best mosfet config for a powerful flyback driver? would a capacitor across the flyback windings improve preformance?

well i have an instructable on my singing arc project, i tried the simple 555 driving a power mosfet, but they kept burning out. even the IRF840!!! rated for 500V!!! what am i doing wrong?


i tryed using a neon lamp with a series resistor of 4.6K ohms (i think) but it didnt help at all, in fact, it wouldn't even light, yet i got a nasty shock and 2mm spark from the 555 timer, i was amazed that it survived, but not for long, anyways.

so i moved on to try a fast diode across the primary, but backwards, to absorb the back-EMF. but it just cut away at the output significantly (from an 2 cm to less than 5mm). it got quite warm in the process too, for the few seconds it was on.

i havent tried it yet, but would a diode in series with the power supply, mosfet, flyback, and ground work better? and give a place for the electricity to go? what would a capacitor across the primary do? i heard people doing this and increasing the output, but will it impair an audio signal?

Picture of best mosfet config for a powerful flyback driver? would a capacitor across the flyback windings improve preformance?
schematic singing arkjpg.png
flyback driver mosfet section revision 1.png
Take an look at my latest "Instructable", a primer on the flyback circuit.

https://www.instructables.com/id/Flyback-transformers-how-and-why/

Thanks for reminding me to finish it.....