Well, the eye protection worked, but note to self: Next time, wear ear protection too. Discharging 500v, 2500uf of capacitors through two mosfets makes a loud bang. I think the microcontroller crashed because of all the interference when I tried to measure that side of the H bridge through an oscilloscope. Got the output voltage up to 100VAC though, with 500vdc on the capacitors. Well time to buy new mosfets and hope that the driver ICs are still all right.