Huge issue with the driver board

[MarcusFunt]

Hi

I am experiencing some bizarre problems regarding my gate drivers

I made a quick video, showing the problem with some waveforms.

To clarify. My drivers gave me an asymmetrical ac voltage+the on-times are really uneven, I get weird oscillations on the primary of my gdt, and I get large voltage spikes at the output of the gdt.
 
I tested the driver with 100khz even though I'm gonna run the coil at 350khz(I don't have a function generator, and the 555 wouldn't run stably on 350khz)

I'm using the attached schematic for my coil. no changes whatsoever.

Any help would be very much appreciated, I'm really stuck on this project 

[davekni]

Scope the input to your driver from your 555 signal generator (top of 1k antenna input resistor).  If that looks good (50% duty cycle), move to HC14 pin 1, then pin 2, pin 4, etc. through the driver circuit.  See where it gets distorted.

If you need more detailed help, please post still images and write questions in post text.  Scope screen captures (including volts/div and time/div) and still pictures of your setup are much easier to analyze.  Label where scope probe(s) are connected for each scope capture.

Good luck with debug.

[MarcusFunt]

Hi

I am starting to think that my board works fine because this is how the input signal looks.
(I was probing where the antenna is supposed to be connected)

[MarcusFunt]

okay here is the input to the 74hc14 (I'm sorry for spamming, but I haven't figured out how to put in pictures)

[MarcusFunt]

here is the output from the 74hc14

[davekni]

I am starting to think that my board works fine because this is how the input signal looks.
(I was probing where the antenna is supposed to be connected)

Clearly the issue is with the incoming signal.  You will need to modify your signal source to output 50% duty cycle.

okay here is the input to the 74hc14 (I'm sorry for spamming, but I haven't figured out how to put in pictures)

Since the antenna input is not 50% duty cycle, of course everything after it won't be either.

I had the same issue with attachments initially.  After you attach the first image, there is small text under where the file was selected that says "(more attachments)".  Click on that and it will add another line to insert a second attachment.  "(more attachments)" can be clicked as many times as necessary.

Thank you for the static images, including volts/division information.  Would help to list horizontal time/division too, in post text if not in image.  I presume 5us/division based on you saying 100kHz signal.

[MarcusFunt]

Thank you for your help 👍

Should i just give it a test with the transistors and coil attached?

[davekni]

Thank you for your help 👍

You're welcome.

Should i just give it a test with the transistors and coil attached?

That's your choice.  There's always a tradeoffs between spending lots of time testing components vs. testing whole system.  If everything is working, any time testing individual pieces is unnecessary.  However, if parts aren't working correctly, there's more chance of damaging components from a full-system test.  True for almost any system, not just Tesla coils.

If you set interrupter duty cycle very low, there is less risk from testing whole system.  Any stress on IGBTs will be short with plenty of time to cool down between bursts.