Help! My Coil Blew Up

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net> 

I built Justin and Arons Quasi Self resonant coil, and it blew up Friday
night.
Two mosfets failed. One was shorted and the other blew to bits. Even before
it blew up I was only getting 8" stremers out of it with 130 volt input, and
the fets ran hot. I checked the phasing of all the driver coils and
everything looked right. The thing that was really disturbing was that I was
getting ringing on the output of the H bridge even with a light bulb as a
load, and 12 volts pure DC on the rails. Some pics of the coil, and
waveforms can be seen at http://community.webshots-dot-com/album/113763981zJBnik

Well anyway, the two mosfets that shorted were not supposed to be on at the
same time. The two that were bad would have placed a short right across the
DC buss. The other two tested good. It appears that the driver survived all
this mayhem. It puts out a good waveform with only the good fets connected
to it. So at 8:15 PM, the cause of death was determined to be shoot
through. Now I had 10 ohm resistors in series with each gate with the
schottky across each one. It did improve the waveform, so the only thing to
do now is try and improve the layout of the GDT and MOSFETs.

I re-read the HV Guys instructions, and realised that I messed up big time
with the antenna. They say to put it no closer than 20" from the secondary,
and I had mine maybe 6" away, so maybe having it too close may have
introduced parasitics, or some other bad noise into the system. I also used
13 turns on my GDT instead of 10 like they suggested. With my resonant
frequency being around 236 KHz, which is a little on the high side, I could
probably do better with less turns on the GDT. I also noticed that they
don't have a toroid in their photos. I used one because Dan's SSTC had one,
but his circuit is also completely different than this one. Are Toroids bad
with this design?

Has anyone else had problems with shoot through or cross conduction?

If anyone can offer me any further insight, or suggestions, I would really
appreciate it!

Thanks,
Sue