Hi all,
I am a high school senior in the US and I started making a DRSSTC back in January 2020, taking inspiration from Mads' DRSSTC I. I made the oneTesla kit a number of years ago and decided to come back to the wonderful land of Tesla coils. I have also made a spark gap tesla coil, which can be seen off to the right in the video below. Working on and off during the coronavirus lockdown, I had my first successful test last month (200VDC bus from variac): It blew right after I took this video, which I attribute to my poor bridge design: https://drive.google.com/file/d/1YcG2pWm8kf7eFIVq646JIEfXXsDc9pin/view?usp=sharing. Whole rat's nest of wires. I have since remade the bridge with IXXN110N65C IGBTs and busbar, found here: https://drive.google.com/file/d/1Ah39WuPqT2fYzhU6FvLrx1yl8nClExOo/view?usp=sharing. Since making the new bridge, I have not been able to get it running. New MMC is 3x7 CDE942C20P15 for 0.35uF @ 6KVDC, or around 900VAC derated @74kHz. Bus is 15,000uF 400V Kemets(2 x 7,500). Driver board is a variant of oneTesla's: https://drive.google.com/file/d/1pFHJJzeRBw8jN1Er48E7NNonjFVLksk1/view?usp=sharing. I use a 15v 1:1:1:1:1 GDT, something I plan to change in the future. I also added an OCD circuit after blowing the first set of IGBTs, which is not shown on the schematic. For an interrupter, I used oneTesla's SD interrupter. It's designed for much smaller coils, so I plan on modifying that in the future as well, but it works for now.

After firing up the new coil last night, no sparks flew. I have been stuck scratching my head. I was running with 130VDC from a variac. I tried flipping the feedback CT, but still no luck. I did notice, however, that the MMC gets charged, which is curious (After signaling the coil to fire and nothing happened, I shut everything down and measured a quickly declining voltage across the MMC). Any thoughts/comments/suggestions on what to try next? If you have any clarifying questions, please let me know and I'll try to get back ASAP.