Hallo again.

I still get at point B the same value with point A.

Well, i tried with
1. no de-qing diode,
2. other MOT as charging coil, i tried with open/close primary coil of the charging trans.
3. Smaller Cap at the end (5nF)

I also tested without cap, and still the reading after the charging coil is 2,2KV. The same as at point A!!!!!

Do you think that i have to ground something at this schematic? I just grounded the PCB input Line filter and limiter! Nothing else!

Tnks

FWB consists of 24 X 4007 diodes. Each diode has a voltage rating up to 1000V.

I just tested it again by the help of an oscilloscope. FWB work as expected. A rectified signal at 100HZ. Capacitors smooth it at a decent level. RMS is 2,2KV. Then i connect the charging coil and the final capacitor and nothing changes!!! Nothing at all! Is there any possibility to need more inductance? I am thinking to try two mots at series as a charging coil. Any other ideas?     

Hi Jeg and Tinsel, It is strange that the charging circuit is not working, again Tinsel is correct, if the charging circuit is not working there must be a problem so disconnecting it might show where the problem is. I would take a picture of my primary circuit but it is quite busy under the coil and would be difficult to trace the wire's and bits. One problem with using a MOT for a charging inductor is that the secondary is connected to the core/body of the transformer so the entire MOT core is at HV, I had to raise mine up off the wood base and sit it on wax blocks otherwise it arced into the wooden base and lost power but still tried to work, the other option is to disconnect the end of the secondary connected to the core but I don't think that way is without problems.

I didn't get the the charging circuit working properly until I used the rotary spark gap so that I had a reliable break rate. Your kinda jumping in the deep end using a charging circuit in a medium powered transformer as a first attempt. The charging inductance is related to the break rate and the HV caps it charges. It's a "Dark Art" with few hard and fast rules. The best way to gauge output voltage is to setup the circuit without the charging inductor or the De-Q-ing diode but with a safety gap across the Power MOT secondary about 1.5 to 2 mm and set a small working gap but keep increasing it till it stops and the safety gap fires, then add the charging inductor and de-q-ing diode and see if the working gap fires, when you can get a 3 or 4 mm spark on the working gap but the safety gap stops firing and is smaller then you know the charging circuit is increasing the voltage to the HV discharge caps. The actual gap in the spark gaps needs to be adjusted to "conditions" there is no actual distance can be given only approximate.

Open circuiting a MOT can damage the insulation if high enough voltages are reached, safety gaps prevent that happening, but using only one MOT the gaps will fire from HV to ground which I don't like to do, my gaps go from HV positive to HV negative not to ground. Is it possible the MOT insulation is damaged and the inductor is not really being utilized.

The charging circuit needs to have a certain amount of inductance, it is a bit flexible and it can work without the de-Q-ing diode but won't work if the FWBR is kaput or if the charging coil is shorted internally, diodes do weird things and they can test OK but not work properly, these circuits are hell on some parts and at times momentary currents can get to ridiculously enormous magnitudes.
I can't even test a Microwave oven diode, my DMM just says it's open circuit, if it showed a short then the diode is busted, but in between open and shorted funny things can happen also.

I use Microwave oven diodes for the FWBR and then I use two microwave oven diodes in series for the "De-Q-ing" diode. I found when the charging inductance was not enough
the supply can drive the primary directly through the spark gap which seriously heats the FWBR diodes as well as other things and uses a lot of power.

Just now I am not prepared to use my coil, I'm right out of space and the ground is dry as can be, if I fire up the coil with no ground connected it rattles the sub woofer connected to my computer by way of signals through the built in amplifier in the speaker system.   I won't use it unless I get good ground conduction. It'll rain within the month.

Don't allow it to frustrate you, you'll get where your going if you remain safe. Safety first, fun second.

Cheers

Thanks Jeg for making the measurments again. It sounds like the basic DC power supply is working without major problems. I would still recommend going to a higher current diode than the 1n4007 though, because of heat dissipation and safety margin. The 6A100 is very common, you should have no problem finding them. But don't stop work while you are waiting, keep going with the "current" bridge, haha.

Next step is to put the de-Qing diode in. That is your MO diode, right?

I really don't think you will be happy using a simple automotive spark plug for your spark gap. I could be wrong, but I think it is likely that you will get a power arc across the gap instead of an interrupting spark. You could try blowing it with compressed air if it turns out that the power arc is a problem.

Here's a photo of a simple multi-element spark gap that might work better than a simple automotive spark plug. I would suggest using 4 tubes to start with, each screwed thru the center as shown, and positioned close together. The resulting gap can then be adjusted by turning the tubes around the screws, so that the tubes are still parallel but closer or further apart.
||||  furthest apart, or //// closer together, get the picture?
So the end tubes are connected to the circuit, the two middle tubes are "passive" and you have three spark regions.

http://www.coe.ufrj.br/~acmq/tesla/mres4gap.jpg

I'll be making one like this to try on my MOT-DC coil fairly soon.

This is very smart! Do you think that a pipe system doesn't need air blowing? What kind of metal is the best for sparks? I mean is there anything that last for a long time without getting black and carbonized?

A good multi-element gap shouldn't need quenching with compressed air, but you still should have some ventilation. The sparks make nitrogen oxides from the air and this isn't good to breathe. Most people use copper pipe because it is cheap, available and easy to work with. You will have to clean the electrodes of any spark gap you build, even if you use tungsten or something like that, but it's easy enough to do.

And there is something else that i always wonder about. Are Tesla Coil discharges harmful? If a long spark from the top of Tesla coil find your hand will it harm you?

A properly running low power Tesla coil's output is a clean sine wave oscillation at a high frequency. This has two effects: First, the nervous system doesn't respond to high frequencies so you won't feel a "shock". Second, the power travels over the skin rather than penetrating deeply. This means that you can take the discharge safely, but NOT DIRECTLY TO THE SKIN because you will get a bad RF burn at the point of contact. However you can hold a wrench or screwdriver firmly in your hand and then let the spark go to the wrench first and then you won't feel it at all. This isn't harmful.... IF the coil is working properly. If there is a short to the primary supply, then DANGEROUS voltages at the low frequency of the mains supply can be mixed with the Tesla discharge and this is VERY dangerous. So for larger coils, for questionable builds or coils that might not be running perfectly... don't do it. I've gotten a couple of bad RF burns. Even small ones are very painful and take a long time to heal.

I used to do a demonstration with my big 2kW class traditional SGTC, with rotary gap and neon sign transformer primary supply. This coil would make a thick ropy arc 18 inches long into a big wrench that I held in one hand. My other hand held one terminal of a small 15-Watt 120V light bulb. I could touch the other terminal of the bulb to another person's skin and the filament would glow brightly.
I was a lot more confident and less careful in those days ! But it was actually fairly safe to do that.

The coil I show in the video below gave me a bad RF burn one day when I reached out and touched the secondary just above the primary winding. There is less than 100 volts DC being switched in the primary!  I thought it would be OK to touch it so low on the secondary but I was wrong. It cooked a pea-sized chunk of meat in my finger, all the way to the bone, took weeks to heal and I still have the scar from it. Even just above the primary winding, the secondary was already making enough voltage to penetrate the insulation on the wire and there was enough power there to cook my finger instantly. I felt that, all right!

http://www.youtube.com/watch?v=UFHNY38GQsI

This is an early demo of a low-power run of a solid-state TC. The boring stuff in the first five minutes can be ignored. I show some power arcs and wood burning to demonstrate that there is power and heat in the discharge, then I let it discharge into a small metal screwdriver that I'm holding.
I am not confident enough to try this with full power in my blown MOT-DC coil but I've done it with the SassyClassE SSTC.

And I would not recommend trying it on a MOT-powered coil, or ANY coil, unless you are absolutely sure of two things: It must be _impossible_ for any of the primary tank supply to be directly connected to the secondary output discharge in any way. You have to be very careful about this because the primary can spark to the secondary down low where you might not be able to see it and this can mix primary tank current into the secondary discharge. Second, make sure the coil's output is "clean", a sinusoidal oscillation at the resonant frequency with not much distortion or noise.

I don't recommend this at all, actually. If you do decide to take a Tesla Coil discharge into your body, even from a small coil, you are RISKING YOUR LIFE if something goes wrong, and MOT powered coils are especially dangerous because the MOT does not  limit current in the same way that a NST does.

Nice work guys and cool videos! HV is dangerous but so fascinating! 

Well, i tried almost everything to double the voltage but nothing. The only thing i didn't try is to disconnect the input pcb which was taken from a microwave oven. It suppose to be just a line filter and an inrush current limiter! How can this affect the output? Anyway. I am thinking to built Farmhand's circuit for 8000V. Two mots input, middle ground output, and charging coil after rectification.

If i use copper for spark gap then what the color of the spark would be?     

Hi Jeg, L2 and L3 are just extra coils they aren't really necessary, L4 is the main charging inductor, it's the MOT secondary and the frame will be "hot" because it's in an active line. I just put the L2 and L3  coils there of a millihenry or few every bit helps I guess, as long as it's thick wire, that is because being less inductance they will not increase too much the voltage so mustn't waste power either. I think even MOT primaries would be too much, I don't even think my coils are 1 mH.  Good job getting two in anti parallel anyway.

Now with the MOT for the charging coil, you can set it up on something that is a good insulator so it does not arc into the table and back to the supply/circuit ground, I had mine on a wood base that also had the power MOT's screwed onto it and the charging MOT arced into the wood which drained my power a lot. I had it screwed in to the base as well so I didn't see it until I tested it.

I wouldn't think the line filter would limit anything. Unless it's damaged maybe. Is it fused ? Try a different fuse maybe if it is.

Can you show a picture or a drawing of your circuit now ? Even the two MOT's in parallel should work a gap Ok but you'll want some restriction of current I agree.

One other thing is that with a charging circuit to get it going on a static gap it might be necessary to halve the spark gap distance because no doubling will occur until after the first cycle is finished maybe two cycles.

Tesla used a static spark gap with one electrode one electrode that was movable so he could tap an insulated extension of the electrode to "narrow the gap to start the process. With the rotary gap I can have a very small gap and it makes it work, I adjust it so that when the electrodes heat up the almost start to touch and sometimes do.
The less the gap the less the resistance of the gap. Another reason rotary gaps are good. But a static will work if the process is started somehow. If the gap is too narrow to start with and fixed so it works straight away the extra voltage would maybe cause power arcing in the gap

With a well setup air blown gap the gap can be small and blown after starting to prevent power arcs in the spark gap.

I hope we can help you sort this out. 

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