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Author Topic: Test Equipment: Oscillocopes  (Read 42420 times)

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #60 on: February 21, 2015, 12:34:43 AM »
Ah OK, now the video link shows as "being processed".

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Re: Test Equipment: Oscillocopes
« Reply #60 on: February 21, 2015, 12:34:43 AM »

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #61 on: February 21, 2015, 12:38:58 AM »
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...





Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #62 on: February 21, 2015, 12:41:08 AM »
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.

Offline MileHigh

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Re: Test Equipment: Oscillocopes
« Reply #63 on: February 21, 2015, 01:05:40 AM »
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

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #64 on: February 21, 2015, 01:12:08 AM »
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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Re: Test Equipment: Oscillocopes
« Reply #64 on: February 21, 2015, 01:12:08 AM »
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Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #65 on: February 21, 2015, 01:25:35 AM »
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

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #66 on: February 21, 2015, 01:25:41 AM »
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....

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #66 on: February 21, 2015, 01:25:41 AM »
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Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #67 on: February 21, 2015, 01:44:54 AM »
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.

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #68 on: February 21, 2015, 01:52:43 AM »
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.

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #69 on: February 21, 2015, 02:15:16 AM »
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/

Free Energy | searching for free energy and discussing free energy

Re: Test Equipment: Oscillocopes
« Reply #69 on: February 21, 2015, 02:15:16 AM »
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Offline MileHigh

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Re: Test Equipment: Oscillocopes
« Reply #70 on: February 21, 2015, 02:16:22 AM »
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.

Offline MarkE

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Re: Test Equipment: Oscillocopes
« Reply #71 on: February 21, 2015, 03:50:11 AM »
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.

Offline TinselKoala

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Re: Test Equipment: Oscillocopes
« Reply #72 on: February 21, 2015, 03:57:17 AM »
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.

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #73 on: February 21, 2015, 05:35:29 PM »
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?

Offline Brian516

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Re: Test Equipment: Oscillocopes
« Reply #74 on: February 21, 2015, 05:36:48 PM »
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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Re: Test Equipment: Oscillocopes
« Reply #74 on: February 21, 2015, 05:36:48 PM »

 

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