and forth between 13.6mV and 14.2mV
162.9mVAC
TP346 back and forth between 23.6mV and 29.2mV
113.6mVAC
TP322 -29.7mV
back and forth between 1.463mVAC and 1.490mVAC
TP374 -1.175V
TP324 -66.4mV
46.2mVAC
TP364 -1.174V
TP262 back and forth between -18.8V and 19.8V
75.8mVAC
TP147 8.35V
TP141 8.37V
TP247 8.33V
TP241 8.33V
Is it possible that the AC riding on the +15V rail is causing all of this instability and AC on all these test points? seems like there is a good bit of AC running rampant in my scope. I'm gonna start inspecting the schematics to see if I can narrow down what component it could be. I'm sure you guys will be able to tell me exactly where to look, though.
Brian
Hmm, interesting. I adjusted the 55V adjust pot to EXACTLY 55V, and now there is absolutely no AC on the +15V rail. or any of the others.
I am going to go thru and check everything else for stability and AC now....
Some new numbers after the +55V rail adjust and disappearance of the AC on the +15V rail:
(A9 board)
TP1486 18.38V (the manual says that this is linked to the Intensity adjustment and varies from 0V to 75V)
TP1590 9.54V
3.268VAC
TP1594 10.76V
2.011VAC
TP1423 (-2450V rail) No AC. My meters max out at 1000V so I'm not checking the DC at that point. Wish I could.... maybe a X10, or even a X3 probe can be made for a DMM?? I don't see why not, but in order for it to be accurate I would have to use exact value components, and add in a tuning cap and maybe small VR? hmm..... could come in handy if it can be made......
(Vertical Preamp board)
TP162 3.3mV to 4.5mV
158.7mVAC
TP164 12mV to 8.8mV
163.3mVAC
TP346 -32.6mV to -25.6mV
114.7mVAC to 114.3mVAC (rapidly changing)
TP322 -32.2mV to -31.3mV
4.60mVAC
TP374 -1.178V
2.7mVAC to 4.4mVAC
TP324 -69.3mV
46.3mVAC
TP364 -1.177V
0mVAC to 1.4mVAC
TP262 -23.5mV to -24.5mV
76mV
TP147 8.37V
TP141 8.38V
TP247 8.35V
TP241 8.34V
The manual says that these are what the values of these test points should be
TP147 8.5V
TP162 0V
TP141 8.5V
TP241 8.4V
TP247 8.4V
TP262 0V
These two test points are in the Calibrator circuit. The values I am getting are way under the values that the manual shows I'm supposed to have...
(Page 234 of the Tek 465 manual linked to by TinselKoala on page 5 or 6?)
TP1590 10.8V
TP1594 54.7V
This circuit draws it's power from the 55V, 15V, and 5V rails, so if my values are off it must be one of the components in that circuit that is damaged, correct?
I am going to hook up to the closest ground and check to see if the values match the specified ones in exactly the places where the arrows are pointing to.
All of the rails appear to be doing great, especially now that I have gotten rid of the AC on the 15V. I have had it running for the last several hours non stop except for a couple of minutes and everything is good. Before I adjusted the 55V adjuster, I had adjusted the "A trigger Level" and "A trigger holdoff" to try and keep the trace steady constantly, but it still glitched a little from time to time. However after adjusting the 55V, it hasn't glitched a single time that I have noticed. :)
There are still definitely some issues to be worked out, though. I think here after I check a few spots for their specified voltages, I am going to pull the knobs on the A and B trigger level/slope and the A trigger holdoff and put a couple of drops of Deoxit on the shaft and let it sit, then work it around in the morning and maybe put one more drop in, too, just to "rinse" off any crud. I can't get the stuff out of there, so I can't be putting too much in, obviously.
I shall attempt to isolate all the other issues according to the manual as soon as I get a chance to tomorrow. I'm going to start finding deals on all the stuff listed in the "calibration" section that I will need for a performance check first of all, and then calibration. I will have to wait until I can pick up a good quality function gen that has all the functions I need in the tolerances I will need them in. I'm sure that won't be a problem. Oh, and a good Variac....
Brian
Ah, poop.... I'm going to have to redo all of that again tomorrow WITHOUT anything hooked to the input.................. ::)
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Brian,
Regarding the trigger holdoff, for repetitive signals such as the square wave from the calibrator, you will use the minimum holdoff setting of that control. Set it there and forget about it for now.
The trigger level control should be able to be set for stable triggering in both positive and negative going slope selection, AC, DC, HF reject, etc when looking at the calibrator.
Regarding the ripple disappearing when the 55V rail was adjusted. As per the manual, that rail was already within spec. Possibly the Vadjust control was noisey, but it is difficult to grasp how adjusting it cleaned up the ripple issue. When you get a probe, you can use the scope to look at the supplies for ripple.
Regarding the calibrator TP measurements, what is the level that you are seeing on the screen when connected to the input channels? I think it is supposed to be around 300 milivolts PP and if it is, move on. Keep in mind that the calibrator is typically used as only a fairly rough reference regarding amplitude and frequency. Its main function is to provide a fairly fast risetime signal to calibrate (adjust) the probe's compensation cap (when you get a probe).
Other than verifying the main supplies, as you have done, I would suggest using the scope or going thru the performance verification part of the manual to see what all is and is not working. A full calibration is going to require a few pieces of equipment you may not have. As well, it must be done in the order given in the manual, which typically begins with power supply rails.
You can do some DC measurements to verify the channel inputs are close. Use a 9V battery, connect it to an input channel, see what it reads using the scope and verify that voltage with your DVM. Repeat for other channel. This will give you at least an idea of where the preamp inputs are. You can repeat using a lower V battery to check accuracy at various voltages. Of course, if you have an adjustable DC supply, use that instead.
Don't start randomly tweaking cal trims in the scope unless you are setup to do the cal correctly with the required equipment. You may be able to do DC offset adjust and some other cals but I would use the scope a bit and see what is or is not working well.
Do you have a signal/function generator?
PW
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@Brian: To display both traces with signals from the calibrator, you don't need to use different V/div settings, you simply use the channel's Vertical Position control to put one trace on the upper part of the screen and the other trace on the bottom part of the screen. Set Vert Mode to "Alt" . Set the CH1 input coupling to "ground" to set the baseline on some graticule line in the upper part of the screen, then turn the channel input coupling back to "DC" or "AC" and scale the trace using the V/div control so it just spans a couple of vertical divisions. Do the same with CH2 except use some graticule line on the lower part of the screen for the "ground" or zero volts baseline. Then you'll have two traces that don't overlap (unless you scale them to do so using the V/div control) and since both will have the same setting on the V/div control you can compare their amplitudes, which should be the same . (Red "var" knob on the V/div controls fully CW and in the detent.)
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yeah, the trigger holdoff is causing me some weirdness.
Uploading a vid of it now...
https://www.youtube.com/watch?v=-QnIyMVbbHE (https://www.youtube.com/watch?v=-QnIyMVbbHE)
Those type of pots that are right up against the faceplate I haven't cleaned at all. On all the other ones, of which were mostly noisy, I dripped a little Deoxit D5 on the shaft after cleaning the gunk/fuzz off, and worked them back and forth until the stuff got inside, then put another drop and repeated. did this with 2 or 3 drops on each pot and all of those seem to be working fine. Maybe I should start by doing that on the rest of these pots? Or do you think that it's most likely something else?
Oh, and the cover is off.
OK< I see that you have figured out how to show both traces properly separated using the vert position controls. It doesn't look "weird" to me now. I think the issue you are seeing now has to do with the trigger _level_ setting rather than the trigger holdoff. For this signal turn trigger holdoff to the "norm" position and leave it there.
Make sure Trigger Source is on CH1 or CH2, mode is AUTO and adjust A Trigger Level for a stable display. Horiz Display on "A".
Try turning the horizontal timebase to a faster setting so you are only displaying three or four cycles of the waveform on the screen. This will help with some diagnostics, now that you are getting traces there is no need to keep the scope in the 1 ms/div setting.
Anyhow, it does look much better now, perhaps your cleaning did indeed fix it! Or maybe it just likes running on its side. ;)
Running a full calibration is probably overkill. It would be nice if you could use some different input signals, like from your GenRad oscillator, for some higher-frequency testing.
It is likely that the little ripple you are seeing is due to the casual grounding we have been using for the input signals, or perhaps some ripple on a power supply due to a faulty capacitor.
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On testing the HV supply: Don't bother! This has to do with the display itself and that seems to be working just fine. If you didn't have a trace, or trace too dim, or improper blanking or something like that, then that's the time to worry about the HV supply. It's just too tricky to mess with that unless you actually suspect some problem and I don't think you have any reason to suspect a problem in the HV circuitry at this point.
Also, in regards to the calibration.... again... you are looking at "overkill" here. The equipment necessary to do a full and proper calibration is going to be expensive, and you'd be better off spending that money on something else that you'll use all the time. Who needs a time marker generator or a calibrator generator or a signal pick-off unit for anything, except a bench technician who spends all day every day calibrating old analog scopes? Plus you need another scope to do a full calibration anyway.
You can look for a good modern full-function Function Generator, and do most of the performance verification and much of the calibration checks with that. Plus your GenRad oscillator for higher frequencies. And a Variac is always handy around the lab. These, some patch cables, adapters and a 50 ohm terminator, are enough.
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I found these chips:
http://www.analog.com/media/en/technical-documentation/data-sheets/AD9837.PDF (http://www.analog.com/media/en/technical-documentation/data-sheets/AD9837.PDF)
http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9833.html#product-overview (http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9833.html#product-overview)
Cheap:
http://www.digikey.ca/product-detail/en/AD9837ACPZ-RL7/AD9837ACPZ-RL7TR-ND/2677471 (http://www.digikey.ca/product-detail/en/AD9837ACPZ-RL7/AD9837ACPZ-RL7TR-ND/2677471)
•Digitally Programmable Frequency and Phase
•12.65 mW Power Consumption at 3 V
•0 MHz to 12.5 MHz Output Frequency Range
•28-Bit Resolution (0.1 Hz @ 25 MHz Ref Clock)
•Sinusoidal/Triangular/Square Wave Outputs
•2.3 V to 5.5 V Power Supply
•No External Components Required
•3-Wire SPI Interface
Another virtual project in a box: You buy a tiny Arduino board with a VGA out and a USB port for your mouse. You run Linux for the GUI and write a small program to poke the registers of the oscillator chip. With two small isolation transformers and three wall warts you can get a "floating set" of +5, -15, and +15 volts. You buffer the output of the oscillator chip with an op-amp. You have analog gain and offset knobs. You have direct out and 50-ohm out. You can even do the high-current transistor out if you want using a pair of external batteries as the power source.
A small box that you plug in the wall, and there are a few BNC panel-mount connectors on the box, and you use an old VGA monitor and mouse lying around. You "cheat" and there is just a neatly wired breadboard inside the box along with the Arduino module.
I know I am so out of date, perhaps there is a module that does that all for you. But then you miss out on the fun of making it!
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eBay has lots of function generators and kits built around DDS chips, some for under $20. Pirate Bill asked about using one. Complete and in a box you can buy one that does 5 MHz or 10 MHz for around $70.
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I found these chips:
http://www.analog.com/media/en/technical-documentation/data-sheets/AD9837.PDF (http://www.analog.com/media/en/technical-documentation/data-sheets/AD9837.PDF)
http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9833.html#product-overview (http://www.analog.com/en/products/rf-microwave/direct-digital-synthesis-modulators/ad9833.html#product-overview)
Cheap:
http://www.digikey.ca/product-detail/en/AD9837ACPZ-RL7/AD9837ACPZ-RL7TR-ND/2677471 (http://www.digikey.ca/product-detail/en/AD9837ACPZ-RL7/AD9837ACPZ-RL7TR-ND/2677471)
•Digitally Programmable Frequency and Phase
•12.65 mW Power Consumption at 3 V
•0 MHz to 12.5 MHz Output Frequency Range
•28-Bit Resolution (0.1 Hz @ 25 MHz Ref Clock)
•Sinusoidal/Triangular/Square Wave Outputs
•2.3 V to 5.5 V Power Supply
•No External Components Required
•3-Wire SPI Interface
Another virtual project in a box: You buy a tiny Arduino board with a VGA out and a USB port for your mouse. You run Linux for the GUI and write a small program to poke the registers of the oscillator chip. With two small isolation transformers and three wall warts you can get a "floating set" of +5, -15, and +15 volts. You buffer the output of the oscillator chip with an op-amp. You have analog gain and offset knobs. You have direct out and 50-ohm out. You can even do the high-current transistor out if you want using a pair of external batteries as the power source.
A small box that you plug in the wall, and there are a few BNC panel-mount connectors on the box, and you use an old VGA monitor and mouse lying around. You "cheat" and there is just a neatly wired breadboard inside the box along with the Arduino module.
I know I am so out of date, perhaps there is a module that does that all for you. But then you miss out on the fun of making it!
Hells yeah, man!
That's pretty awesome you found that... I might just have to order a couple when I do place an order. I know I could just buy a cheap Chinese $20 function gen, but I need the experience learning how to design and build circuits, and learn how to write code for Arduino, so that would be a great project for me to get into. With the help of progs like ExpressPCB and SCH and a good simulator, and referencing schematics for function gens, I'm sure I could get it figured out. Plus I have the Arduino - the Mega 2560, Yun, and one of those little bits kits to play with. Might be something good to use one of my old laptops for, since it takes practically nothing to run Linux.
Who knows though, maybe I'll end up buying a good high quality function gen before I get it finished...... That's a lot of stuff to learn, but I'm def up for the challenge - once I've got this scope thing down.
Well, time to hook up the scope and get going on the stuff that has been suggested I do by TK and PW.... that is, until I have to go grocery shopping. It seems like time just flies by... where's that fancy remote that slows everything but you down????
Brian
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MileHigh,
What you think of using this to build a function gen around?
http://parts.arrow.com/item/detail/arrow-development-tools/bemicromax10#2FFJ
Brian
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Brian:
I only know very little about what's out there.
The software tools, feature set of the board and price are your three main considerations. That board looks like an FPGA along with a CPU. That's pretty amazing but you don't need the FPGA. I am not sure what hardware and software features you want. Then just shop around to find a board with all or most of your features. The brand or the architecture of the CPU are really irrelevant here. Jut get something mainstream. This app requires no real processing power.
I am pretty sure the SPI interface can be done with a few I/O pins and a readily available library, you should check that. It looks like writing your own SPI interface driver would be pretty easy also but it has to exist already.
MileHigh
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Here is an interesting Plan B:
You don't even buy a microcontroller board. You do all of the software for the frequency generator register poking and the GUI on your PC and you get a USB to SPI dongle.
http://www.cypress.com/?rID=57207 (http://www.cypress.com/?rID=57207)
Then the external box just has the waveform generator chip, the power supplies, and the support electronics, etc.
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Here is an interesting Plan B:
You don't even buy a microcontroller board. You do all of the software for the frequency generator register poking and the GUI on your PC and you get a USB to SPI dongle.
http://www.cypress.com/?rID=57207 (http://www.cypress.com/?rID=57207)
Then the external box just has the waveform generator chip, the power supplies, and the support electronics, etc.
First the development board that Brian found is for an FPGA. There is not a hardware uC on board. Any uC would be soft in the modest sized FPGA. A uC is useful for things like a front panel display. So the USB to I2C dongle is a better way to go. If there were enough interest we could kick around an open source design for a USB based function generator with really nice capability, like +/-20Vpp output drive.
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MileHigh:
I know that I won't need an FPGA for the function gen project, but I was just thinking that might be a nice to have dev board for a large variety of projects. But now that I'm fully rested and awake, I think I would likely dedicate whatever is used to the FG, so you're right, it's pretty pointless to get for this project. Maybe later on down the road when/if I find something I would need the FPGA for. Plus I see now that it doesn't have I2C or SPI, either.
I don't see a price for the DG USB to SPI/I2C dongle on that page. Maybe one has to contact them to find out.. It's obv from Germany so maybe shipping would be more then the device itself, but still should be fairly cheap anyway. Either way, it would be a great tool to have.
I was poking around the other day and found a schematic and instructions for building an easy USB to I2C dongle that I'm sure could be adapted for SPI. I couldn't find the link right off hand, but I'm pretty sure I saved the page in a folder and will find and add it once I do.
Speaking of PC based, Check this out:
http://hackaday.com/2014/10/22/function-generator-with-zero-cpu-cycles/
It says it was only used for 200khz, but maybe there is a similar chip to the PIC32 that can get us to the Mhz range? They don't really give enough info on it so I'll have to dig around for more info. Chances are, this is specifically around the PIC32 chip and doesn't work with any that will get us in the Mhz range, but it's an interesting article/idea anyway. Good to know about if someone ever needs a quick, clean sine wave up to 200khz if nothing else.
I don't know if it was just my PC/connection, but for most of the day yesterday this site was almost completely unavailable as if there were some major server issues. Anyone else have that problem? If not I'm going to have to do some PC cleaning........ I need to put a partition on here and put Linux on it anyway.
Brian
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The PIC scheme is a poor match to a DDS chip. The PIC scheme can only output values at integer divisions of the DMA clock. DDS performs M/N*FCLOCK frequency synthesis. Up to the resolution of the internal numeric represetnations, you can get pretty much any frequency that you want.
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So what DDS chip would you recommend? I've read a good bit that more or less said that the best ones to go with are the AD series, particularly AD9914. Also the 5932, 9833, and 9959... oh, and also the XR2206. What are your thoughts, MarkE?
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Brian,
Your decision regarding what to buy as a signal source is somewhat dependent upon what you want to use your test equipment for.
That said, I'd recommend saving up for a good used FG or buying one of the 2MHz units on Ebay for $60 or so.
For now, if you're just learning to use a 'scope, I would suggest playing with some audio sources. Simultaneously listening to music while viewing it on your scope gives you a good visualization of what is going on with both. Although music/audio signals are a bit more complex (and harder to trigger on) than what is produced by an FG, displaying a left/right stereo signal on your scope while listening to your favorite music can be both enjoyable and enlightening with regard to your scope's operation.
Also, there is sound card FG software out there. Possibly someone here can recommend a freeware (and a clean download link) that can get you started in that direction.
Even with a FG (or FG software), I would recommend adapting the signal cables as necessary to allow you to listen along as you view various waveforms and frequencies on your scope.
PW
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You can use the powerful audio editing applications Audacity (linux) or GoldWave (windows) to generate all kinds of audio frequency waveforms to look at, output from your computer's sound card, one or two channels as you like.
Audacity is freeware and so are versions of GoldWave.
And don't forget about the venerable GenRad 1330-A, which covers the RF range from 5 kHz to 50 MHz with a sine wave output that can also be partially modulated by the fixed audio frequencies from the unit's audio oscillator section ( at the higher frequency ranges of the RF signal).
If I had a hundred dollars to spend I'd buy this right now:
http://www.ebay.com/itm/Interstate-IFC-F-74-F74-20Mhz-Sweep-Function-Generator-/301529989757 (http://www.ebay.com/itm/Interstate-IFC-F-74-F74-20Mhz-Sweep-Function-Generator-/301529989757)
Note the back panel Signal Ground isolation switch... this can be a very helpful thing to have in a function generator.
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Also, there is sound card FG software out there. Possibly someone here can recommend a freeware (and a clean download link) that can get you started in that direction.
I recommend this PC based O'scope and sig gen combo software for the beginner.
Many features including sweeps of audio, spectrum, etc
http://www.zeitnitz.eu/scope_en (http://www.zeitnitz.eu/scope_en)
There are other good ones out there, I just happen to like this one.
Do build a limiter protection box for your soundcard.
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I recommend this PC based O'scope and sig gen combo software for the beginner.
Many features including sweeps of audio, spectrum, etc
http://www.zeitnitz.eu/scope_en (http://www.zeitnitz.eu/scope_en)
There are other good ones out there, I just happen to like this one.
Do build a limiter protection box for your soundcard.
Are you using a sound-card based oscilloscope for your waveforms that you posted earlier? I have encountered several cases where PC-soundcards actually inverted one or both of the inputs when used with scope software, with no indication other than the flipped phase of the displayed signals themselves.
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So what DDS chip would you recommend? I've read a good bit that more or less said that the best ones to go with are the AD series, particularly AD9914. Also the 5932, 9833, and 9959... oh, and also the XR2206. What are your thoughts, MarkE?
I f I were going to build something I like the AD9857 because it is 14 bits. But there is lots of stuff that you can buy that is cheaper than the one chip alone. $20. gets you something like Pirate Bill found and $60. gets you something that is packaged in a half way decent case that does 5MHz.
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That said, I'd recommend saving up for a good used FG or buying one of the 2MHz units on Ebay for $60 or so.
PW,
That goes right along with what I was just thinking about asking - If, being at the stage I am at, it would be reasonable to buy a DDS chip and build a FG, and if I would be able to obtain comparable features and same or better signal quality. Sometimes when I think of something, I immediately dive in the deep end as far as ideas/plans go, and then as a few hours or so goes by, I think a little more into whether I'm being reasonable or not. Most of the time, it's not.
You can use the powerful audio editing applications Audacity (linux) or GoldWave (windows) to generate all kinds of audio frequency waveforms to look at, output from your computer's sound card, one or two channels as you like.
Audacity is freeware and so are versions of GoldWave.
And don't forget about the venerable GenRad 1330-A, which covers the RF range from 5 kHz to 50 MHz with a sine wave output that can also be partially modulated by the fixed audio frequencies from the unit's audio oscillator section ( at the higher frequency ranges of the RF signal).
If I had a hundred dollars to spend I'd buy this right now:
http://www.ebay.com/itm/Interstate-IFC-F-74-F74-20Mhz-Sweep-Function-Generator-/301529989757
I'll have to go to storage and dig out my old Dell dimension 8250 and get it up and running with Linux, and download some software on it. I don't feel like buying any cheap-o USB sound cards, and I have 4 or 5 good 5.1 sound cards in storage I can use. I did read up on sound card based FG's a little bit, and got the jist that I will most definitely be needing to build a limiter unit so I don't fry them up crispy. I don't know if that PC will support installing more than one sound card, but it would be pretty nifty if I could install two, run a PC scope on one, and FG on the other, or have several FG/scope channels. I know I already have a real scope and everything, but there should be some math/charting features along with other digital scope features on the PC based scope. But instead of using a cheap 3.5mm home-made probe for it, maybe I can build a little BNC interface box - or if I can get that dongle, maybe I can make something with that. or even the arduino. I'm probably getting a little bit ahead of myself here though. Just some ideas.
I'll just start with the sound card FG, though.
Hopefully some of my stuff on ebay sells soon, and then maybe I can scoop up that FG you linked to before it's gone...
I recommend this PC based O'scope and sig gen combo software for the beginner.
Many features including sweeps of audio, spectrum, etc
http://www.zeitnitz.eu/scope_en
There are other good ones out there, I just happen to like this one.
Do build a limiter protection box for your soundcard.
Vortex -
That definitely seems like a good one to start with once I get my desktop out of storage. I'm running out of room to put all of this stuff! Going to have to do some re-organizing and add some more shelves to my ikea wall unit...
Brian
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Brian,
Why would you need a dedicated computer or two sound cards to start using a software based FG and your scope?
What are you posting on this forum with?
PW
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Brian,
Why would you need a dedicated computer or two sound cards to start using a software based FG and your scope?
What are you posting on this forum with?
PW
My laptop, and as far as sound card goes, all it has is a combo jack. Now that you've asked...
What is the real difference between using FG software out the headphone jack to a modified cable and a FG off of a dedicated sound card?
Is it really only the PC based scope that needs a dedicated sound card?? I'm confused. going to have to do a search and read a few articles again..
I have FG software. There is an FG built into Visual Analyzer, and "Function Generator" by Cognaxon. From what I remember, the only issue with using PC based FG's is the amplification. Is this correct? (That is, amplification for using the FG for more than just running it to the scope, I'm sure using it without amplification is fine for only that aspect. Maybe this is where I am confusing people.....)
I may have confused some of you when speaking of this, because I was referring to having a PC based FG and possibly scope w/ extras for future projects as well. Sorry.... I need to just stick to talking about specifically using it for learning functions on the scope. My fault...
Brian
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Ok, so what I have done here is this:
I have a standard 3.5mm stereo audio cable ran to a jack that I pulled off a board. I figured out what was left, right, and ground, and soldered red, white, black to it. I'm about to connect another jack into the setup so I can listen in to the signal.
Do I need to be on AC or DC? This is what I am unsure of as far as when I connect to something... what qualifies for an AC signal and what qualifies as DC? and what do I use ground for? Is that ground setting also to be referred to as "reference"? meaning that, on that setting, I would be seeing what my AC or DC signal would be in reference to?
Also, I would only need a limiter protection box if I were running my signal to an amp and/or using it for anything other than putting the signal to the scope, right?
Brian
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That little switch under the channel vertical V/div setting knob is the most misunderstood scope control ever, and is a particular "pet peeve" of mine.
This is the channel's _input coupling_ switch.
AC -Ground-DC.
It does NOT refer to the "type of signal" that you are measuring! It refers to how the signal is _coupled_ into the oscilloscope.
The "ground" setting is, or should be, obvious. It disconnects the probe _tip_ from the scope and connects the input circuitry directly to the scope's chassis ground. This means that the scope's input sees "zero volts". No signal. So you select this when you want to set the channel's baseline, or zero voltage display, on some reference marker on the screen, like the center graticule line or some other graticule line of your choosing using the vertical position control. It essentially turns that channel's input off, removes the signal from the probe, connects the scope's input to ground (and leaves the probe tip floating so it doesn't short-circuit the device under test.)
The "DC" setting is called "DC Coupling". I believe it should more properly just be called "Direct Coupling", since that is what it does: It connects the probe tip _directly_ to the scope's input circuitry. Just that. (Here I'm disregarding the input and probe impedances or 10x voltage divider, which are irrelevant to this discussion.)
The "AC" setting is the one that causes confusion. This is "AC Coupling".... the switch simply puts a capacitor in series with the scope probe tip. Just that. This is a "high pass filter" arrangement that works to filter out, or eliminate, a DC component to the signal (the very slowly changing or unchanging part) and only allows the rapidly changing part of the signal to pass through to the scope's input circuitry.
The "AC coupled" setting has two major effects on what you see on the screen.
First, it removes the DC component of an oscillating signal. So, if you are interested in seeing the small oscillating ripple riding on top of a larger DC signal.... this is what you would use to view it. For example, say you have a ripple of 20 mV sitting on top of your +55 V DC power supply. How do you display such a thing? If Direct Coupled, and you use a V/div value that keeps the 55 V on the screen, the ripple is so small compared to that, you'll never see it accurately. So you need to _remove_ that +55 volts DC from the signal and magnify the 20mV ripple so that you can see it displayed at sufficient resolution to measure it. You select "AC Coupled", and then you can turn the V/div setting to some low value like 10mV/div and the ripple will be displayed rippling around the zero baseline level (that you positioned with the "ground" setting) at a good magnification. So in this case even though you are looking at a mostly DC signal, the AC-coupled setting is the appropriate one to use to view the ripple. You use DC-coupled to see the overall voltage level, and AC-coupled to see the tiny ripple on top.
Second, the AC-coupled setting takes the _average_ of the displayed signal and moves it up or down to the channel's zero baseline level that you set using the "ground" switch setting and the vertical position control. Obviously, you then lose the absolute voltage values of the signal when this happens. Peak-to-Peak value remains the same and is accurate, but you no longer know what the actual _peak_ values are because the trace has been moved down or up by some unknown amount to place the _average_ on the zero baseline. So even if you are measuring a truly "AC" signal, if it is not symmetrical about the zero value, the scope will make it _look_ like it is, and sometimes this will be false.
All scopes, whether the latest digital one with all bells and whistles, or an ancient analog clunker, accomplish this miracle in the same way: they simply place a capacitor in series with the probe when "AC-coupled" is selected. Analog scopes do this with a simple switch, digital ones use a software-controlled relay.
Most of the time you will use the DC-coupled setting for almost everything you do with the scope, whether measuring "AC" or "DC" signals. The most often-used reason for using the AC-coupled setting is what I mentioned above: Viewing small ripples on top of larger DC offset signals.
That Interstate F74 sweep FG that I linked earlier is a _good buy_ at 100 dollars. It has functionality that you will not find on many modern FGs for three or four times the price. 20 MHz range, a relatively fast pulse generator feature, a high-amplitude output, the sweep function, ability to float the signal ground, etc. The only drawback to these old Interstate models is the frequency setting knob. It is a vernier control, but it is still a little hard to set a precise frequency on it. I generally run my F43 into a hardware frequency counter when I need to set a precise frequency and this pretty much solves that problem. It is also kind of hard to find manuals for the Interstate line. But they are constructed with the same "generation" of technology as your 465 scope: mostly discrete components, only a few ICs on a robust double-sided circuit board with plenty of room to work.
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No separate soundcard is needed. Just use the existing soundcard in the pc.
Stereo line or headphone out is the 2 channel FG output. Stereo line in is the 2 channel scope input.
This applies to the PC based scope I referenced earlier.
I don't know if this software supports a separate dedicated soundcard. A manual is available, it mjght address that issue.
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Ok, so what I have done here is this:
I have a standard 3.5mm stereo audio cable ran to a jack that I pulled off a board. I figured out what was left, right, and ground, and soldered red, white, black to it. I'm about to connect another jack into the setup so I can listen in to the signal.
Do I need to be on AC or DC? This is what I am unsure of as far as when I connect to something... what qualifies for an AC signal and what qualifies as DC? and what do I use ground for? Is that ground setting also to be referred to as "reference"? meaning that, on that setting, I would be seeing what my AC or DC signal would be in reference to?
Also, I would only need a limiter protection box if I were running my signal to an amp and/or using it for anything other than putting the signal to the scope, right?
Brian
AC coupling inserts a series capacitor between the signal that you are measuring and the vertical amplifier. This applies a controlled amount of distortion to the measured signal that:
Removes all DC information.
Attenuates AC information in varying degrees as the frequency falls below about 1/(CCOUPLING*1E6) or typically about 1% attenuation at 40Hz, and shifts the phase of the measured signal beginning below about 40Hz.
AC coupling is useful when: There is a large and stable DC offset on a signal, and there is little or no content between DC and at least ~40Hz or higher. For example: If you want to see the ripple on top of a power supply rail, then AC coupling lets you crank up the gain and see that ripple.
AC coupling is of course useless for DC signals, or signals where the DC content matters (power measurements for instance), or where there is signal content that matters between DC and ~40Hz.
Scope settings for novices:
Probe set to 10X.
Input set to DC.
Gain set to display the entire signal on the display, including the extent of any spikes.
Persistance set to OFF
Averaging set to OFF
20MHz filter set to OFF
Trigger mode set to AUTO
Trigger coupling set to DC
Trigger level autoset to 50% once signal is connected(Tektronix scope feature, may not be available on other brands)
Trigger position set to 0 (Tektronix scope feature, may not be available on other brands)
Change trigger mode from AUTO to NORMAL
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TK, MarkE,
Thanks for the clarification. I am going to mentally tag them "Direct" and "Average" so as to remember that DC is for Directly measuring the actual signal, and AC zeroes out the Average signal in order to show the ripple.
This is all starting to come together and make sense to me now. I'll know how to use this scope in almost no time at all! :) It even seems like a good place to start with scopes in general, since the digital ones have sooo many more functions I will need to learn when I one day scoop one up. This one will do just fine for quite a while.
Vortex,
Thanks for pointing me to that program. Seems like a decent all around FG/scope when it comes to free stuff. I have a mono mic input on my combo jack so I would only be able to use 1 channel, but for now I'll only be using the FG part since I already have this 465 to figure out.
I would also just like to note that putting the case back on the scope made a HUGE difference on the stability of the trace and functionality of the controls. I would never have imagined that something as simple as that would have such a big impact. They really designed these scopes down to the tiniest detail, didn't they??
Brian
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Went to check the compensation on the new probes and the old probes, and noticed that the waveform I am seeing differs a little from the one depicted in the old scope manuals. Just want to make sure that is what it should look like, so I uploaded another vid. I went thru various settings with the direct lines still hooked up to get the hang of things, and am now checking the probes and then putting some signals from the FG into it to see what I get. Getting pretty tired so I'll probably save a bit of the good stuff for tomorrow.
I noticed a little issue on the ALT setting with it not wanting to show the CH1 waveform in it's full width on the top section of the screen, and did the same with CH2 on top, and it seemed that adjusting the B trigger level made it a little better. I decided that I would try it again with the probes instead of direct links and see what happens. If I'm still having issues with it and can't figure it out tomorrow, I'll shoot another vid to show you all what's going on. Hopefully it's nothing, though.
https://www.youtube.com/watch?v=FDZ2ZhdMle4
Brian
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Yes, that calibrator trace does look a little funky. It should be more level across the tops and bottoms. I presume you have adjusted the probes for the squarest-flattest possible display as per the instructions. Did you say at one point that you found some voltages that were off-spec in the calibrator circuit? The spec on the calibrator output is 300 mV plus or minus one percent at normal temperatures. So this should produce a flat, horizontal top and bottom parts of the square wave output. It looks like the output voltage is sagging a bit in the pulses, or at least the display of them is. Now is when you'd like to have a good external square wave generator, and/or another scope, to see if the problem is in the calibrator or somewhere else in the scope! If the "known good" square wave generator gives you a good flat-topped trace then you know that it is the calibrator sagging, but the scope itself is displaying correctly.
As to the voltage asymmetry: Since you are in AC-coupled input mode I would expect the displayed trace to be more symmetrical about the zero-baseline even if the calibrator signal itself isn't perfectly symmetrical. This may be a "DC bias" issue, which is an internal adjustment that you will come across when you run through the performance checks or calibration procedures. Again, it would be nice to see what happens when you display other signals that are known not to have any DC offset. Have you tried looking at the GenRad oscillator's sine wave output yet? If that instrument is working properly it should be giving a symmetrical sine wave.
I don't know if you have the short "operator's manual" in addition to your SM. I'm attaching it below just in case you don't have it. It has lots of instructions for making the various measurements that are possible with the scope. (It also includes instructions for the DMM option which you don't have, obviously.)
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Ah.... do you have the probes in 1x or 10x attenuation? I just noticed that my Tek 2213a does the same thing if I have the probes set to 1x instead of 10x and only when AC-coupled. When DC-coupled the traces flatten out nicely. The cal trace slopes in exactly the same way yours is doing when I use 1x probe atten and AC coupling.
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OK, I've made a short video that I think accounts for both issues: the sloping trace and the voltage asymmetry. At least it accounts for those symptoms on my Tek 2213a, and I think that the same thing is going on with the 465 as well.
My Tek 2213a shows the same thing when the probe is set to 1x attenuation and the channel is AC-coupled. Also,when the probe is set to 1x, the compensation capacitor adjustment has almost no effect on the shape of the trace. When set to 10x attenuation the probe compensation can be adjusted as per the instructions in the probe manual.
When DC-coupling is selected with 1x attenuation, the sloping of the calibrator trace goes away. When the probe is set to 10x attenuation, there is no sloping in either AC or DC coupled input.
The voltage asymmetry around the zero volt baseline when AC-Coupled is due, _I think_, to the slight time asymmetry, or duty cycle, of the calibrator signal. Since the AC coupling brings the average of the trace down to the zero baseline, it is the _areas_ of the positive and negative going parts of the "square" waveform that are averaged. The narrower (shorter duration) part of the pulse waveform will have a slightly higher peak value than the wider part.
http://www.youtube.com/watch?v=HmHRdh8OnUw
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Ah.... do you have the probes in 1x or 10x attenuation? I just noticed that my Tek 2213a does the same thing if I have the probes set to 1x instead of 10x and only when AC-coupled. When DC-coupled the traces flatten out nicely. The cal trace slopes in exactly the same way yours is doing when I use 1x probe atten and AC coupling.
Yes, I did have the probes on 1X attenuation.
OK, I've made a short video that I think accounts for both issues: the sloping trace and the voltage asymmetry. At least it accounts for those symptoms on my Tek 2213a, and I think that the same thing is going on with the 465 as well.
My Tek 2213a shows the same thing when the probe is set to 1x attenuation and the channel is AC-coupled. Also,when the probe is set to 1x, the compensation capacitor adjustment has almost no effect on the shape of the trace. When set to 10x attenuation the probe compensation can be adjusted as per the instructions in the probe manual.
When DC-coupling is selected with 1x attenuation, the sloping of the calibrator trace goes away. When the probe is set to 10x attenuation, there is no sloping in either AC or DC coupled input.
The voltage asymmetry around the zero volt baseline when AC-Coupled is due, _I think_, to the slight time asymmetry, or duty cycle, of the calibrator signal. Since the AC coupling brings the average of the trace down to the zero baseline, it is the _areas_ of the positive and negative going parts of the "square" waveform that are averaged. The narrower (shorter duration) part of the pulse waveform will have a slightly higher peak value than the wider part.
http://www.youtube.com/watch?v=HmHRdh8OnUw
The 465 acts exactly the same as your 2213A in these aspects.
Definitely very helpful information. Not even the scope manual nor the probe manuals from Tek specified anything at all about them having to be on 10x and DC coupling in order to properly adjust the compensation cap.
One issue I have noticed with these Chinese probes is that the scope does not automatically detect whether I have it set on 1X or 10X. I seriously doubt it, but are all these fairly cheap Chinese probes this way? If not, I would have to say that I do not recommend them to anyone. These ones are the model "PP-200", although the seller's listing did not specify this at all. If I would have bothered to ask them, I'm sure they would have had no choice but to tell me. They said that they have never had any returns, though, and they have 100% feedback and all that jazz. Seems that really doesn't mean all that much these days. Do you think that possibly the reason why it doesn't recognize the attenuation setting on these cheap probes is because it is so old?
Is there any way for me to manually change what attenuation the scope shows, so I can match the display to the probes? I don't really know if this is particularly necessary, since the screen shows exactly the same trace with the cheap ones as it does with the 6062A and 6065A. The only real difference is that the indicator light at the V/DIV knob doesn't change.
There does seem to be a few other quirks with this scope as far as what the screen shows when the settings are not set for the trace to appear entirely on-screen. At this point, I'm not too concerned about it since, well, who really would want any part of their trace to appear off screen??? And maybe in time after some use, the rest of whatever gunk/oxidation remains inside of the pots and switches will work itself loose with the deoxit that is in there still. If not, here in a few weeks maybe I'll put a drop of WD40 or PB in each one and let 'er sit for a few days and see where it stands then. (of course after I try putting some deoxit and WD/PB in an old pot I have laying around and testing it several times to make sure it doesn't cause any issues/shorts/etc)
Anyway, what are your thoughts on the attenuation sensing w cheap probes issue? Just keep it in mind and keep on rollin along the knowledge superhighway?
Brian
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Ok, so it appears that I still have a fair amount of "noise" and bad contacts on channel 2.
-I did a quick test with an old pot similar to the ones used in the scope:
-I hooked it up to my DMM on the Resistance setting, and observed how smoothly/roughly it functioned without any treatment. It was OK, but not all that great. It had quite a fair amount of 'noise', meaning that the R value would jump around a bit while adjusting, instead of smoothly increasing or decreasing.
-I left it connected, and put a couple drops of Deoxit on the shaft and let it seep in for a minute, then slowly adjusted and observed. This created a good bit of "extra noise" in the pot, and what I mean by this is that, when adjusting the pot, the resistance would 'jump' up to 2x or even 3x of the overall R value of the pot. It would immediately settle to where it should be upon stopping rotation.
-I let it sit for a couple minutes and repeated, with close to the same results, but a little less 'jumping'.
-I then put a single drop of PB blaster on the shaft and let it seep in. Waited a couple min, then repeated the adjusting/observing process. It continued to do the same thing ('jumping' effect) but a little less frequently.
-After sitting for approx 10 minutes, still connected and DMM powered on, while adjusting the pot I get absolutely no 'jumping' and the pot works almost flawlessly, and much, much better than it did before any treatment. Another 10 minutes, and I am noticing that it is jumping again, but only by about 300 ohms, and only occasionally. It seems to be occurring in about the same positions, though, which I would think might be grime that has settled on the contact surface after the PB has ran off.
I am going to set this pot aside and see how it performs later, check for any shorting, "noise", etc. I am also going to take a similar pot and do the same but without the PB Blaster. Then after several hours or so I am going to rinse them out with IPA and see if their performance changes.
I am thinking that, since I still have a fair amount of 'noise' in some of the pots on my scope, I may take the cover and the knobs off and put a drop or two of PB Blaster in them, work it in by turning, let it sit overnight, and then rinse them all out with IPA twice and let them dry out before I power it up again, and see if it's any better. I just don't think the Deoxit is up to the task in it's entirety (of course I will find out for sure if I can find another old pot that is close to the same as the one I just tested). Not to mention it's only D5, not the PowerBooster stuff that is actually a cleaner instead of mostly conditioner. Plus I think it would be smart to rinse out the cleaner and loose gunk, anyway. Hopefully that FINALLY solves the rest of my "noise" issues once and for all!!!
Oh, and for everyone who might not know, PB Blaster is the pro-grade equivalent of WD40. PB = "Penetrating Blaster". It's somehow also made to attract to rust and ferrous metals so it will free up heavily rusted and/or stuck parts. Just a little heads-up in case some of you end up being in need of something like that when your WD40 can't handle the task.
If, after the overnight PB/IPA rinse treatment, she's still got issues with CH2, I will make a vid showing what's happening. I just wish I had a tripod so I don't give you all nausea having to watch my shaky vids....
Brian
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OK, so we have the issues relating to the calibration trace sorted, then, I hope. Nothing is wrong, it's normal behaviour when looking at the Calibrator signal with a 1x probe and AC-coupled input. The probe compensation should be adjusted with the probe in the 10x position, and normally you will be using 10x probe setting and DC-coupled inputs in most cases anyway.
You do realize that you will void your factory warranty by using that "blaster" stuff on your scope, I hope.... ;)
Seriously... I don't think that any form of petroleum solvent is a good idea to use. Who knows what kind of residue they might leave behind, or what they might dissolve in there. Stick with the commercial contact cleaners specifically made for the purpose. That's just my two cents worth.
As far as the probes go... No, none of these aftermarket probes that are "inexpensive" have the hardware for the scope to detect the attenuation setting. You may note on the actual Tek probe you have that there is a little pin next to the BNC connector. This is the "readout pin" that makes contact with a ring around the base of the BNC connector on the scope chassis, and this is what tells the scope what attenuation setting you have on the probe, according to the switch setting on the probe.
When using a probe that does not have the readout pin and its internal wiring, you just have to remember the atten setting and look at the right number on the V/div scale. That is, you use the knob value that is over the "10x" or "1x" indicator light, appropriately.
Most of the time you will be using 10x attenuation anyway. When you use a 100x probe then you need to multiply the 10x indication by 10 again.
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Ah ok, good to know. I didn't realize that the little pin is what tells the scope to switch the light from 1X to 10X. That is really all it's doing on this scope, correct?
I just did a little experiment with a few slider pots that I had from an old stereo, and noticed that even the high quality Deoxit doesn't actually "remove" really any of the gunk from it, and only removes a very small amount when it is "flushed" after a min or so. When I loosened the gunk up with Deoxit, and then put a little PB on it, the gunk immediately came off when I blotted it with a paper towel. Afterwards, it appears the IPA rinse removed all of the PB and Deoxit and left the slider nice and clean, and functioning way, way, way better than the "control" slider and also the Deoxit slider both with and without rinsing.
HAHAHA Factory warranty.... I WISH! If only, if only............
What then about your comment regarding the use of WD40 on badly oxidized/dirty switch contacts before? Both PB and WD have the same petroleum distillate as their main ingredient. However, I guess there is a bit of a difference between using it on an exposed and easily accessible part and an enclosed pot... I really do not want to be taking the back cover off of each of these pots to clean them out. who knows if I would ever get them back together if there's a spring in there that decides to shoot all the parts out in my face..
I guess if this D5 just isn't cutting it, I should try and locate some kind of better contact cleaner. The manual does specifically say not to use petroleum ether products to clean anything. I guess I'll just have to try Grainger for some aerospace contact cleaner, or order something. What would you suggest?
I still think it may be a good idea to rinse the pots out afterwards with IPA, what do you think?
Never mind, It seems the more I work the knob back and forth, the less "noise" I get. I'll just sit here and change the settings repeatedly for a while until it's no longer noticeable!
It's mainly the CH2 coupling switch under the V/DIV knob giving me trouble still, but it's also the position knob. All the other knobs/switches seem to be working fine now.
Also I just want to add that I definitely needed to adjust the tuning capacitor on the probe when I moved it from CH1 to CH2, so, like you stated, it is definitely necessary to adjust them when moving them from one channel to another, at least on my scope.
On another note, for the Arduino LCD I remember you saying that the Parallax one is the best because it only takes up a few spaces on the duino's output. Well, I think I've found out how to make that with a generic LCD and an I2C chip. Check this out and let me know if you think it's a good way to go.
http://electronics-diy.com/two-wire-i2c-arduino-lcd-display.php
Brian
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Yes, the readout pin just tells the scope to switch the indicator light. It doesn't do anything else in the scope.
No, that wasn't me who suggested the WD-40 before, I think it was Pirate. If it works, great. If it screws up your pots and switches... then what are you gonna do?
Just don't get any on those special attenuator boards, the SM specifically warns against that.
Yes, the Parallax LCD has some kind of serial interface wired in to give it the 1-data-line capability. There is an Arduino library of function calls for the Parallax LCD using its interface. I don't know if this will also work with your chip+generic LCD. You may have to write your own library functions for it! There are many libraries for the various LCD types, see the "playground" link below.
Ah... I see that the link you provided has already taken care of the necessary I2C libraries, that's great! The I2C uses 2 wires and the Parallax only one, but sure, it seems like a good project to try. Probably a lot cheaper than the Parallax LCD too. But no speaker.
http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary (http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary)
http://playground.arduino.cc/Code/LCD (http://playground.arduino.cc/Code/LCD) (scroll down for the Parallax 3-wire LCD library)
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I don't think it was me suggesting WD-40 for the pots on a scope. I used that trick suggested by AllAmerican5 Radio (Youtube) for treating the pot on my old Triplett meter but I don't think I would risk that on anything inside my scope. It does sound like something I might suggest though.
Bill
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[quote author=TinselKoala link=topic=15536.msg440014#msg440014 date=1424911163
Ah... I see that the link you provided has already taken care of the necessary I2C libraries, that's great! The I2C uses 2 wires and the Parallax only one, but sure, it seems like a good project to try. Probably a lot cheaper than the Parallax LCD too. But no speaker.
http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary (http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary)
http://playground.arduino.cc/Code/LCD (http://playground.arduino.cc/Code/LCD) (scroll down for the Parallax 3-wire LCD library)
[/quote]
I didn't know the 3-wire had a speaker as well. Oh well, the 4-wire generic will have to do for now. Once I know what else to get from Digikey or one of the others I'll grab up one or two of those chips. I'd get the Parallax, but I can think of quite a few other things that I'd rather put $40 towards, like a good power supply, a FG, Variac.....
I dug out my old vid cam earlier and found a mount for a tripod, so now all I need to do is find the cable to connect it to the PC and get or make a tripod, and I'll be able to stop nauseating people with my shaky vids
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Brian:
I hate to tell you this but in my opinion you made a mistake using the PB Blaster. That is noxious stuff for eating through rust to take nuts off of bolts and stuff like that. That stuff even smells like it means business. I know it from the brand "Screwloose." The WD40 is safely assumed to be essentially benign. Who knows, but potentially the PB Blaster could eat through the carbon or plastic resistive track inside a pot over several months. It's simply nasty stuff if it looks and smells like I think it does.
MileHigh
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Brian:
I hate to tell you this but in my opinion you made a mistake using the PB Blaster. That is noxious stuff for eating through rust to take nuts off of bolts and stuff like that. That stuff even smells like it means business. I know it from the brand "Screwloose." The WD40 is safely assumed to be essentially benign. Who knows, but potentially the PB Blaster could eat through the carbon or plastic resistive track inside a pot over several months. It's simply nasty stuff if it looks and smells like I think it does.
MileHigh
I haven't used it on anything but the one slider that I did the experiment with. That is exactly why I did it on something that doesn't matter, and brought it up in the forum before using anything like that on something that does matter, like the scope. :)
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There must be an issue with using my computer to put a signal to the scope....
For some reason, the 465 displays the exact same trace no matter what signal I output from my PC. This is the case whether I connect the probe to Left, Right, or Ground. The sounds change in the headphones I wired in, and on proper channels and all that.
If I hook up the 'ground' to the ground out of the PC, it cancels out the signal.
What I see when I hook it to the PC out is a crappy looking sine wave trace at 150V.
I tried various different settings - AC and DC coupling show the same trace.
Trigger level does nothing.
Anything but "A" on Horizontal Display makes it extremely bright except for the first half of the sine wave.
I didn't bother switching to one of my Tek probes to see if the sine wave trace looked any better. seems pointless to do.
I also disabled all audio enhancements and DC offset cancellation, etc. It should be 'direct output'.
About to make a quick video to show what I am talking about, then I'm going to figure out how to use the GR Oscillator and see what that looks like on the scope.
https://www.youtube.com/watch?v=E9l-EnME9Vw
Brian
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There must be an issue with using my computer to put a signal to the scope....
For some reason, the 465 displays the exact same trace no matter what signal I output from my PC. This is the case whether I connect the probe to Left, Right, or Ground. The sounds change in the headphones I wired in, and on proper channels and all that.
If I hook up the 'ground' to the ground out of the PC, it cancels out the signal.
What I see when I hook it to the PC out is a crappy looking sine wave trace at 150V.
I tried various different settings - AC and DC coupling show the same trace.
Trigger level does nothing.
Anything but "A" on Horizontal Display makes it extremely bright except for the first half of the sine wave.
I didn't bother switching to one of my Tek probes to see if the sine wave trace looked any better. seems pointless to do.
I also disabled all audio enhancements and DC offset cancellation, etc. It should be 'direct output'.
About to make a quick video to show what I am talking about, then I'm going to figure out how to use the GR Oscillator and see what that looks like on the scope.
Brian
I would like this to be figured out as well. I never thought of hooking up my scope to "see" the music I play on my computer all of the time.
I didn't know we could do that.
I also do not know how to do that.
If it is as easy as probing the 3.5mm output cord from my computer then, it will be easy. Somehow, I don't think it is as simple as that. I will keep watching here to find out how to do this.
Bill
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I would like this to be figured out as well. I never thought of hooking up my scope to "see" the music I play on my computer all of the time.
I didn't know we could do that.
I also do not know how to do that.
If it is as easy as probing the 3.5mm output cord from my computer then, it will be easy. Somehow, I don't think it is as simple as that. I will keep watching here to find out how to do this.
Bill
It appears that the PC headphone jack is outputting an AC signal in order to power the headphones that overpowers any waveforms from the audio that I would be able to see on the scope. Therefore it is necessary to run the PC output signal into some sort of "filter device" in order to kill the main power signal and only leave the audio waveform.
Now that I think about it... The output signal from the PC is an ACTIVE signal, in order to power the unpowered listening devices (headphones). The signal that is needed in order to watch the waveforms on the scope is a PASSIVE signal. So now, to look up how to transform an active signal to a passive signal.. Usually it's done the other way around via amplifier..
I'm no audio expert by any means, so I could be completely wrong about that. I could be doing something wrong, or it could be something entirely different. We'll just have to wait and see what solution is brought forth by people who know more about this.
Brian
**There must be something that I'm missing as far as the whole "150V" thing.... My probe was on X10.... but I don't see how my PC could POSSIBLY be pushing 150VAC out the headphone jack... maybe 15V but more likely 1.5V. My scope MUST have been being deceived, somehow. The loopback to the PC scope only showed 1.2V, but that's internal loopback via software, so I don't see how that would apply whatsoever to what comes out of the audio jack.
I've been searching "Active to Passive signal conversion" and coming up with junk for 3D video projection and nothing for audio, which tells me that I'm missing something very simple. All in all, a bit confused.... Maybe an Arduino based FG is going to be a better way to go...**
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Well it appears that this was a software issue of some kind.
I am currently running the "Wave Gen" feature from Visual Analyzer and I am able to detect the PROPER signals perfectly fine.
I will do some more PC FG/Scope testing tomorrow, and possibly make another vid of the performance of the PC FG's that I have and all that.
So, Bill, yes, we can in fact hook directly in to the 3.5mm's output with the scope and measure the traces. It is as easy as that! :)
Well, as long as you use the correct playback software and disable all of the "enhancement" features on the PC. If you would like, I will try and figure out what playback software works best for sending directly out to the scope for viewing. So far, Visual Analyzer seems to work pretty good as a FG, and has many other tools to immerse yourself in. Seems to be a good program to have in addition to the Soundcard Scope. That prog's FG doesn't seem to be of any use to me, but the Scope part's trace seems to be close to the trace on the Tek 465. However, it is still running on internal loopback, so I won't know exactly how good of a PC scope it is until I make a BNC to 3.5 connector at some point, which will be easy.
Brian
Brian
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There must be an issue with using my computer to put a signal to the scope....
For some reason, the 465 displays the exact same trace no matter what signal I output from my PC. This is the case whether I connect the probe to Left, Right, or Ground. The sounds change in the headphones I wired in, and on proper channels and all that.
If I hook up the 'ground' to the ground out of the PC, it cancels out the signal.
If you cannot connect the scope ground to the HP jack ground (sleeve connection) without killing the AUDIO signal to the HP jack, then you can go no further until you figure out why. Without the scope's signal ground connected to the laptop's signal ground, you will see all manner of AC noise when connecting a probe/scope input.
I have three different models of laptops here and I do not have any similar issues as what you describe. I can, using adapters, plug my laptop HP output directly into a stereo receiver's line inputs or into a scope's inputs without any problem.
Some HP/speaker amplifier IC's use circuity to detect when a HP is plugged in, and I believe I have seen one that floats the sleeve to a DC potential to eliminate cap coupling the HP output. Possibly connecting the scope ground may be messing with that HP detect circuitry. But again, I have never had a similar issue with my laptops.
If your laptop has a third prong on its AC cord, use your DVM set to low ohms and measure between the HP jack sleeve and the third prong (ground) on the laptop AC cord. Report back what you measure.
Also, check for continuity between the scope's ground and its AC cord third prong (I am assuming it is not cut off and that the laptop and scope were plugged into the same AC duplex/power strip).
Try running the laptop only on its internal battery (unplug the charger) and see iif you can connect the scope ground to the HP jack sleeve without muting the sound in the headphones. Also make certain the cord you made up is wired correctly.
What I see when I hook it to the PC out is a crappy looking sine wave trace at 150V.
If you cannot connect your scope ground to your HP jack ground, this "crappy sine wave" is what you will see.
I tried various different settings - AC and DC coupling show the same trace.
Trigger level does nothing.
Anything but "A" on Horizontal Display makes it extremely bright except for the first half of the sine wave.
I didn't bother switching to one of my Tek probes to see if the sine wave trace looked any better. seems pointless to do.
I also disabled all audio enhancements and DC offset cancellation, etc. It should be 'direct output'.
About to make a quick video to show what I am talking about, then I'm going to figure out how to use the GR Oscillator and see what that looks like on the scope.
https://www.youtube.com/watch?v=E9l-EnME9Vw
Brian
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Well it appears that this was a software issue of some kind.
I am currently running the "Wave Gen" feature from Visual Analyzer and I am able to detect the PROPER signals perfectly fine.
It seems to have something to do with sending the signal directly to output. I have to have the "send direct" box checked in the Wave Gen in order to get the proper trace on my scope.
I will do some more PC FG/Scope testing tomorrow, and possibly make another vid of the performance of the PC FG's that I have and all that.
So, Bill, yes, we can in fact hook directly in to the 3.5mm's output with the scope and measure the traces. It is as easy as that! :)
Well, as long as you use the correct playback software and disable all of the "enhancement" features on the PC. If you would like, I will try and figure out what playback software works best for sending directly out to the scope for viewing. So far, Visual Analyzer seems to work pretty good as a FG, and has many other tools to immerse yourself in. Seems to be a good program to have in addition to the Soundcard Scope. That prog's FG doesn't seem to be of any use to me, but the Scope part's trace actually matches my Tek 465 nearly exactly, so it must be fairly decent.
Brian
Brian
Brian,
Have you tried just playing some music on the laptop while looking at it with the scope?
Keep in mind that the AC levels at the HP jack will be fairly low level with the HP's connected.
PW
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Yes, that signal is not coming from the PC's audio output, it's more like a distorted 60 hz hum. I can't see the horizontal scale so I can't tell the frequency of the display on the scope.
But it seems that you now have the issue sorted, by using different software and making some different output settings on the PC.
Selecting other Horiz Display modes than "A" "lock knobs" gets into the delayed timebase features of the scope and we aren't ready to go there yet.
For fun audio display of music try the X-Y setting on the Time/div knob with CH1 connected to the L and CH2 connected to the R speaker outputs. This will give you a complex "Lissajous" pattern instead of a horizontal sweep.
Jerobeam Fenderson:
http://www.youtube.com/watch?v=l8m5L2gqHPw
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Brian,
Have you tried just playing some music on the laptop while looking at it with the scope?
Keep in mind that the AC levels at the HP jack will be fairly low level with the HP's connected.
PW
PW,
I've edited my last post a little since you last read it.
I don't know what exactly the issue was, but for some reason it seemed to be a software issue with that Soundcard Scope program, since VA's FG is running fine, and I have the reference clip (ground clip) hooked to the 'ground' sleeve of the 3.5mm (well, the wire I ran off of a jack).
I wanted to test it with some simple FG waveforms first. That way I know what I am supposed to see, and know if the scope shows the correct trace or not.
Now that I have it working, and am seeing the correct traces, I will run some music into it while listening tomorrow, and play around some more with the PC FG's I have. Maybe I'll even figure out what was causing the issues with using Soundcard Scope.
I did notice that the trace drops about 2/3 amplitude when I plug the HPs in. With the output volume at 15% I'm reading about 225mV w/o HPs, and about 80mV with HPs.
Brian
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PW,
I've edited my last post a little since you last read it.
I don't know what exactly the issue was, but for some reason it seemed to be a software issue with that Soundcard Scope program, since VA's FG is running fine, and I have the reference clip (ground clip) hooked to the 'ground' sleeve of the 3.5mm (well, the wire I ran off of a jack).
I wanted to test it with some simple FG waveforms first. That way I know what I am supposed to see, and know if the scope shows the correct trace or not.
Now that I have it working, and am seeing the correct traces, I will run some music into it while listening tomorrow, and play around some more with the PC FG's I have. Maybe I'll even figure out what was causing the issues with using Soundcard Scope.
I did notice that the trace drops about 2/3 amplitude when I plug the HPs in. With the output volume at 15% I'm reading about 225mV w/o HPs, and about 80mV with HPs.
Brian
Brian,
Glad your getting it sorted out. The levels you are measuring sound about right, including the noted level drop when the HP's are connected.
Connect the L&R output to the scope channels 1&2.
Grab a tune off of youtube and play some music...
Don't forget to play with the X-Y mode as TK suggested at some point as well.
PW
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Greetings everyone,
I'm back at it with this scope today finally, and I'm running into some new issues.
I'm going to make a video to show as much as I can here in a few minutes, but I am first going to give a brief description of the issues.
It seems to have to do with the triggering for the most part.
After having it powered on for around 15 or 20 minutes, the trace started to get fairly unstable. It would 'jitter' around a lot, and had a horizontal line which seemed to 'start' from the right side and 'pull' the trace at the peripheral of the line. (I had two channels in, one top one bottom, line occurring on both traces).
At first, in order to get a stable trace on a different time/div setting from .5ms, I had to change from ALT to CHOP and put the trigger coupling to HF REJECT on both channels. It did this in both AUTO and NORMAL trigger modes.
-Among other issues that it is having which I will do my best to show in the video I'm about to make.
Brian
I don't know what kind of issues I may be having with my PC output again, but I went back to step 1 and hooked both channels to the calibrator loop on the scope and everything seems to be OK.
However:
In order to get a stable trace outside of the .5ms setting, I had to switch 'A trig coupling' to "HF Reject".. my settings are as follows:
[Input side] X10 probes; 20m/div; DC input coupling; CHOP
[Trigger side] Mode: AUTO; Source: NORM; Levels=0; Slope +; holdoff: Normal; Horiz: A.
If you are going to see what all this is looking like on your scope, put it on AC or DC trigger coupling (doesn't matter which on mine) and start at .5ms. Switch out of .5ms and see if you have to put it in HF Reject mode to get a stable trace.
On the ALT vertical setting, I have to have the trigger coupling on LF Reject for anything outside of .5ms, and DC trigger coupling on .5ms.
Ok, now there are some seriously weird things happening with this scope and the settings. Actual scope issues video time...
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https://www.youtube.com/watch?v=gEJV-UOGxqw&feature=youtu.be
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Brian:
It looks like there is nothing wrong with your scope. The beam is disappearing when you are not triggered. I suggest that you watch most of the clips from this link:
https://www.youtube.com/user/AllAmericanFiveRadio/search?query=oscilloscope (https://www.youtube.com/user/AllAmericanFiveRadio/search?query=oscilloscope)
You have to adjust the trigger level to get a stable waveform. It's the most important adjustment for getting a stable waveform.
There is nothing to clean in your scope. Over the next week or two you need to learn how to use your scope, then perhaps consider working on it. However, it looks like the scope is fine and there is nothing for you to do to it.
MileHigh
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When I was attempting to clean up the waveform/stabilize it and would change the trigger Level adjustment, nothing at all would happen.
I will try again, though. Just to be positive.
I will watch the vids on that page that have to do with the O-scope, plus some others look pretty interesting also.
This is obviously after I learn how to use my equipment, but I was thinking a great place to start experimenting might be with tank circuits and crystal radios, and that channel fits right in there.
Brian
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Yes, Brian, when the trigger mode is not in "AUTO" the scope's display blanks and shows nothing when the waveform is below the trigger level. This is done to save the phosphor. Like if you aren't actually using the scope but you have it on to keep it warm, there is no point in having a straight line burning the phosphor, so the scope blanks the display in the Normal trigger modes. This is not a problem. I usually use "Auto" to set baselines and to look at very small signals, then switch to Normal so that the display blanks when not actually viewing a signal or the signal is below the set Trigger Level.
You adjust the trigger Holdoff a lot during the video and I kept wanting you to adjust the Trigger Level instead. Also you need to make sure the trigger Source is on the channel you want to trigger on! If you are triggering on CH1 and you turn that channel off by selecting Ground on the input coupling switch, the scope can't trigger! I can't see the scope's controls clearly enough in the video to see what's going on but it seems to me that the thing is behaving fairly normally as far as I can see.
It may be that there is some extra noise coming in that is causing it to be unstable unless HF or LF filtering is on. You are changing so many things and I can't see the critical settings well enough to diagnose this problem. It may be that the Holdoff control doesn't need to be perfectly on the "normal" line to get a stable trigger; this may be a calibration issue or a result of the noise on the signal.
Instead of using "Chop" please use "Alt" on the Vert Mode, connect both probes to the Calibrator, then select either CH1 or CH2 on the Trigger Source instead of "Norm". Then use the Trigger Level control to try to get a stable display. Check the difference between Auto and Norm trigger Modes as you vary the V/div setting on the channel you are triggering on. In Norm Mode the screen will go blank when the trigger level is set out of the range of the signal amplitude. This will also depend somewhat on the vertical position of the trace, you can take the trace out of the trigger level by moving it up or down on the screen and if you are in Norm Mode the screen will blank when you do that. This is what you were seeing in part of the video where the traces would disappear as you moved them up or down with the Vert Position control.
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Yes, the AllAmericanFive radio guy is fantastic and knows what he is talking about. I find his videos fascinating and very educational. He actually did a video and mentioned my Tripplett meter as he has one as well. He came up with the battery hack that I use because they no longer make those old 30 volt batteries. Great guy.
Geeze, after watching that guy, and Dave at EEvlog, and listening to TK, MH and Mark...you would think that I would have learned a lot more than I have by now. Some of the info sinks in, and some of it goes right through and I have to learn it again..ha ha.
But seriously, check out that guy's videos Brian...they are indeed great.
Bill
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Yes, the AllAmericanFive radio guy is fantastic and knows what he is talking about. I find his videos fascinating and very educational. He actually did a video and mentioned my Tripplett meter as he has one as well. He came up with the battery hack that I use because they no longer make those old 30 volt batteries. Great guy.
Geeze, after watching that guy, and Dave at EEvlog, and listening to TK, MH and Mark...you would think that I would have learned a lot more than I have by now. Some of the info sinks in, and some of it goes right through and I have to learn it again..ha ha.
But seriously, check out that guy's videos Brian...they are indeed great.
Bill
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Ah, now I feel stupid.
I should have thought a little bit more about what exactly the different settings do and what they change.
Also, for some reason I was thinking that when part of the trace was going off-screen it wasn't affecting anything, that it was just simply going out of the viewing range. Now I know that's not the case.
As for the trigger level adjustment, I must have been thinking that it was as sensitive as most of the other controls. So far, now that I know WHEN to use it, it is the least sensitive control of all of them. Scratch that, it can be very touchy at times also. Starting to get the hang of things now..
I will be watching a lot more instructional videos in the coming days so I can not only avoid feeling stupid, but stop bugging everyone with stupid questions and false problems!! That AllAmericanFiveRadio channel is definitely a good place to start.
Brian
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Brian,
Here is a real quick and simple explanation of what the trigger and trigger level do.
Let's say you have the horizontal sweep set to 1ms per division. The trace effectively sits and waits off screen on the left side of the display until the scope receives a trigger pulse, which, like a starting pistol at a race, makes the trace race across the screen toward the right at the horizontal rate you selected (the 1ms per division). Once the trace gets over to the far right side of the screen, the trace is temporarily shut off (blanked) and at very high speed races back over to the left side and again just sits there and waits for a trigger pulse. And so on and so on... No trigger, no racing off to the right.
Now, let's say you have a sine wave input to channel 1 that goes from +1 volt to -1 volt. The trigger level is used to determine at what voltage a trigger pulse is generated. Note that your trigger level control is labeled as positive or negative, with zero being straight up. If you adjust the trigger level for +0.5 volts, when the incoming sine wave exceeds +0.5 volts, the scope generates a triggerpulse and sends the trace off and running across the screen. When the trace returns to the left side, it will again sit and wait, but only until the incoming sine wave again exceeds +0.5 volts, which produces another trigger pulse and again sets the trace off toward the right. This causes the trace to scan across the screen, overlaying a new image of the sine wave over the still fading out previous sine wave image. The images overlap perfectly because the trace is always starting out from the left side at the same point in the cycle of the sine wave (the point where the sine wave reaches the +0.5 volts that the trigger is set to).
Now, if you turn down the level of the sine wave being fed to the scope so that it only goes from +300mv to -300mv, and you don't readjust the trigger level, which is still set at +0.5 volts, the scope will never generate a trigger pulse because the incoming signal never exceeds the +0.5 volts that the trigger level is set to. This is why the trigger level control is important and needs to be adjusted for the most stable display of every waveform you display.
Stable repetitive waveforms such as those coming from a function generator or the calibrator are fairly easy to get a solid trigger from and produce stable displays that exactly overwrite the previous scan. Complex waveforms, such as music, are a bit more difficult to trigger on, but using the HF reject and attempting to set the trigger level so that the trigger is generated from the typically larger low frequencies (bass notes) will produce a usable display, particularly at lower sweep speeds.
Turn your trigger holdoff knob to "normal" (which is minimum holdoff) for now and just leave it there!! You won't be needing any holdoff for repetitive signals (FG, calibrator, etc)
PW
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Brian,
I thought I would add this regarding the trigger holdoff.
As in my previous post, when the trace reaches the far right side it returns to the left side very quickly and sits off screen waiting for the next trigger pulse. Once the trace gets back over to the left side, the trace has to rearm itself to prepare for the next trigger pulse. The trace normally rearms itself very quickly so it responds almost immediately to the first incoming trigger pulse that arrives after the trace returns to the left.
Adding trigger holdoff using the trigger holdoff control causes the trace to just sit there on the left side off screen ignoring any incoming trigger pulses for the amount of time the holdoff control is set for. Once the holdoff time expires, the trace again rearms and begins scanning to the right on the first trigger pulse received after the holdoff period.
This can be useful when looking at a series of brief pulses separated by a fair amount of time (such as data bursts).
For now, set the holdoff to normal and leave it there until you become more familiar with your scope. You will not be needing to use any trigger holdoff for a while.
PW
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Good stuff guys, it's all comin together nicely now. I'm finally starting to understand this nifty tool.
I noticed that the 'Scope' Visualization in VLC media player is pretty accurate. I'm able to get the settings right on the Tek to pretty much match the traces that it shows.
Too bad it doesn't have XY mode, though. Is there something that I am missing where I'm able to get a more focused X-Y trace? I notice that it's a little bit better when I unplug my headphones, so maybe it's just the quality of sound from the PC output?
It's not the quality of the music files... I downloaded the .flac files. Turned off all enhancements everywhere.
Seems I figured it out... X1 probe, Max volume from the PC, 50 or 100mv/div, high intensity, unplug headphones ( :( ) I'm sure there's a way to add a little power into the signal to compensate for the HP loss, but that's for some time later on. Unless it's uber easy..
Brian
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I'd still like to see what the X-Y trace looks like. With no inputs (both channel input coupling switches to Ground) the X-Y display should give a single non-moving dot, that you can position to exact center screen with the vert and horz position controls and focus to a tiny dot. Don't leave it there too long or too bright, it will burn the phosphor. Then if you give both channels the same input from the calibrator you should see a diagonal line. (Both channel V/div at same settings)
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TK -
Here's a video of me going through the X-Y display test that you suggested. I am able to get the centered dot with the inputs at Ground, but I do not get the single diagonal that it sounds like I should be getting. Let me know if you need any more info than what I gave about my settings. Hopefully it's just a human error issue, or at most a calibration issue.
In the video I had the probes on X1. I tried it before the vid with X10 and the only difference it made was where I had to have my V/div set, and gave the exact same traces.
https://www.youtube.com/watch?v=jnsx32d2krY
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Hmm. That looks "almost" normal, but there should be only a single diagonal line between the endpoint dots. Let's make sure you have the scope set properly.
The Time/Div switches should be locked together and on X-Y mode, the "Var" knob in the cal detent. Horizontal Display in "A" . For looking at the calibrator signal, the V/div controls should both be set to the same value and the "var" knob in its cal detent. No Bandwidth Limit. Yes, the Vert Mode should be in CH2 for the x-y display. CH2 "invert" out, not inverted. AC-coupled inputs should help center the X-Y display, that at least looks like it is working right. The x-y display is not triggered so the trigger controls shouldn't make any difference. Be careful about the Intensity control. If the display is working correctly you should be able to get decent brightness of the diagonal line without blasting out the endpoint dots.
Don't connect your probe Grounds to the Calibrator output! This short-circuits the Calibrator! The probe grounds are already connected to the Chassis ground internally by the BNC connectors and you should not have to connect them to anything when using the Calibrator... especially not the Calibrator output!
Please use 10x probe attenuation whenever possible, and set the V/div knobs appropriately!
The display "should" be a single diagonal line between the two endpoints. The scaling and angle of the line depends on the V/div settings of the channels. If both V/div knobs are set the same the line should be 45 degrees, sloping up from left to right, and the length scaled by the V/div settings.
If the display is different from that, like with the two lines, and the scope is set properly, there may be an issue with calibration, or the probes themselves even. Please repeat the test with the probes set to 10x and let's see if you can get a nice single diagonal line, bearing in mind what I said above. You may want to check and adjust the probe compensation adjustments again, using 10x attenuation, the normal time-domain display and the nice square wave from the calibrator according to the instructions for doing that.
(When the x-y display deviates from the single diagonal line this normally means that the two signals are out-of-phase. With both V/div knobs set the same, a perfect circle means 90 degrees out-of-phase and a diagonal line sloping _down_ from L to R indicates 180 degrees out-of-phase. See the image attached below. Since both signals are coming from the same Calibrator source they should be perfectly in phase. So there is some issue here, again presuming that the controls and probes are set properly.)
I noticed that it looks like both V/div readout lights are on in the upper V/div switch. This is a fault. When there is no probe with a readout pin connected, only the "1x" light should be on, and you need to remember to read the knob scale at the unlit 10x position when you are using 10x attenuation on your probe.
OH>>> never mind, I took another look and it seems that that is just a glare from the room light reflecting on the switch. Never mind.... :-[
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Note Brian's source is not an audio signal, it's the calibrator square wave. So two diagonal dots on the screen with very faint lines in between is correct. It looks like in the beginning of the clip the two input gains are too high so you don't see the two dots. Towards the end of the clip he turns down the input gains and all is good. The scope looks fine.
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TK -
Here's a video of me going through the X-Y display test that you suggested. I am able to get the centered dot with the inputs at Ground, but I do not get the single diagonal that it sounds like I should be getting. Let me know if you need any more info than what I gave about my settings. Hopefully it's just a human error issue, or at most a calibration issue.
In the video I had the probes on X1. I tried it before the vid with X10 and the only difference it made was where I had to have my V/div set, and gave the exact same traces.
https://www.youtube.com/watch?v=jnsx32d2krY
It looks right to me.
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Note Brian's source is not an audio signal, it's the calibrator square wave. So two diagonal dots on the screen with very faint lines in between is correct. (snip)
Well, maybe. My Tek 2213a gives a better balance between the bright dots and the line, though, when using the Calibrator input. The line shows up better than in Brian's video when the dots are reasonably bright. Maybe this is a result of the camera not showing the lines well in Brian's video. I still think the two parallel lines are weird, though. There should only be one line, with length depending on V/div settings and angle at 45 degrees if both V/div knobs and probes are set the same.
Inverting the CH2 input should make the line slope in the other direction, sloping down from L to R. With two square wave inputs of adjustable phase it is possible to have a square of 4 dots with very dim or invisible lines between them, or an "L" shaped line with two bright end dots and one dimmer corner dot, depending on the phase of the square wave signals. But two parallel diagonal lines.... I don't think that should be happening.
I've shot a little video showing the use of the x-y mode to display phase shifts, but I used a pair of sine wave signals instead of square waves. This does make a difference in the brightness of the displayed diagonal trace. I'll post the link to the video when it's done uploading.
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TK -
I had everything set the way you described it, except of course for the probe atten setting. I will try again with 10X, even though I tried that before I made the vid and got the same results, just had the shift in the V/div settings to compensate.
I will also try the same thing using the FG from my PC and a pair of in phase sine waves. If I don't get the proper diagonal line, I will adjust phase until I do, and post the results.
I will also try everything with the original Tek probes. First test with the cheaps then the Tek's, then second test with cheaps then Teks.
From what everyone is saying, it seems like the results of doing so from the scope calibrator varies in some brands/models.
The video I shot is showing the correct brightness that corresponds with what I see on the scope screen. I don't have it set to compensate for lighting conditions so that you see exactly what I see. I've been trying to adjust my lighting in here to give the best view without glare on the video, but I haven't managed to hit it right just yet. I'm working on setting up a mini-lab with some shelves and a big desk so I can give my equipment a more permanent home, and then hopefully I will be able to set up a more permanent lighting system for better vids. Maybe if I try LED lighting, or christmas lights..... haha
Brian
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On my TDS2024:
A 1kHz square wave using equal length cables to the channel inputs generates two dots. If I turn on infinite persistence then eventually two more or less diagonal lines form.
A 10MHz square wave also using equal length cables makes kind of a hysteresis "S" shape.
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Hmmm.... The "two lines" figure from MarkE looks to me like a little bit of phase difference in the two signals. At least that is what two signals with a slight bit of phase difference _should_ look like. But I agree, in a perfect world two perfectly in-phase and perfectly symmetrical square waves should produce two dots with a dim line connecting them or no line at all. A pair of in-phase sine wave signals will produce a more definite diagonal line. I think that the two lines that build up in MarkE's infinite persistence figure may indicate a slight bit of phase jitter or noise, possibly in the scope itself since the signals are coming from the same source, or an imperfection in the square wave signal.
My video demonstration using sine wave signals is here:
http://www.youtube.com/watch?v=mV1IHnIHaC8
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It is a slight asymmetry in the frequency response of the amplifiers. The driving signal has a rise time that is faster than either amplifier can track. If I drive with a signal that doesn't have such fast rise times, then I get the expected diagonal line seen below.
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Heh.... here are a couple of soundfiles to look at using X-Y mode....
http://frozenhaxor.pl/pliki/youscope.wav
http://frozenhaxor.pl/pliki/oscillofun.flac
Found these on a video demo here:
https://www.youtube.com/watch?v=3U7I3if3TtM
They display quite well on my Tek 2213a!
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So everything is looking pretty good so far. I'm not getting the diagonal line off the calibrator, but when I set it up off the calibrator with both traces overlapping, about 3 cycles on screen, and then switch to XY, I get two dots at very close to 45 degrees in the proper direction. When I invert Channel 2, it inverts the diagonal properly. See the pictures below.
I ran the same test using the two original Tek probes I have (the 6062A I rebuilt, and the 6065A that the scope came with) and the 6065A is acting up a little. I'd like to be able to use it with the 6062A when I need a pair of high quality probes, so if it's something fixable I'd like to try and fix it. I made a vid of the calibrator sq wave to X-Y with those probes and showed what the issue is with the probe. If it's too much of a pain to remedy I'll just set it aside for some other time.
I'm about to run both pairs of probes using the sine wave to make sure I get the actual line, play with the phase settings, and then check out the links that TK posted and have a little fun with it.
I got a little carried away getting my mini-lab set up or I'd have already done all this testing. But hey, at least I'm about ready to populate it, run a 110V dedicated line to it (all that I have there for now is an old ungrounded outlet!!) and set up some lighting..
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00224x_zpsmipym7fq.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00222x_zpsfa467i5m.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00223x_zpsvwlcd5pg.jpg
Vid should be done uploading shortly:
https://www.youtube.com/watch?v=msbXPU_l_aw
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How are you able to upload a pic to the OU server as an attachment and it show up as a link instead of the picture? I guess my method works fine, but I'd still like to know. Is it just the type of file you are attaching? Is it that if it's not a jpg or gif file, it displays as a link?
I mean, I like not having to click on a link and all that to see a picture, but in these forums it's better to have links instead of the pic, especially if there are multiple. Saves from having to load page after page just to go a few posts back or forward.
Brian
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My computer makes for the WORST FG of all time! The only thing that actually looks the way it should from the PC is a sine wave...
Square wave looks like a cross between sawtooth and square wave... and none of the others look good at all. I need to get my Arduino working as an FG, or maybe the Dell desktop that I picked up from storage set up and loaded with Linux and an FG since I have decent sound cards for it. Maybe running the output thru my yamaha stereo amp would help? I know it's not the scope, and It'd be nice to have a semi-decent FG to use until I get a real one.
I'm going to upload a few pics as soon as I get this camera/sd card issue resolved and add them to this post. They are pics of the diagonal line, circle, etc, and one or two of my horrible looking other waveforms.
After watching the Youtube video YouScope & Oscillofun and seeing what the song is supposed to look like on the scope, I realized that what I am seeing is definitely not correct. I made a vid showing what I see for most of the song. I hope it's just an issue with my PC soundcard but I somehow doubt that's the case. Whatever it is is likely the cause of my distorted waveforms (other than the sine wave).
https://www.youtube.com/watch?v=sPkQEFfGOfM
Here are some test waveforms (standard and XY) off my scope and PCFG.
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSawtooth-PCFG_zpsydiaz5rz.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSQ-PCFG_zpspmukkzwp.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSine-PCFG_zpsv7xrk0tq.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSineXY-PCFG_zps4ekkrzib.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSineXY-45OOF-PCFG_zpsuwkgcmjo.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSineXY-90OOF-PCFG_zpskllfhqko.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/1khzSquareXY-90OOF-PCFG_zpsvrcpsucv.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/10khzSquareXY-90OOF-PCFG_zpsch524ueb.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/20khzSquareXY-90OOF-PCFG_zpsq19blots.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/20khzSineXY-90OOF-PCFG_zpsp6kpnhsm.jpg
http://i1081.photobucket.com/albums/j347/Brian_Bloom/10khzSineXY-PCFG_zpsxqajwnrf.jpg
Time to crash. Goodnight everyone.
Just realized, it has to be a PC sound card problem, right? I mean, I get a good, clean square wave off the calibrator.... Right?? Or am I totally missing something, again?
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Well, the Sine waves look really clean and the 90 degree oop circle is perfect. Yes, I think your sound card is probably introducing distortion for the ramp and square wave signals and the "oscillofun" FLAC file. I'm puzzled as to why you need to turn it up all the way, though. I ran "oscillofun" just at normal volume in my speakers and at the same time took the headphone output directly from the front panel headphone jack into the 10x attenuated probes and was able to see the shapes fairly cleanly, with much less distortion than your video shows.
So like I said I'm puzzled. You should be able to just use the V/div scales to set the scope at more sensitive amplification and run the sound card at normal volume, and I don't see why you can't run the speaker output and the headphone output at the same time. I'm running a seven year old Asus motherboard with onboard sound, no separate soundcard. The probes shouldn't be loading the soundcard much at all, certainly not as much as headphones would. If you run the sound card at 70 percent volume you should get much less distortion from it, and if the scope's V/div settings won't display it at that output level I'd say that there is something wrong somewhere.
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PNGs always seem to display, TIFs don't seem to display. My scope puts out TIFs.
Your scope seems to be working OK. The fuzzy signals look like a high impedance in the probe ground. The awful square waves look possibly like an open ground connection.
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Yep. I thought also perhaps some distortion from running the sound card all the way up. This may have been necessary due to a high impedance in the ground connection also.
I just made a video playing the two sound files into the 2213a. Direct from the headphone output, volume at about 75 percent, speakers going too (with separate VC on the speakers). 10x probe attenuation, V/div settings 500 mV/div mostly, increasing to 200 mV/div at another segment (I misspoke in the video, was reading the "1x" position on the knob by mistake, but I inserted correction titles in the vid, the 500 and 200 mV numbers are correct.)
It will take half an hour or so to process and upload the video. It is much cleaner than what Brian showed, so I think that better connections and perhaps different settings will also work to clean up his display of the files as well. (I downloaded the files and played them directly using the Ubuntu native "movie player" app rather than playing them from the YT video player on the video I linked earlier.)
One weirdness for me is that the text in the "youscope.wav" file is displaying in mirror-image or backwards or something. Nothing I've tried has corrected that. Swapping channels makes the text run vertically instead of horizontally and inverting one channel makes it upside down, but still it appears backwards instead of straight.
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My video of the Youscope and Oscillofun audio files on the Tek 2213a is ready at:
http://www.youtube.com/watch?v=FoSPK1qRhSY (http://youtu.be/FoSPK1qRhSY)
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That's cute.
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Well, the Sine waves look really clean and the 90 degree oop circle is perfect. Yes, I think your sound card is probably introducing distortion for the ramp and square wave signals and the "oscillofun" FLAC file. I'm puzzled as to why you need to turn it up all the way, though. I ran "oscillofun" just at normal volume in my speakers and at the same time took the headphone output directly from the front panel headphone jack into the 10x attenuated probes and was able to see the shapes fairly cleanly, with much less distortion than your video shows.
So like I said I'm puzzled. You should be able to just use the V/div scales to set the scope at more sensitive amplification and run the sound card at normal volume, and I don't see why you can't run the speaker output and the headphone output at the same time. I'm running a seven year old Asus motherboard with onboard sound, no separate soundcard. The probes shouldn't be loading the soundcard much at all, certainly not as much as headphones would. If you run the sound card at 70 percent volume you should get much less distortion from it, and if the scope's V/div settings won't display it at that output level I'd say that there is something wrong somewhere.
I don't have to have it turned up all the way, but it helps a very little bit with the sharpness when I get above a certain volume. I can run it down to about 2% volume and still pick up the traces, especially with the sine wave (obviously with different v/div setting). It would help with the w/ or w/o HP's issue if I could eliminate that altogether and run the speakers and scope off the same audio source in sync, but the best I've managed to find for those settings is to enable both to be able to play separate signals at the same time. (I can't get my audio player to select both the HP jack and speakers simultaneously - but can enable both so I can play two different things at the same time.) If I were running Linux, I could probably add a setting to use both if I couldn't already.
I'm going to try eliminating all of my splitter jacks and the 6' headphone cable I'm using and chop the cord off an old pair of HPs to about 6" long and see if it's my cables/connections that are the problem. If that isn't it, when I get my desktop up and running, first thing I'll do is install an FG and try that. Maybe this Samsung laptop has some built-in filter device hardware that is causing the distortion. Whatever it is, it doesn't distort the Sine wave.
But as I mentioned before, since I do get a proper 300mv 1khz signal out of my calibrator loop on both channels, this CAN'T be a scope issue, it has to be an issue with something before the probe tips, correct? One thing I did notice when I was playing around swapping probes is that if the grabber tip isn't fully seated on the probe tip, it tends to distort the trace. Example: when I switched back to the pp-200 probes and hooked to the cal loop, my CH2 had a flattened square wave trace. When I gave the grabber a good squeeze onto the probe, it went back to normal as soon as I got it fully seated.
Also, I had previously checked my outlet to make SURE that it is wired correctly and has ground connected, and it's all good. However, it is the old style Anaconda 12-2 with the 12awg hot and neutral, and 14awg (or smaller) ground wire. That is likely the reason why, if I plug a small space heater into the same source (any outlet off the same breaker) it distorts my trace. In XY, it will take the two dots and "pull" them to the left. That is why I intend to run at least one dedicated 20A circuit up to my workstation. If it comes down to it, I'll add a second so my scope and other similar equipment can have a dedicated line, and soldering iron, etc can hook into another. This probably has something to do with the way my house is wired. I only have a 100A box, and my ground is tied into my neutral. If I must, I'll rewire it so that I can separate the two, but that shouldn't be necessary, hopefully.
Just checked-Space heater is only two-prong, so that's not it. maybe it has to do with running a resistive load that big off the same circuit? Just thought I'd let you know about that in case it has anything to do with any of this somehow.
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PNGs always seem to display, TIFs don't seem to display. My scope puts out TIFs.
Your scope seems to be working OK. The fuzzy signals look like a high impedance in the probe ground. The awful square waves look possibly like an open ground connection.
Maybe the receptacle tester I used wasn't working properly, but it said that the outlets are wired correctly and grounded. Could be the extra small ground wire of the old Anaconda 12-2. I have a new 12-2 romex lead ready to rock and roll, and will stick it up thru the hole that I drilled for it here shortly and test it that wayn.
Another thing here is that my laptop charger is only a two-prong, so it has no designated ground lead to hook to, only the neutral.
If it's not that, or my HP wire config, and the new circuit doesn't fix it, maybe it's that the ground and neutral busses in the panelbox are bridged instead of separate? I could fix that, I'd just have to shut down the power to the house for an hour or so. A quick fix to that might be just running a piece of romex to a ground rod outside and connecting my outlet/box grounding to that. Lets hope it doesn't go that far, though. Or maybe it is the PC's integrated sound card, but I wouldn't think so since it's a fairly high end computer even being that it's a couple years old.
[just noticed someone's watching my $240 pool cue listing on ebay, hopefully they buy and that Interstate FG is still available in 5 days!!! :)))))) ]
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In terms of keeping your equipment from doing bad things, having all the green wires connected together is important practice. When using something with an isolated supply lie a laptop, that connection will come through the signal common, in this case the ground connection of the stereo headphone ouput.
What I was referring to was the connection between the audio common connection (internal circuit common or ground of your computer) and the oscilloscope. This would be a problem between the audio jack and the oscilloscope Ch 1, & Ch 2 inputs. An easy way to check is to set your oscilloscope trigger to the AC line and sweep to 5ms / div and see if the signal envelope is locked to the line. If it is, then the signal return is being supplied through the AC mains green wire at the scope and leakage capacitance through the laptop charger.
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In terms of keeping your equipment from doing bad things, having all the green wires connected together is important practice. When using something with an isolated supply lie a laptop, that connection will come through the signal common, in this case the ground connection of the stereo headphone ouput.
What I was referring to was the connection between the audio common connection (internal circuit common or ground of your computer) and the oscilloscope. This would be a problem between the audio jack and the oscilloscope Ch 1, & Ch 2 inputs. An easy way to check is to set your oscilloscope trigger to the AC line and sweep to 5ms / div and see if the signal envelope is locked to the line. If it is, then the signal return is being supplied through the AC mains green wire at the scope and leakage capacitance through the laptop charger.
Made a vid to show the results of this test. From what I gather from your explanation, for some reason I do not have a ground/common connection from the laptop to scope. Let me know your thoughts on the matter. Also, I pointed out that there is a little dot to the left, just off screen when centered, when the scope is in standby mode. Is that normal? Watch vid and then you will understand the pic that I linked to.
https://www.youtube.com/watch?v=jkDdHDRAoyQ
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00254_zpsxtm5ctp2.jpg
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Yes, that little dot (or dots) off to the left, out of view offscreen when screen is properly centered but blanked from a no-trigger condition, is normal. At least both my 2213a and the HP180a do it too.
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Ah, I think i may have figured out the problem... possibly. but it's not so easy for me to verify this....
I have tripped over my power cord/HDMI cord on multiple occasions and damaged the charger port of my computer... and it is now to the point where it rarely actually charges the battery when plugged in. The computer will run off the AC source, but I have to squeeze around the port and play with it a bit to get it to charge, and it's become really hard to get it to actually charge. Upon closer inspection, I see that there are in fact two contact points to the outer ring (neutral/ground connector) of the plug, and one, being most likely the ground from the laptop, must have a broken connection from the motherboard. If I am correct and that is the case, then I have found my reason why I am not getting a solid ground connection between the laptop PSU and the scope.
At some point I will have to take my laptop apart to access the PCB where the port is attached and fix it. I just ordered an original replacement off ebay for $4, so when I get it and replace it I will try again with my laptop and see if that was the issue. I'm not going to bother trying to fix the one that's in it, so I only have to take it apart once.... going to have to grind down a soldering iron tip to a superfine point for this task. I broke a 30W soldering iron the other day (heater wire broke free from contact) and am going to mod it and make it a 15 or 20W. which would you suggest I go with? my 6-8W is battery op and kinda sucks, and next one up from that is 25W. Also, should I spread out the heater wire, keep it all at the back, or all at the front? _sorry for the off-topic question_!!)
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Made a vid to show the results of this test. From what I gather from your explanation, for some reason I do not have a ground/common connection from the laptop to scope. Let me know your thoughts on the matter. Also, I pointed out that there is a little dot to the left, just off screen when centered, when the scope is in standby mode. Is that normal? Watch vid and then you will understand the pic that I linked to.
https://www.youtube.com/watch?v=jkDdHDRAoyQ
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00254_zpsxtm5ctp2.jpg
It looks like the common is open between the headphone out and the oscilloscope input.
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It looks like the common is open between the headphone out and the oscilloscope input.
If what you're saying means that the whole laptop to AC source ground connection being broken doesn't matter, and what matters is the soundcard ground to scope ground, I'm not sure what the problem is. I checked continuity in the probe's grounds, and they're good, and checked continuity in my headphone cable setup, and they're all good. So what you are telling me is that either the PCB ground to HP jack ground is broken/not connected, or my scope input connector to machine internal ground is broken?
I checked the continuity between the collars of the BNC and the ground input plug on the face of the scope, and it's good. It's also good from the scope plug ground prong to the BNC collars and the ground connection plug on the face of the scope. So it's back to the PC, correct?
I'm so sick of having problems with stuff!!!! I just want it all to WORK so I can LEARN HOW TO USE IT ALL!!! AHHHHHH
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If what you're saying means that the whole laptop to AC source ground connection being broken doesn't matter, and what matters is the soundcard ground to scope ground, I'm not sure what the problem is. I checked continuity in the probe's grounds, and they're good, and checked continuity in my headphone cable setup, and they're all good. So what you are telling me is that either the PCB ground to HP jack ground is broken/not connected, or my scope input connector to machine internal ground is broken?
I checked the continuity between the collars of the BNC and the ground input plug on the face of the scope, and it's good. It's also good from the scope plug ground prong to the BNC collars and the ground connection plug on the face of the scope. So it's back to the PC, correct?
I'm so sick of having problems with stuff!!!! I just want it all to WORK so I can LEARN HOW TO USE IT ALL!!! AHHHHHH
There is a simple test: Hook your laptop to an AC powered stereo. If you get a bunch of 60 cycle hum then you have a bad ground connection. If not, then there is something else going on with your oscilloscope set-up.
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There is a simple test: Hook your laptop to an AC powered stereo. If you get a bunch of 60 cycle hum then you have a bad ground connection. If not, then there is something else going on with your oscilloscope set-up.
When I have the laptop hooked up to the AC powered stereo unit (with the unit on only stereo mode, no enhancements such as surround, dolby, etc) It works perfectly. no hum at all. It plays music without any hum at any volume, without any input from the laptop with the stereo volume up, and with a 1khz sine wave output.
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It works perfectly when plugged into an AC powered stereo. no hum at all.
Brian,
When you say "it" works perfectly, do you mean that when the laptop HP jack is connected to the input of a stereo audio amplifier, you can produce, for example, a 1KHz sine wave output from your FG software and HEAR a nice steady 1K tone from both the left and right channel of your stereo's speakers (or headphones)?
PW
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Brian,
When you say "it" works perfectly, do you mean that when the laptop HP jack is connected to a stereo audio amplifier, you can produce, for example, a 1KHz sine wave output from your FG software and HEAR a nice steady 1K tone from both the left and right channel of your stereo's speakers (or headphones)?
PW
1khz sine wave played from PC FG into AC sound system set on stereo-
https://www.youtube.com/watch?v=zfmSXja5Iz0
I also noticed that when I have it on X-Y with no input and on 5mv/div, it's not just a dot in the center. If I turn the intensity up a little, I can see what looks like half of the infinite symbol emerging from the dot towards the top of the screen, so more or less a teardrop shape with the point being at the dot.
(where's the 'smashing my head into the wall' emoticon thing?? :( )
Brian
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1khz sine wave played from PC FG into AC sound system set on stereo-
https://www.youtube.com/watch?v=zfmSXja5Iz0
Brian
Brian,
OK, the FG software appears to be working fine.
From your previous video:
Regarding your "dot" on the far left. It's probably just the "beam off" blanking level for your trace while waiting for a trigger. What does it matter if you have to crank the H position way over and crank up the brightness to see it?
I don't see evidence of what I would consider an open ground in the video you posted.
Personally, I think you should for now just focus on getting decent displays using just one channel. Use only channel one for a while, set the H position so that the trace is centered left right and leave that knob alone for now. Same with the trigger holdoff. Set it to norm and leave it there.
Select to display only channel one with trigger source set to channel one. Once you get good at displaying various waveforms with channel one, then you can move on to dual channel use. Before doing so, practice getting decent channel one displays so that they are centered in the upper half of the display (using vertical position) with the vertical sensitivity set so that the displayed waveforms do not use any more than the upper half of the display. This clears the lower half of your display for use with channel two.
I am not sure what your calibrator's frequency is, they are typically 1KHz, but I believe its amplitude is 300mv pk to pk. Using just one probe and channel one, get good at displaying the calibrator signal. I would select AC coupling on the channel input and AC coupling on the trigger source (just in case any source has DC offset).
Once you are confident with using channel one to produce stable views of 3 or 4 cycles of the calibrator waveform, set your PC based FG so that it produces a square wave of the same frequency (1K?) and of similar amplitude as your calibrator. Connect your scope probe's ground lead to the HP jack's sleeve (gnd) connection. You should then be able to move your probe tip connection between the calibrator and one channel of the laptop's HP output, and without flipping any scope switches, see the same waveform displayed in a stable fashion. Adjust the PC based frequency and amplitude as necessary so that when it is displayed, it closely matches the calibrator display. The point of this is, that if you can get a stable display of the calibrator signal, and if the calibrator and PC based FG are producing the same signal, you should be able to see either one without changing any scope settings.
Now, once you can do that without issues, and if you have the calibrator or FG display confined to the upper half of the scope's display, select ALT for a two channel display. Set the CH2 vertical sensitivity the same as CH1's sensitivity (and with AC input coupling). Connect a probe similar to CH1's probe (X1 or X10) to the CH2 input and connect its tip to the same point you have the CH1 probe tip connected. Adjust the CH2 vertical position control so that the CH2 waveform is centered in the lower half of the display. You should now have two identical looking waveforms displayed, CH1 in the upper half, CH2 in the lower half, and the displayed waveforms should not be overlapping vertically. You should also be able to move the probe tips between the calibrator and the PC based FG output with the displays remaining stable and looking similarly.
Once you get this far, you can connect CH2's probe to the second channel of the PC based FG output for display of independent FG channels.
Regarding your last video:
Does your stereo audio amp have a preamp out or record output?
You might consider using a pair of phono cords to bring the line/record out from the stereo over to the scope and connect your scope to the phono plugs at the end of the phono cords. In the absence of phono to BNC adapters, you can use alligator clip leads to go from the tip of the phono plugs to the scope probe spring hooks. Trying to hook the phono plug tips directly might be a bit rough on your probe hooks (alternately, cut and strip the ends of a spare phono cord). You only need to hook up one probe ground lead to one phono plug's ground (or use another clip lead between your scope's ground jack and one of the phono plug shells.
But, as above, consider using only one channel for a while until you are good at getting a stable display on just channel one.
PW
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Made a vid to show the results of this test. From what I gather from your explanation, for some reason I do not have a ground/common connection from the laptop to scope. Let me know your thoughts on the matter. Also, I pointed out that there is a little dot to the left, just off screen when centered, when the scope is in standby mode. Is that normal? Watch vid and then you will understand the pic that I linked to.
https://www.youtube.com/watch?v=jkDdHDRAoyQ (https://www.youtube.com/watch?v=jkDdHDRAoyQ)
http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00254_zpsxtm5ctp2.jpg (http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00254_zpsxtm5ctp2.jpg)
The dot is normal and usually off the screen to the left when you are displaying a signal.
To check for the improper ground 60Hz hum, you should change the Trigger Source to "LINE" and see if the trace stabilizes. I kept wanting you to do this in the video but you didn't. :'( You used every other control but the one that would show the 60 Hz noise if it was there. Also at 6:25 or so when the screen blanks... you are in NORM trigger mode and the trigger _level_ is set outside the range of the signal, so the screen blanks! Slow down please... think about what you are doing. If the screen blanks but you know you have a valid signal input, the FIRST thing to check is the Trigger Level setting. Ah...I'm writing this as I'm watching and at 6:35 or so you finally adjust the Trigger Level and get a trace. Good! But you never tried "LINE" on the Trigger Source.... If there is a 60 Hz hum coming from the lack of proper grounding this will show up as an "envelope" for your actual main signal, making it wobble up and down or other weirdnesses. If you select "LINE" on Trigger Source the scope will trigger on the mains input to the power supply and any weirdness caused by the 60Hz hum will stabilize. The main signal will "run free" of course but with the proper timebase setting for 60 Hz you can view the stable "envelope" or other 60Hz weirdness on the main signal when "LINE" is selected as the trigger source.
A 60 Hz waveform has a period of (1 sec/60Hz) = 0.0166 seconds or 16.7 milliseconds. 3 full cycles would then take 50 milliseconds. Your screen is 10 divisions wide, so to display 50 milliseconds worth of signal across the screen you set your timebase to 5 ms/div. Then set Trigger Source to LINE. If you then see a stable "envelope" of three cycles with your main waveform running inside that envelope, you have identified your problem to be a 60 Hz hum most likely coming from a bad signal ground.
You could also do this: With the connections between scope and headphone jack on the PC made as you have tried them, and both the Scope and the PC turned OFF and unplugged from the wall, use a DMM to check the ground connection for continuity and resistance. Touch one DMM probe to the BNC shields at the scope and the other DMM probe to some ground on the PC, like the USB shield or the headphone jack outer part, to see if there is high resistance or open circuit in your ground connection from the scope to the PC.
Don't get so frustrated! You are learning a whole lot about scope operation and etc. that you would never have learned otherwise, and you have the satisfaction of bringing this classic and sensitive instrument back to life! That is nothing to sneeze at. The Oscilloscope is the King of test equipment and is a complex bit of apparatus, as you can see, and your scope isn't exactly a "beginner's" scope, it is considerably more complex than many lesser instruments, with its delayed timebase features etc. You are on a very steep learning curve and you are doing just fine, so don't be so hard on yourself.
ETA: Take PW's advice to heart. I can add this: SLOW DOWN. Every time you change a setting, stop for a few seconds, observe, and _think_ about what you see or don't see. The scope is a very complex instrument, but it is dumb, and it only does what you tell it to do. If you tell it nonsense, you will get nonsense back from it. GIGO applies in full force here.
And lighten up, you are getting such a valuable education here, and I'm quite sure that others are watching along and also benefitting from our explorations here.
And here's your head-banging smiley:
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When I have the laptop hooked up to the AC powered stereo unit (with the unit on only stereo mode, no enhancements such as surround, dolby, etc) It works perfectly. no hum at all. It plays music without any hum at any volume, without any input from the laptop with the stereo volume up, and with a 1khz sine wave output.
Well when a circuit cannot support DC (the exponential decay in your square waves) and the common is connected, then somewhere a blocking capacitor has been inserted, such as by setting the oscilloscope input to AC.
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Well when a circuit cannot support DC (the exponential decay in your square waves) and the common is connected, then somewhere a blocking capacitor has been inserted, such as by setting the oscilloscope input to AC.
MarkE,
I think we should all just focus on getting Brian to the point where he can get stable, correctly triggered displays on his scope.
A bit of tilt is the least of his problems at this point.
In the last video of his scope in action, I wanted to turn off CH2, speed up the horizontal and adjust trigger level for a stable display. Looks like he had one of the channels vert. sensitivity cranked up much higher than the other (or different probe factor), horizontal sweep way to slow, and that it was not triggering. It has been some time since Brian has produced a video of a stable display, tilt or no tilt.
PW
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(snip)
I also noticed that when I have it on X-Y with no input and on 5mv/div, it's not just a dot in the center. If I turn the intensity up a little, I can see what looks like half of the infinite symbol emerging from the dot towards the top of the screen, so more or less a teardrop shape with the point being at the dot.
(where's the 'smashing my head into the wall' emoticon thing?? :( )
Brian
Do you get that when both channel input coupling switches are set to "ground"? And the scope is fully warmed up, and the "focus" knob is adjusted for the best focus?
If the above are true, then you could try adjusting the "Astig" astigmatism control slightly to see if it improves the shape of the dot, but try to remember where it was set before so you can put it back if you get no improvement.
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Do you get that when both channel input coupling switches are set to "ground"? And the scope is fully warmed up, and the "focus" knob is adjusted for the best focus?
If the above are true, then you could try adjusting the "Astig" astigmatism control slightly to see if it improves the shape of the dot, but try to remember where it was set before so you can put it back if you get no improvement.
TK,
Hopefully his "infinity symbol" goes away when he sets the input switches to ground. Regardless, I think he should stop tweaking his scope 'till he is a bit more comfortable using it, and actually knows what is and isn't working.
I thought he was able to produce a stable, dual channel display of the calibrator some time ago. He should get back to that point before moving on.
PW
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Sure, I can agree with that... but I also encourage experimentation when done in an orderly manner, with time to analyze the results of each change in a variable!
Meanwhile... on the issue of improper signal grounds and use of the "LINE" trigger source:
I've just shot another video demonstrating the use of the "LINE" trigger source to find and display line noise (60Hz hum) superimposed on a signal of interest, caused by improper or insufficient signal ground at the scope. This video will be ready to view in a few minutes.
Meanwhile, slightly off topic, here's my "scoposcopy" video on the basics of determining frequency of a signal using an analog scope, featuring the classic antique Tek RM503 precision low-frequency oscilloscope:
Frequency in Hz = 1/(period in seconds)
and of course
Period in seconds = 1/(frequency in Hz)
http://www.youtube.com/watch?v=teXXF0a_WoI (http://www.youtube.com/watch?v=teXXF0a_WoI)
(Apologies for the poor video quality, this was before I found the right transcoder to use with my camera... )
ETA: The Line Trigger/Mains Hum video is ready here:
http://www.youtube.com/watch?v=spGpBz4K8rU
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MarkE,
I think we should all just focus on getting Brian to the point where he can get stable, correctly triggered displays on his scope.
A bit of tilt is the least of his problems at this point.
In the last video of his scope in action, I wanted to turn off CH2, speed up the horizontal and adjust trigger level for a stable display. Looks like he had one of the channels vert. sensitivity cranked up much higher than the other (or different probe factor), horizontal sweep way to slow, and that it was not triggering. It has been some time since Brian has produced a video of a stable display, tilt or no tilt.
PW
His square waves were collapsing. High pass had a shorter time constant than one half of each cycle. Like you I thought that he had operation with the calibrator working. I think he just needs to learn some basic skills: read the manual and try things out with what he has on hand.
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What about that one trimpot he adjusted a little while back? I would have thought that you needed another scope to tune those if calibration was off.
I believe he said he did not turn it much but, could that small adjustment cause any of this? Maybe he could turn it back to about where it was?
Just wondering...most, if not all, of this is over my head.
I was blown away by TK's video of the weird shapes playing on his scope with the sound input. How he inverted and made a mirror image of that logo is beyond me. Unless, that is the way it is suppose to be?
Bill
ETA: https://www.youtube.com/watch?v=OxlCoKN4W7c (https://www.youtube.com/watch?v=OxlCoKN4W7c)
EEVblog made a similar video, and his logo is reversed also! Probably supposed to be that way then....
PS Dave said that Youscope was developed by a 15 year old kid a long time ago. Holy crap!
Dave also runs it on his digital scope and..he really has to play with it to get rid of the fly back lines. It does not look nearly as cool as it does on an analogue scope.
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It's interesting that Dave's Hameg analog scope shows the text backwards, like my 2213a does, but the Agilent shows it the right way around. I wonder why that is. I can't get mine to display the text frontwards by inverting the CH2 (y) channel, or by swapping L and R (this makes the text run up and down instead of across). So maybe he has a way to invert the CH1 (x) channel on the Agilent and this is the cause. It's a mystery to me for sure.
I'm also wondering if that's the best display that the Rigol could do. It's supposed to be able to do some huge number of waveform samples per second, I thought, so I expected the display to be better than that. Maybe he has the sample rate at some non-optimum setting for this file. Also it's rather surprising that he couldn't get audio output to speakers at the same time he was scoping the file from the output jack. I have no problem doing this with my desktop system. I suppose this depends on the headphone jack arrangement. Maybe his HP jack turns off the speakers; my front panel HP jack doesn't have to do that if I don't want it to.
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OK, I am taking a break from cleaning this nasty arse desktop PC to format and load Ubuntu on for the lab stuff, and all that... came back over to check the thread and :o
I made a list of things to try, and I am going to start with checking the ground for resistance/continuity,
then get it warmed up, set XY no input, set to ground, check focus, and tweak astig if necessary (no improvement, back to initial setting)
(start vid)
then do the LINE test using my PCFG w same sq wave settings as cal loop w/ 1 channel only.
then I'm going to put CH1 on cal loop, upper half to start, then add in the PCFG CH2 bottom half w/same freq etc (triggering off cal loop)
anything else?
Let me know if you think that the +55V rail that I adjusted per manual instruction (first part first section of calibration, I believe it is) is causing me these issues, or if you want me to set it back to 55.14V anyway and check. 'twould be easy enough if it may solve my issues.
so from my understanding of connections thus far, If my laptop had a ground on it's plug and a proper connection from charger to PC, I technically don't need to have the "reference" clip connected, is that right? If so, that would mean a laptop PC should be just fine for using as a FG when unplugged, even, as long as I have a good connection to the laptop's 'chassis' ground (or ground on HP jack collar, same thing) w/ the reference clip.
I will check back before I start the vid once I turn my laptop back on. Can't remove the battery for this test though, or I would do that, too, so there would be no power source other than the PC clock button cell on the MB.
You know, I vaguely remember actually getting fairly good looking square/triangle/sawtooth waveforms from the PCFG the first time I got the PCFG working..... I don't know what could have changed from then to now.. other than me. so I shall try this again from sq 1..
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It's interesting that Dave's Hameg analog scope shows the text backwards, like my 2213a does, but the Agilent shows it the right way around. I wonder why that is. I can't get mine to display the text frontwards by inverting the CH2 (y) channel, or by swapping L and R (this makes the text run up and down instead of across). So maybe he has a way to invert the CH1 (x) channel on the Agilent and this is the cause. It's a mystery to me for sure.
I'm also wondering if that's the best display that the Rigol could do. It's supposed to be able to do some huge number of waveform samples per second, I thought, so I expected the display to be better than that. Maybe he has the sample rate at some non-optimum setting for this file. Also it's rather surprising that he couldn't get audio output to speakers at the same time he was scoping the file from the output jack. I have no problem doing this with my desktop system. I suppose this depends on the headphone jack arrangement. Maybe his HP jack turns off the speakers; my front panel HP jack doesn't have to do that if I don't want it to.
TK:
I am glad you noticed that the lettering was correct on Dave's digital scope. I thought I saw that as well. My new pc, if using the headphone jack on the front, disables the speakers of which I am running a total of 11 including a sub. (All of my speakers except one pair have their own amps including a 100 watt/channel driving my 12" Cerwin Vegas in the living room.) I can take or tap into one of the line outs on the back and still hear the music.
What the hell is a flac file? I mean, I know what it is...I looked it up...but have not downloaded any program to open such a file. I have used some of the choices given in the past and, my problem is, they take over every audio file and you have to use their program to play anything. Should I just convert the youscope file to mp3?
I thought you would enjoy Dave's video on this. He really had to manipulate that digital scope to get it to look right, and it still did not look as good, in my opinion, as the older model, ha ha.
Bill
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No, I'd suggest you leave the +55 volt adjustment alone, until you go into the complete calibration procedure, which you probably don't need to do anyway.
The Astig control is easy to re-set if you change it for the worse and it's right there on the front panel. But again, I'd only mess with this if you actually see the "teardrop" dot in xy-mode when both channels are set to "ground" input coupling and the scope is fully warmed up, the dot is focused well, and the intensity is set to a reasonable, not overly bright level.
It is true that the mains-powered instruments are grounded back through the mains plug but it is not a good idea to depend on this for your signal ground path. (Even though it worked for the signal I was displaying on the LINE trigger video above... both the F43 and the scope are plugged into the same power strip and when I selected the non-isolated position on the FG it made the ground path connection through the ground prongs of the three-prong plugs and the power strip.) You should properly use short, direct paths for the signal ground just as you do for the signal itself.
The LINE trigger source setting is to see if you are experiencing some 60Hz hum, which might be due to improper grounding or high-resistance in the grounding. I suggested it because of the way the display was jumping up and down and seemed unstable otherwise in that video you posted.
The laptop's power supply will generally isolate the output to the laptop from the mains line plug, at least both of mine do. You can use your DMM to check continuity between the laptop-plug end and the mains cord prongs (unplugged of course!); I'll bet you do not have a proper path to the mains ground from the laptop's chassis through the power supply.
Yes, I think you will have to provide the proper ground connection to the laptop either way, whether the power supply is used or not, by clipping to the ground conductor of the headphone output jack which should be the outer collar, or to the USB jack's outer shield or similar chassis ground point. I just checked my laptops again and they are definitely _not_ grounded back to the mains through the power supplies. (an old IBM 600e and a newer Samsung netbook).
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TK:
I am glad you noticed that the lettering was correct on Dave's digital scope. I thought I saw that as well. My new pc, if using the headphone jack on the front, disables the speakers of which I am running a total of 11 including a sub. (All of my speakers except one pair have their own amps including a 100 watt/channel driving my 12" Cerwin Vegas in the living room.) I can take or tap into one of the line outs on the back and still hear the music.
What the hell is a flac file? I mean, I know what it is...I looked it up...but have not downloaded any program to open such a file. I have used some of the choices given in the past and, my problem is, they take over every audio file and you have to use their program to play anything. Should I just convert the youscope file to mp3?
I thought you would enjoy Dave's video on this. He really had to manipulate that digital scope to get it to look right, and it still did not look as good, in my opinion, as the older model, ha ha.
Bill
Well, you can use VLC to play the FLAC file, and when you install it you can choose not to make it the default player for all media files.
http://www.videolan.org/vlc/#download
But once you get used to VLC you probably will use it for everything.
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Well, you can use VLC to play the FLAC file, and when you install it you can choose not to make it the default player for all media files.
http://www.videolan.org/vlc/#download (http://www.videolan.org/vlc/#download)
But once you get used to VLC you probably will use it for everything.
VLC was one of the ones that took over my music collection. It added little cone icons to every file. I did not realize that I could stop it from doing so. I will give it another try...thank you.
Bill
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VLC was one of the ones that took over my music collection. It added little cone icons to every file. I did not realize that I could stop it from doing so. I will give it another try...thank you.
Bill
hmmm... the last time I installed it, as I recall it gave a list of media file types and asked if you wanted to make it the default player for them, and showed checkboxes that you could uncheck for each file type extension. Now you've got me worried. I can't find where to change the file assignments now either. So maybe you can just find the right decoder for your favorite player to play the FLAC files instead of screwing up your system by installing VLC. Sorry.... I forget that my favorite solutions may not work for everyone sometimes.
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WELP....
::)
Thanks TK for telling me to slow down, and PW for telling me to start back at square 1. When I combined both pieces of advice, I solved the issue...
It appears that my PC wasn't actually disabling the enhancements when I was telling it to, for some reason or another. So it was the "Loudness Equalization" enhancement that was causing all the trouble. I guess when I split up the HP jack and the main internal speakers, it disabled my ability to change those settings, even though it let me check/uncheck boxes and hit OK.... stupid computers.
https://www.youtube.com/watch?v=GKLZJ8hCClY
At 0:28 I say "microphone" when I meant Headphones.
Simple problem, simple fix. Now to figure out WHY my laptop didn't change the HP settings with dual outputs enabled!! (or maybe it even had something to do with me shutting off the PC for a few min, and then powering it back on... who knows.... maybe I didn't restart after installing Soundcard Scope, and it froze my audio settings?
my bet is that it had something to do with the restart, and I won't be able to get it to freeze my settings again.)
Sooooooo..... NOW to see if I actually see the proper visuals for Youscope & Oscillofun!!! ANNDD I can probably listen in, too!
Thanks for the always-good-advice, everyone!
Brian
I should have remembered this little trick from my PC repair/programming days..... if there's an issue and it involves a computer - RESTART THAT SUCKER FIRST!!!! hahha
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OscilloFUN! 8)
https://www.youtube.com/watch?v=YUlk-zwKfWo
Looks a whoooooole lot better now!
Hooked up a pair of old active PC speakers instead of the headphones, so you can actually hear it on the vid, too.
Other than being 90 degrees off, it looks like it should!
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WELP....
::)
Thanks TK for telling me to slow down, and PW for telling me to start back at square 1. When I combined both pieces of advice, I solved the issue...
It appears that my PC wasn't actually disabling the enhancements when I was telling it to, for some reason or another. So it was the "Loudness Equalization" enhancement that was causing all the trouble. I guess when I split up the HP jack and the main internal speakers, it disabled my ability to change those settings, even though it let me check/uncheck boxes and hit OK.... stupid computers.
https://www.youtube.com/watch?v=GKLZJ8hCClY
At 0:28 I say "microphone" when I meant Headphones.
Simple problem, simple fix. Now to figure out WHY my laptop didn't change the HP settings with dual outputs enabled!! (or maybe it even had something to do with me shutting off the PC for a few min, and then powering it back on... who knows.... maybe I didn't restart after installing Soundcard Scope, and it froze my audio settings?
my bet is that it had something to do with the restart, and I won't be able to get it to freeze my settings again.)
Sooooooo..... NOW to see if I actually see the proper visuals for Youscope & Oscillofun!!! ANNDD I can probably listen in, too!
Thanks for the always-good-advice, everyone!
Brian
I should have remembered this little trick from my PC repair/programming days..... if there's an issue and it involves a computer - RESTART THAT SUCKER FIRST!!!! hahha
Brian,
Looks like you are getting a stable display!!
It appears that you have stumbled upon one of the handy uses for a 1K square wave and a scope when doing audio testing.
A 1K square wave contains harmonics. A perfect square wave would contain an infinite number of harmonics, but for audio work, we usually figure the leading edge of a 1K square wave will let us see out to 10K, and that a 2K square wave will let us see out to 20K.
If you feed a 1K or 2K square wave into an audio system and adjust its equalizer (tone controls) at various frequencies, you can rapidly tell if the equalizer is working. For instance, a treble control when boosted, will create a peak at the leading edge of the square wave as the level of the higher frequency harmonics is increased (similar to the large peak at leading edge of the square wave in your video). Cutting the treble control will cause the leading edge of the square wave to droop, or round, as the high frequency harmonics in the square wave are reduced.
A midrange tone control will produce a hump or dip in the middle of the square depending upon whether it is boosted or cut respectively. A bass tone control will generally produce a left to right upward or downward slant of the square wave if boosted or cut respectively (sometimes you need to reduce the square wave to 100 to 500 Hertz to see the effects of a very LF equalizer that is centered at 50Hz or lower).
In your video, it looks like the high frequencies are being boosted quite a bit when your "enhancements" are turned on. Any audio played thru that setting would sound VERY bright.
A "loudness" control typically boosts the bottom end (low frequencies) of an audio signal (as well as some upper mid boost). Usually the lower the level control is set, the greater the bottom end is boosted when "loudness" is selected. Your waveform looks more like just high frequencies and upper midrange are being boosted. Possibly selecting a 100Hz square wave will allow you to see if the extreme LF is also being boosted, which would be indicated by the square wave tilting upward from left to right.
Try to ensure that all EQ and "enhancements" are turned off when using the PC FG so that the waveforms will look correct (flat frequency response thru the soundcard).
I sure like seeing your waveform lock right up when you tweak the trigger level control.
You're getting there...
PW
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OscilloFUN! 8)
https://www.youtube.com/watch?v=YUlk-zwKfWo (https://www.youtube.com/watch?v=YUlk-zwKfWo)
Looks a whoooooole lot better now!
Hooked up a pair of old active PC speakers instead of the headphones, so you can actually hear it on the vid, too.
Other than being 90 degrees off, it looks like it should!
That's great! It's actually one of the best displays of that file I've seen! This is actually the first time I've been able to see the full A T O M D E L T A letters so clearly, even if they are upside down (instead of sideways?) You could try inverting CH2 and see if the letters show right-side up!
Clearly there is nothing wrong with the major sections of the scope: input and display. I doubt that there will be any issues with timebase or trigger either.
You've got the L and R channels going to the wrong scope channels is all, just swap them and you'll see the display rotate 90 degrees to conform to what is usually seen. But before you do that try inverting CH2 !
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Brian, in the earlier video you are puzzled by the fact that at one point the scope still showed a horizontal line when you had no signal from the laptop going to it. Later on, the screen blanked when you had no signal. What was the scope control that you adjusted between those incidents? The scope's Trigger Level control. ;)
When it didn't blank, you had the trigger level set so precisely that it responded to the inevitable tiny noise left on the signal and showed you the baseline. Moving the control a tiny fraction either way would have caused the screen to blank. When you reset the trigger level later on, you didn't hit this exact setting, so when you turned off the signal from the soundcard the screen blanked as you expected it to. That all actually indicates _great_ trigger performance from a very sensitive trigger circuit.
:D
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Brian, in the earlier video you are puzzled by the fact that at one point the scope still showed a horizontal line when you had no signal from the laptop going to it. Later on, the screen blanked when you had no signal. What was the scope control that you adjusted between those incidents? The scope's Trigger Level control. ;)
When it didn't blank, you had the trigger level set so precisely that it responded to the inevitable tiny noise left on the signal and showed you the baseline. Moving the control a tiny fraction either way would have caused the screen to blank. When you reset the trigger level later on, you didn't hit this exact setting, so when you turned off the signal from the soundcard the screen blanked as you expected it to. That all actually indicates _great_ trigger performance from a very sensitive trigger circuit.
:D
TK,
Do you know if AUTO on Brian's TEK allows the scope to free run (display a trace) in the absence of a trigger (signal input)?
If so, he might be more comfortable using that mode instead of NORM.
PW
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TK,
Do you know if AUTO on Brian's TEK allows the scope to free run (display a trace) in the absence of a trigger (signal input)?
If so, he might be more comfortable using that mode instead of NORM.
PW
Yes, I believe it does.
Meanwhile, scoposcopy fans... check out Jerobeam Fenderson's website. Scroll down about half-way. See anything familiar? ;)
http://www.jerobeamfenderson.net/
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PW,
that's most definitely good to know. I'll remember that for the next time I set up an audio system.
That's great! It's actually one of the best displays of that file I've seen! This is actually the first time I've been able to see the full A T O M D E L T A letters so clearly, even if they are upside down (instead of sideways?) You could try inverting CH2 and see if the letters show right-side up!
Clearly there is nothing wrong with the major sections of the scope: input and display. I doubt that there will be any issues with timebase or trigger either.
You've got the L and R channels going to the wrong scope channels is all, just swap them and you'll see the display rotate 90 degrees to conform to what is usually seen. But before you do that try inverting CH2 !
I will most definitely try both right after I get this post typed up and see if I can get them to display right side up! If I can, I'll make another vid of it. I can actually make it look even sharper if I run it without an audio output. Seems I got a good scope! Must have been very well taken care of by the power company that had it for a while, and then when they got rid of it, it was rarely ever used at all from what I was told.
Brian, in the earlier video you are puzzled by the fact that at one point the scope still showed a horizontal line when you had no signal from the laptop going to it. Later on, the screen blanked when you had no signal. What was the scope control that you adjusted between those incidents? The scope's Trigger Level control. ;)
When it didn't blank, you had the trigger level set so precisely that it responded to the inevitable tiny noise left on the signal and showed you the baseline. Moving the control a tiny fraction either way would have caused the screen to blank. When you reset the trigger level later on, you didn't hit this exact setting, so when you turned off the signal from the soundcard the screen blanked as you expected it to. That all actually indicates _great_ trigger performance from a very sensitive trigger circuit.
Yep! I realized that afterwards, and noticed that when the trigger is set in a certain range, it is EXTREMELY sensitive. In that range, even lightly bumping the table, or setting something down will make it trigger.
TK,
Do you know if AUTO on Brian's TEK allows the scope to free run (display a trace) in the absence of a trigger (signal input)?
If so, he might be more comfortable using that mode instead of NORM.
PW
Yes, it most certainly does. Isn't it a good idea to keep it on NORM and get used to adjusting the tigger level? I'm sure there will also be some applications from time to time where I would want it on AUTO, so I will also set it on AUTO and repeat whatever process I had just done with it on NORM, that way I know what to expect with both.
Meanwhile, scoposcopy fans... check out Jerobeam Fenderson's website. Scroll down about half-way. See anything familiar? ;)
http://www.jerobeamfenderson.net/
It's allllmost my scope! that's the B model, though. Wonder what the difference is other than the button setup... looks like it's got a few extra knobs as well.
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What I usually do is to use Auto to set up baselines (channel input coupling to Ground) and V/div settings (input coupling to DC or AC coupled) and trigger slope (rising or falling edge) , then once I know I can get the trace at the proper vertical scale, I switch to Normal and use the trigger level knob to get a triggered trace when the signal of interest is applied. Then when I'm not probing anything the screen blanks. When I apply the signal the screen wakes up and shows the trace.
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That's great! It's actually one of the best displays of that file I've seen! This is actually the first time I've been able to see the full A T O M D E L T A letters so clearly, even if they are upside down (instead of sideways?) You could try inverting CH2 and see if the letters show right-side up!
Clearly there is nothing wrong with the major sections of the scope: input and display. I doubt that there will be any issues with timebase or trigger either.
You've got the L and R channels going to the wrong scope channels is all, just swap them and you'll see the display rotate 90 degrees to conform to what is usually seen. But before you do that try inverting CH2 !
!!!!!!!!!!!!!!!!!!!!!!! :D
https://www.youtube.com/watch?v=bOPaevLfGnc
I am downloading Ubuntu ISO for the desktop, and decided to do a search for Linux Oscilloscope and Function Generator, and found this:
http://www.filebuzz.com/findsoftware/Linux_Function_Generator_Sound_Card/1.html
click on the Oscilloscope and read the features of that! Not bad for $25, and the multiInstrument version has everything for $50. I may try and get that at some point if I'm able to get 2 input channels going via soundcard, and don't end up finding something similar for free. That's after I get some real hardware of course...
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What I usually do is to use Auto to set up baselines (channel input coupling to Ground) and V/div settings (input coupling to DC or AC coupled) and trigger slope (rising or falling edge) , then once I know I can get the trace at the proper vertical scale, I switch to Normal and use the trigger level knob to get a triggered trace when the signal of interest is applied. Then when I'm not probing anything the screen blanks. When I apply the signal the screen wakes up and shows the trace.
good stuff. I'll try to get in the habit of doing that.
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As a side note, I've had to go back to using an analog oscilloscope to analyses some noisy pulses. My $350 100mhz digital could not trigger or even see capacitively coupled spark plug coil discharges of my car. The old analog did it with ease. A friend of mine at a TV station told me the same story regarding a strangely modulated carrier and an expensive digital oscilloscope that was useless, whereas the old analog saved the day.
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As a side note, I've had to go back to using an analog oscilloscope to analyses some noisy pulses. My $350 100mhz digital could not trigger or even see capacitively coupled spark plug coil discharges of my car. The old analog did it with ease. A friend of mine at a TV station told me the same story regarding a strangely modulated carrier and an expensive digital oscilloscope that was useless, whereas the old analog saved the day.
TK has regularly commented on the limitations of digital oscilloscopes. Digital scopes do some great things, but they are very limited by the dynamic range of their ADCs and the capture rate of their triggering systems. Keysight makes a big deal about their custom ASICs that enable much higher capture rates of their oscilloscopes compared to competitors.
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Keysight makes a big deal about their custom ASICs that enable much higher capture rates of their oscilloscopes compared to competitors.
I am just guessing that this comes at a much higher price?
Bill
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I am just guessing that this comes at a much higher price?
Bill
Oh, nothing too extravagant, only a few thousand dollars minimum....... up into the tens of thousands.
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Oh, nothing too extravagant, only a few thousand dollars minimum....... up into the tens of thousands.
Ahh...I thought as much. Good to know it is available if needed but...I am happy with my 80's Tek scope for the time being. It will probably take me the rest of my life to outgrow this scope...maybe longer, ha ha.
Bill
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Oh, nothing too extravagant, only a few thousand dollars minimum....... up into the tens of thousands.
Or hundreds of thousands.
A 3000 or 4000 series DSO come in the price ranges you're talking about. If you want something that can look at 28Gbps signals, choose between a house and the instrument.
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Or hundreds of thousands.
A 3000 or 4000 series DSO come in the price ranges you're talking about. If you want something that can look at 28Gbps signals, choose between a house and the instrument.
My fault. I only looked at the first page of Ebay. I doubt they have any of the ones in that high a price range.
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Brian, I'd really like to see you measure some higher frequencies on the scope. The GenRad oscillator spec says it will go to 50 MHz. The problem with higher frequencies though is that proper connections and terminations will be needed for really good readings. But if you turn the output of the GenRad right down to minimum and use the 10x probe to connect to the GR RF output connector directly, then gently turn up the output of the oscillator, you should be able to display a signal at least. The period of a 25 MHz waveform is 40 nanoseconds, so the waveform should display nicely on the .05 microseconds/div setting of the timebase knob. It may take a few minutes for the oscillator to warm up properly and stabilize.
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Brian, I'd really like to see you measure some higher frequencies on the scope. The GenRad oscillator spec says it will go to 50 MHz. The problem with higher frequencies though is that proper connections and terminations will be needed for really good readings. But if you turn the output of the GenRad right down to minimum and use the 10x probe to connect to the GR RF output connector directly, then gently turn up the output of the oscillator, you should be able to display a signal at least. The period of a 25 MHz waveform is 40 nanoseconds, so the waveform should display nicely on the .05 microseconds/div setting of the timebase knob. It may take a few minutes for the oscillator to warm up properly and stabilize.
I was actually just reading the manual while waiting for the ol' lap PC to dl/install it's updates. To think I have to do it all again when I get an AMD SATA compatible PSU for the better PC.
Here shortly I will make a power cord for it and get things moving with it and make a vid.
According to the manual, I'm supposed to have a 500mA slow blow fuse for 115V power input and 250mA slow blow for 230V.. one of the fuses may be the correct value (it only says 250V on it, but looks thin enough to be the 250mA) and the other is marked 8A 32V, so I do not believe it has the correct fuses in it for operation... however, it does not say "115-230V" on the plate under the plug. It says "105-125V", so I'm not sure exactly what values it's supposed to have for it's two fuses, but I'm pretty sure that an 8A 32V is the WRONG fuse..
Do you think I would be safe swapping it out for a 500mA 250V? or better yet, start with a 250mA 250V fuse in that spot just to be safe? I don't want to run it without having it properly fuse-protected and blow the thing up!!
Ah, I see.... I am correct that it is the wrong fuse, and figured out why the plate only says "105-125V", and the fuse configuration. On page 10 of the 1330-A PDF, in the parts list, it states that for 115V operation, I am to use TWO .5A type 3AG fuses. If I were operating it at 230V I would be using two .25A 3AG fuses.... glad I checked them before doing anything else!! Hopefully I have a couple slow-blow 500mA's I can use!
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I ordered the fuses along with some other goodies from Digikey, so hopefully it will get here by Monday or maybe even Sat, and then I can start runnin some tests with the 1330A Oscillator!!!! :)
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A quick update on the status of the GR 1330-A to O-scope testing vid:
Acc to USPS tracking, my Digikey order with my fuses SHOULD be here tomorrow, so I am hoping that I will be able to start using the Oscillator at some point tomorrow and make an initial vid.
I say "SHOULD" because we have received around a foot of heavy snow here, and almost all of the roads are completely iced over with a thick later, so I'm keeping my fingers crossed that the trucks don't get delayed. As of now, according to their website, everything is on schedule. :)
Also, an off-topic comment: I have decided that my first REAL project (non ###### related) is going to be a crystal radio set with as many tunable components as I can make it (within reason). I have been studying up on how it's done, expected results per build specs, etc and feel confident that it's definitely within my skill set to do. The thread I have been reading/re-reading specific posts: http://www.overunity.com/15538/crystal-radio-the-first-real-free-energy-device/
This should be a great starting project for the Scope/Oscillator that I am currently learning to use.
Brian
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Hey there everyone,
My fuses FINALLY arrived, and my GR Oscillator seems to be working great! I have made a video while running thru a number of the various settings of the Oscillator. It's fairly long, especially since I didn't run any tests at all with it before making the vid. I apologize for the lighting (again), as I haven't managed to get a good setup in place with my mini-lab just yet. (Any suggestions for the type of lights I should install in my 3-lamp ceiling track light for this would be appreciated.)
https://www.youtube.com/watch?v=EPR4aRoIVPE
I still don't yet have the proper adapters for the Oscillator just yet, but hopefully will soon. I ordered some Hantek HT30-A cables and mini grabber attachments so far. Right now, on hand I have (2) T's, (4) F-F 75ohm adapters. I also have several compression BNC fittings and 75ohm RG6 coax that I can make some patch cables with. (I need to dig up some of my NOS RG-58 50ohm. - I'll order some higher quality ones once I have most of the other necessary fittings I need, or if I run across a cant-pass-up deal on some).
As for a list of fittings I still need to get: GR874 to BNC; 50ohm Terminators; BNC to Phono; 50ohm F to F; 50ohm M to M; BNC to SO-239/PL259; and good patch cables.
TK - is there anything I am missing in that list that you think I should get? What is your opinion on the broken panel mount GR874 fitting for RF on the Oscillator? Does it look like it may cause me issues, or should my connection strength still be OK for the time being?
I am taking my time building my variable capacitors (I'll probably still just order a couple from that site that was suggested in that thread), so I'll likely just build the Variometer that you made and use some fixed capacitors for now. Other than that project, what do you suggest I do for a good project to enhance my learning experience with the oscillator and/or scope?
Brian
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@Brian: Congratulations on getting the GenRad oscillator up and running!
Some comments:
Determining frequency: Millisecond or ms is 0.001 second. Microsecond (Greek letter "mu" which looks like a "u") is 0.001 ms or 0.000001 second. Nanosecond (ns) is 0.001 us. (I always remember "nanosecond" because "nan" sounds like "nine" : 0.000000001 second (nine decimal places)). And frequency is 1/period, and period is 1/frequency. So if your timebase is set to 1 ms/div (0.001 sec/div), then the middle 8 divisions of the graticule indicate 8 ms (0.008 seconds) of time, and if you have, say, 12 complete cycles in that time, your frequency is 12/0.008 or 1500 cycles per second, ie 1500 Hz. I use the middle 8 graticule divisions because this is where the sweep will be most accurate wrt the actual knob setting. ("var" in the cal detent of course). The 1000 Hz setting of the audio output looked right on, it was putting every peak exactly on a graticule line when you had the timebase set to 1 ms (0.001 sec) per division.
The broken GR connector: the determining factor here will be to see if it still mates properly with another GR connector, like when you get your GR-BNC adaptor. It probably will but I can't tell from the video whether the damage is severe enough to prevent proper connection. Somebody probably twisted when they should have pulled, or something like that. If it doesn't mate properly with another GR connector then you have a couple of options. You _might_ be able to find a replacement bulkhead-mount GR connector for replacement -- this will preserve the authenticity and collectability of the unit. Or you could remove the connector and replace it with a panel-mount BNC connector and a bit of aluminum sheet to fill the gap. This might be the cheapest way to go but it might offend the true General Radio aficionados.
The modulation: Hmmm.... when you were connected to the "Audio" output jack it looked like you were seeing the RF superimposed on the audio modulation signal. I kept wanting you to turn the timebase down to 1ms/div so you could see the audio. The scope was triggering on the audio rather than the RF within the audio. Once you changed to the RF output jack it looked more normal to me. It looks like the oscillator and scope are both working perfectly. The sine wave is a little distorted but not too bad.
Nice work! I'm glad to see that nice old oscillator working properly.I don't have any specific suggestions at the moment but if I can think of any I'll let you know. Cheers!
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@Brian: Congratulations on getting the GenRad oscillator up and running!
Some comments:
Determining frequency: Millisecond or ms is 0.001 second. Microsecond (Greek letter "mu" which looks like a "u") is 0.001 ms or 0.000001 second. Nanosecond (ns) is 0.001 us. (I always remember "nanosecond" because "nan" sounds like "nine" : 0.000000001 second (nine decimal places)). And frequency is 1/period, and period is 1/frequency. So if your timebase is set to 1 ms/div (0.001 sec/div), then the middle 8 divisions of the graticule indicate 8 ms (0.008 seconds) of time, and if you have, say, 12 complete cycles in that time, your frequency is 12/0.008 or 1500 cycles per second, ie 1500 Hz. I use the middle 8 graticule divisions because this is where the sweep will be most accurate wrt the actual knob setting. ("var" in the cal detent of course). The 1000 Hz setting of the audio output looked right on, it was putting every peak exactly on a graticule line when you had the timebase set to 1 ms (0.001 sec) per division.
The broken GR connector: the determining factor here will be to see if it still mates properly with another GR connector, like when you get your GR-BNC adaptor. It probably will but I can't tell from the video whether the damage is severe enough to prevent proper connection. Somebody probably twisted when they should have pulled, or something like that. If it doesn't mate properly with another GR connector then you have a couple of options. You _might_ be able to find a replacement bulkhead-mount GR connector for replacement -- this will preserve the authenticity and collectability of the unit. Or you could remove the connector and replace it with a panel-mount BNC connector and a bit of aluminum sheet to fill the gap. This might be the cheapest way to go but it might offend the true General Radio aficionados.
The modulation: Hmmm.... when you were connected to the "Audio" output jack it looked like you were seeing the RF superimposed on the audio modulation signal. I kept wanting you to turn the timebase down to 1ms/div so you could see the audio. The scope was triggering on the audio rather than the RF within the audio. Once you changed to the RF output jack it looked more normal to me. It looks like the oscillator and scope are both working perfectly. The sine wave is a little distorted but not too bad.
Nice work! I'm glad to see that nice old oscillator working properly.I don't have any specific suggestions at the moment but if I can think of any I'll let you know. Cheers!
TK,
Thank you, I have been wondering how exactly to calculate frequency from traces. I knew generally how it was done from your videos, I just didn't know the exact numbers and specific method. I copied/pasted that section to Word, enlarged text, and am printing it off so I can reference it every time until it's memorized.
The GR connector: hopefully it does mate well with another 874 with the two broken prongs. Unfortunately, instead of the broken prongs being opposite each other, they are one of each vert and horiz. The bottom and right prongs are broken off all the way in to the plastic backing piece. At some point, even if it is operable, I would like to replace it anyway, but hopefully I can do it some other time when I am more comfortable disassembling it to get to the connections properly. If it does cause issues with another GR fitting, what about soldering directly to the remaining tabs with a short, thick lead and going to a panel mount BNC for the time being (until I obtain a proper replacement 874)? Or do you think that may cause various issues such as excessive leakage RF at higher frequencies?
The MOD: I will make another video and connect to the audio jack with RF output, leaving the scope on 1ms/div and see what we get. What do you think may be causing the distortion? the cheap probe, lack of proper connections and termination, or something else? I ordered some terminators along with BNC-Phono, and some realllllly good long minigrabbers I found for a great deal from Vetco.net. If you haven't found that site quite yet, please take a look and let me know what you think of their goods and if they appear to be of good quality, or of cheap Chinese manufacturing origins. Of course the best way to find out will be when I receive my goods in the mail, but I found the exact grabbers on ebay that someone was selling for about $9 each, when they are only $2.69ea there. Here's a link to the grabbers I scooped: http://www.vetco.net/catalog/product_info.php?cPath=41_438&products_id=6944
Do you think I did the right thing by waiting until I had the proper fuses before operating it? I feel like I left you waiting for a demo far too long, and possibly made you think that I'm not really interested in learning how to use the scope and my equipment. I assure you that is not the case! I may get a little too excited at times and get a bit ahead of myself (like I did with building my own var-air-caps, which are a big PITA - but I'm not giving up on!!) and then calm down and come back to full reality later, but when I decide to start something I always follow thru. I just wanted to clear that up, since I kind of got the feeling that you thought you had possibly wasted some of your time instructing me. I really do appreciate the guidance, and any way I can get you back for the help, I will, so just ask anytime and if it's something I'm capable of or something I have, I'll happily assist or send it your way. Currently my main expertise relating to what's done in this field is designing and building mechanical related things, and woodworking.
Anyway, in your opinion, above what frequency should I need to be using a termination setup to get proper output signal/measurements? Do you think that 75ohm coax is worth making any patch cables out of, or do you think I should just wait until I find my RG-58? I may just go to the store and buy a 25 or 50 foot RG-58 cable and chop it up so I have some patch cables for now til I get some better ones. I don't like spending money on low-mid quality goods like that, so I'd like to wait until I find a good deal on and can afford to get a set of high quality patch cables. Kind of like I did with my T's - I got a pair of new Amphenol's for 3 bucks. Those are fairly decent, right? If not, I only spent 3 bucks anyway, haha.
Saludos!
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Frequency is just the inverse of time period. You can find the time period by counting off the number of divisions a complete cycle takes and multiplying that by the time period per division. Divide that into one second and you have the frequency. A scope sweeping at 5us per division and 10 divisions across the screen takes 50us for one pass. A waveform that is exactly one cycle per screen is: 1/50us/cycle or 20k cycles per second. If two cycles complete each screen then the frequency is 40kHz. If five cycles complete, then it is 100kHz, and so on. If one waveform fills 3.5 divisions, thent he frequency is: 1/(3.5*5us)/cycle or 57kHz.
For decent coax and sinewaves: 20MHz*meters will be OK. IE if you have a 10MHz signal a 2 meter unterminated coax won't cause much distortion from the reflections. For squarewaves, 0.4ns/cm = 1ns/inch rise or fall times will be reasonably clean. Modern logic like DDR3 has rise and fall times down to around 50ps - 70ps which demands termination in almost all applications. Stuff like common CMOS logic is much slower and can go a couple to several inches without termination cleanly.
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For decent coax and sinewaves: 20MHz*meters will be OK. IE if you have a 10MHz signal a 2 meter unterminated coax won't cause much distortion from the reflections. For squarewaves, 0.4ns/cm = 1ns/inch rise or fall times will be reasonably clean. Modern logic like DDR3 has rise and fall times down to around 50ps - 70ps which demands termination in almost all applications. Stuff like common CMOS logic is much slower and can go a couple to several inches without termination cleanly.
MarkE -
So if I want to test the max output of my oscillator (50Mhz), I should use the shortest possible coax direct into my scope (I do not have any in-line attenuators yet), preferably around 15.6 inches or less? (Just a guess here, but preferably I would use a tee connection with one side going directly into a 50ohm terminator and a 10:1 or 20:1 attenuator between the tee and the scope, so I don't have to max out my time/div to .05us . Am I correct?)
What you are stating with square wave with fast rise/fall times applies when I am using a direct connection to scope and not a probe?
Once I actually receive at least the terminations, and make some decent patch cables, I will experiment further with these setups and compare probe use to direct connections with the PC signal generator and the oscillator. Should I find a pair of, or at least one 20:1 attenuator as well, or is that not necessary for the time being?
TK (and all),
What are your thoughts on this GR974 - BNC adapter?
http://www.ebay.com/itm/BNC-TO-GR874-COAXIAL-CONNECTORS-WITH-16-BELDEN-WIRE-RG58A-U-/291176479245?pt=LH_DefaultDomain_0&hash=item43cb787a0d
I personally do not like the crimp connection at the BNC, but the main thing here is just getting a GR874 connector. I can always replace the BNC fitting, shorten the cable, or possibly even replace the RG-58 cable with something better if it becomes necessary at some point. I would rather get a GR to BNC direct one piece, but everyone is wanting upwards of $30 for a single unit..
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MarkE -
So if I want to test the max output of my oscillator (50Mhz), I should use the shortest possible coax direct into my scope (I do not have any in-line attenuators yet), preferably around 15.6 inches or less? (Just a guess here, but preferably I would use a tee connection with one side going directly into a 50ohm terminator and a 10:1 or 20:1 attenuator between the tee and the scope, so I don't have to max out my time/div to .05us . Am I correct?)
What you are stating with square wave with fast rise/fall times applies when I am using a direct connection to scope and not a probe?
For sinewaves the signal is narrow band and we can talk about the signal frequency. Yes, if you do not want to see significant distortion from an unterminated 50MHz signal then you don't want a propagation path longer than about 1/10th the period: 1/10th * 20ns = 2ns ~1.25' or about 15 inches. It is not as though at 15.1" you will have a problem. But you will get a very rude surprise at a quarter wavelength.
Things won't be too bad using a BNC T right at the scope that has a 50 Ohm terminator on one leg.
Once I actually receive at least the terminations, and make some decent patch cables, I will experiment further with these setups and compare probe use to direct connections with the PC signal generator and the oscillator. Should I find a pair of, or at least one 20:1 attenuator as well, or is that not necessary for the time being?
Attenuators have limited usefulness. They can be useful for limiting reflections. Your 465 limits you to 100MHz, so I don't think reflections are going to be your biggest headaches. Sometimes a 2:1 power divider is a handy thing to have around. With one of those you can fire off a signal to a DUT and monitor the original signal on your scope without distorting it.
TK (and all),
What are your thoughts on this GR974 - BNC adapter?
http://www.ebay.com/itm/BNC-TO-GR874-COAXIAL-CONNECTORS-WITH-16-BELDEN-WIRE-RG58A-U-/291176479245?pt=LH_DefaultDomain_0&hash=item43cb787a0d
I personally do not like the crimp connection at the BNC, but the main thing here is just getting a GR874 connector. I can always replace the BNC fitting, shorten the cable, or possibly even replace the RG-58 cable with something better if it becomes necessary at some point. I would rather get a GR to BNC direct one piece, but everyone is wanting upwards of $30 for a single unit..
With shipping this used unit is going to cost you $15.00 It looks serviceable.
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@Brian:
This should be a suitable replacement for your panel mount 874 connector:
http://www.ebay.com/itm/GENERAL-RADIO-GR-874-PB58-CONNECTOR-NEW-/121589661784?pt=LH_DefaultDomain_0&hash=item1c4f4f0058 (http://www.ebay.com/itm/GENERAL-RADIO-GR-874-PB58-CONNECTOR-NEW-/121589661784?pt=LH_DefaultDomain_0&hash=item1c4f4f0058)
This place has a bunch of 874 fittings, etc but I didn't see the precise panel mount connector listed, you may want to call them to see if they have the exact replacement:
http://www.mgs4u.com/RF-Microwave/General-Radio-GR-874.htm (http://www.mgs4u.com/RF-Microwave/General-Radio-GR-874.htm)
If I were you I'd stick to 50 ohm co-ax and the BNC connector system for all Ts, terminators, attenuators, patch cords and other fittings, and just get the one necessary 874-to-BNC adaptor for the GenRad oscillator itself.
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@Brian:
This should be a suitable replacement for your panel mount 874 connector:
http://www.ebay.com/itm/GENERAL-RADIO-GR-874-PB58-CONNECTOR-NEW-/121589661784?pt=LH_DefaultDomain_0&hash=item1c4f4f0058 (http://www.ebay.com/itm/GENERAL-RADIO-GR-874-PB58-CONNECTOR-NEW-/121589661784?pt=LH_DefaultDomain_0&hash=item1c4f4f0058)
Yep, that's the exact one that the manual specifies as it's "Panel Mount Connector". I did not see that listing when I first searched.
If I were you I'd stick to 50 ohm co-ax and the BNC connector system for all Ts, terminators, attenuators, patch cords and other fittings, and just get the one necessary 874-to-BNC adaptor for the GenRad oscillator itself.
That is the plan. When I said "Replace the BNC connector" I meant replacing the crimp-on BNC with a Solder-type or Compression-type BNC fitting. From my experience with cable and satellite systems, crimping, crushing, or even sometimes squeezing a coax cable can cause distortion to the signal. This occurs mostly with digital signals, but just the fact that it can distort a signal at all makes me not want crimp fittings for anything. Not only that, but they aren't very secure. One good yank and the connector could come right off.
As for the 'making my own patch cables' - the only reason I am planning on doing this for the time being is that I have a surplus of compression BNC fittings, the coax strippers, and compression tool to do it all. I have thousands of feet of RG6 that I can't use, but RG58 is pretty cheap. I could make 12 2' cables for the cost of one actual patch cable, plus I can make them custom length so I don't have a bunch of excess rolled up. If I had to buy everything, I would just buy a couple pairs of cables instead.
I was playing with my Arduino a little earlier in preparation to build that Inducto-meter. I built the I2C LCD interface and found out that the coding in the sketch is apparently incorrect... and I have no idea how to fix it. So I guess until I learn how to write code for it, or someone else fixes it, I will be using the multiple wire LCD setup. I did notice that with that specific IC I can run up to 8 LCD's off of the same two wires by just assigning different addresses. I'm assuming I could easily add a piezo instead of one of the other screens. That would bring me up to the Parallax's capabilities for much cheaper than $45. I'll figure out the coding issue in the next few days hopefully.
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Well, well, well..... It appears that Mr Tek decided to start acting up again....
Everything has been fine and dandy up until today, when Channel 2 decided it didn't want to trigger above the .2V/div (on 1x, 2V/div 10x) setting.
I have been using it a bit probing around on various circuits, and never had any problems at all, until I got this FG today and started testing it out.
This is where things went wrong:
At first, I was comparing the MAIN output (on CH1 scope) to the TTL output (CH2 scope) for a while, and playing with the sweep settings on the Tek CFG253. At this point everything was fine.
Next I disconnected from the Tek and connected up to the Wavetek 166. I tested it out a bit on only channel one for a while, and then hooked up TTL to channel 2 of my scope, and that is when I noticed something was wrong with Channel 2. I then disconnected everything, went back to the Tek 253 and hooked up the MAIN to CH1 and got it displaying a waveform. I set CH2 of the scope to the exact same settings (above .2V/div) and switched my BNC from the MAIN of FG to CH2, and could not get it to trigger and display the waveform. When I put it on AUTO I get a nearly flatlined trace, and cannot get a stable trigger at all. :(
I could just leave it like this, and only be able to use CH2 for up to 16V max with a 10X probe, but who wants to have a piece of equipment that they can't use the full range of features on?? Not me! If I can't solve this, it's going to drive me nuts! I'm going to look thru the troubleshooting and schematics of the manual and see what I can figure out here after I make a video to show what's happening. For now I really just wanted to get this info out here to see if anyone has any ideas that can help me get a bead on what's wrong here.
A video demonstrating the problem using a small device and also a function generator:
https://www.youtube.com/watch?v=YGbAhnIFfeU
Thank you for all of your help everyone! You've all gotten me this far in such a short amount of time, which is incredible. Hopefully this problem can be resolved fairly easily and the full functionality of this scope restored.
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Wellllll,
I am looking at the schematic for the CH2 vertical preamp and my assessment is that the X100 attenuator is blown. I don't know how I did it, but I must have. I am attaching a picture of the internal settings for the CH2 V/div knob, and you will notice that above 500mV/div and above use the X100 attenuator. nothing below that does. This makes perfect sense, now just to find the part. I'm almost 100% certain that this is it, so if anyone would be able to confirm this for me, I'll just order the part instead of even opening up the scope and looking around in it.
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I am just going to post this for future reference for anyone who may end up having the same problem.
I correctly diagnosed the problem I was having with channel 2 above 200mV/div - It was in fact the X100 attenuator, and replacing that part did fix the problem.
I am thinking that this may have been the faulty part that was spoken of when I acquired the scope, and it had just enough life left in it to get me thus far on a good cleaning before blowing. (since after doing some researching on no-no's with Scopes, I have found none that I may have done).
Also, since I still had "noise" from my vertical position knobs after my previous cleaning attempts (especially channel 2), I decided I would take care of that while I had it opened up.
- I loosened the 4 screws on the back of the pot case just enough to be able to shoot some LPS inside of it. I gave it a shot, worked the pot back and forth a few times, then gave it another rinsing shot, and tightened the screws back up. This solved that problem entirely. Now when I adjust the vertical position, even if I turn the knob quickly, I don't get a bunch of scratchy lines across my CRT. ::thumbs up::
That is all...
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I am just going to post this for future reference for anyone who may end up having the same problem.
I correctly diagnosed the problem I was having with channel 2 above 200mV/div - It was in fact the X100 attenuator, and replacing that part did fix the problem.
I am thinking that this may have been the faulty part that was spoken of when I acquired the scope, and it had just enough life left in it to get me thus far on a good cleaning before blowing. (since after doing some researching on no-no's with Scopes, I have found none that I may have done).
Also, since I still had "noise" from my vertical position knobs after my previous cleaning attempts (especially channel 2), I decided I would take care of that while I had it opened up.
- I loosened the 4 screws on the back of the pot case just enough to be able to shoot some LPS inside of it. I gave it a shot, worked the pot back and forth a few times, then gave it another rinsing shot, and tightened the screws back up. This solved that problem entirely. Now when I adjust the vertical position, even if I turn the knob quickly, I don't get a bunch of scratchy lines across my CRT. ::thumbs up::
That is all...
Good work.
Don't feel bad about having probs with a used scope. TK just received a brand new 4 channel digital scope and has problems with channel 4 right out of the box. Of course, his is still under warranty but, what a pain in the ass.
Bill
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Yep, had to send it back to the vendor, and they've sent me a replacement, due to arrive tomorrow.
Here's the video I made documenting the main problem with the channel 4 :
http://www.youtube.com/watch?v=7RvcByoEE5o
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Good work.
Don't feel bad about having probs with a used scope. TK just received a brand new 4 channel digital scope and has problems with channel 4 right out of the box. Of course, his is still under warranty but, what a pain in the ass.
Bill
Yes, that is very unfortunate. Very few, if any companies make anything with the same care and at the same quality level as they used to. Also, the more functions that are added to something, the more "components" there are to be broken. (I quoted that since it technically speaking has less actual components due to ICs) Also, it becomes that much harder to repair since so many things are packed onto a single semiconductor device.
This is why I have been tossing around the idea of buying a used, time-tested digitizing or digital phosphor oscilloscope.... but then again, if I were to buy new and had an issue, I could just send it in under warranty, and buy an extended-extended warranty.
Considering the point I am at in my electronic education, I think it's better if I don't have a scope that does all the math for me.... A freq counter, pencil & paper, and my brain need their workout!!
TK - Let's all hope that they send a delivery driver that can pick the correct house this time - or that they reamed the idjjot and he doesn't make the same mistake twice. I'm sure you'll be doing what I'd do, and continually check the tracking status! haha Let's PRAY that this scope doesn't have ANY issues at all this time! Or ever, for that matter!
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Yep, it supposedly is on the local brown truck for delivery today --- sometime today. The last one was dropped off around 7:30 pm, at the wrong house next door.
I spray-painted our house number on a big piece of cardboard and put it on the front porch.... maybe that will help the driver get oriented...
I'm watching the front-porch security cam on the computer, watching for the Brown Truck... yesterday I saw them about 6 times driving past on the street, haven't seen any yet today. I'm afraid to go make lunch, might miss something while I'm in the kitchen.
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I don't blame you. On the days that I was expecting an equipment delivery I actually stayed home just to make sure I was there to get it as soon as it arrived, and I kept checking for it outside and constantly reloading the tracking page.... and I will be doing this again on Sat or Mon for my freq counter. I live directly off of a high traffic state road, though, so it's doubtful anyone would be bold enough to steal something off my front porch or garage door. Ya never know, though. I'd be even more anxious if I were waiting on something like your scope!
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What frequency counter did you wind up getting?
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Tektronix CMC251. 1hz - 1.3Ghz w/ precision 10Mhz reference oscillator (and self-check function). :)
I don't know if it has the Ratio A/B function, but it appears to be very close to mint condition like the CFG253, it's from the same seller, and I got quite a deal on it. I d/l'ed the Manual, but still didn't catch anything on Ratio, but didn't fully go thru it yet.
I think the ones they had donated to them like these Tek's may have been some university's property that were tucked away somewhere as spares. The top of the CFG253 had sharpie on it of some stock-type designation number, there is zero wear on it, but a few of the push in-out type selector buttons have a whiter area on top from where they had been left pushed in for such a long time. They are evenly toned, which leads me to my conclusion of university back-stock - rarely - if ever used prior to initial testing.
I've got my fingers crossed that the counter is the exact same. :)
It's a TCXO not an OCXO, but it's probably the closest I'll get to super-ultra precision for under $100 and in (hopefully) fantastic condition.
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Good find, sounds like you got a good deal. Unfortunately it does not have Ratio A/B, but it does have Period and Totalizer functions.
Here's what it looks like inside:
http://www.eevblog.com/forum/testgear/tektronix-cmc251-frequency-counter/
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Good find, sounds like you got a good deal. Unfortunately it does not have Ratio A/B, but it does have Period and Totalizer functions.
Here's what it looks like inside:
http://www.eevblog.com/forum/testgear/tektronix-cmc251-frequency-counter/
Wow, nice! I think mine came from that exact same lot! haha It's from Talahassee FL Goodwill and I paid $70. It wasn't listed as "for parts.." though. However it did say "used - power tested - no further testing" - which was the status of the FG I bought from them of the same Tek line. It seems they also think that they came from a school of some sort over there at EEV.
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The CMC251 made it here in one piece via USPS this morning - 3 days early. :) They did MASH the corner of the box, but thankfully it was correctly packaged so it didn't harm the gear. It's in the condition I expected - the same as the CFG253 - working, no signs of actual use, and just a little discoloration on top of a few buttons (from storing).
TK - I see that your scope FINALLY made an appearance! Congrats! I hope your blood pressure stabilized finally! Also hope that it works 100% no issues at all this time.. It sounds to me like UPS in your area just does not give a rats arse about customers... I'd be calling the BBB and also getting on the UPS website and opening several cases/filing complaints! MAYBE corporate will get on your local center over it and fire that P-O-S driver!!
But anyway, I'm looking forward to some vids! :)
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This pup is dead-on! Precisely 10Mhz! :)
Well, according to the resolution of it's display, which, at X100 gate is to 1mhz.