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# Can anyone help with troubleshooting a tesla coil?

After working on a tesla coil off and on for a few years I finally finished building one, but it is running into several problems. The only problem that I can't figure out is that despite following the basic tesla coil diagram the toroid will not create a jumping spark; however the gap generator still produces a spark. The coil is running off of a 15kv nst with a gfi built in.

## Discussions

1 year ago

So, I have hooked up my transformer to the spark gap and capacitors as shown in the figure and as soon as I hook it up to the capacitors, nothing happens and I get a quiet clicking noise from the transformer. It is a 12kv, 35mA transformer. What is happening?

4 years ago

Basic Tesla.

When you approach Resonance == the GFI will trip because resonant current is 5x to 10x the GFI limit.

Answer 4 years ago

Care to say if your basic is like this basic ??

Answer 4 years ago

Yes, that is the same diagram that i used.

Answer 4 years ago

You have to disable that GFI.

Answer 4 years ago

The only thing is the gfi does not trip even when the gap is going consistently.

Answer 4 years ago

I understand the GFI is not the problem.

Next, have you tried to change your capacitor 11 or 10 or 9 or 8 or 7 or 6 ?

The strategy is to find a resonance point by tuning the capacitor value.

Answer 4 years ago

So you are saying to take capacitors out until the system works?

Answer 4 years ago

Yes.

To get resonance, the inductive reactance needs to match the capacitance.

So, step change your capacitance and you should eventually discover your Tesla resonance point.

Be sure to have a small ( short ) spark gap for a start.

Answer 4 years ago

How short is short, an inch, half an inch, a centimeter, a millimeter? And thank you so much for consistently answering my questions.

Answer 4 years ago

Try somewhere about 1/16", 1/8", 3/16"

Answer 4 years ago

BTW when the GFI trips you will know you were near or at resonance.

Answer 4 years ago

Thank you, I will check it when it is no longer raining here!

4 years ago

Are the coils in resonance?

If the top load matched to the secondary in capacitance?

What is the size, number of turns and so on?

Without details it seems to be impossible to troubleshoot....

Answer 4 years ago

It is about 6.5 primary, and 600 on the secondary. We made the capacitors from snapple bottles so I do not know how to check their capacitance. I also do not know how to check for resonance.

Answer 4 years ago

In my old days of experimenting I did this with my big coils:

Make sure the capacitors are rated for the voltage, purpose and have a proper size that should match your system - if in doubt check Google for similar ones and how much capacitance was used.

Assuming a fixed spark gap and not a motorised one create the primary coil with enough turns so you can tap into different spots.

As the capacitor on the spark gap does not change you can change the frequency by tapping into different spots on the primary.

Once you found the point that gives you the biggest sparks (please turn off when changing the spot!) do some finetuning to get the sweet spot.

If it does not work this way you either have a too small capacitor bank or the topload is of the wrong size.

For basic testing you can start without the topload and just a pointy piece of wire sticking up.

Answer 4 years ago

So what you are saying is that i should get as large of a spark in the gap going as possible?

Answer 4 years ago

Not really, the gap distance is important too but that is in the region of finetuning once working properly.

You have to check the input for the primary:

Let's say you are now connected to the center and at the end of turn 22.

Change it to the end of turn number 21, then 20, 19 and so on.

If nothing changes when you reach turn number 8 you either have a problem with your setup or need more turns on your primary so you can go to 23, 24, 25...

Answer 4 years ago

The thing is the coil I built had at most seven turns on the primary, and just as a note it was based on this: https://www.instructables.com/id/How-to-build-a-Tesla-Coil/

Answer 4 years ago

oh and we did a 15 kv nst and 12 capacitors.