Andrew Gabriel wrote:


* A couple of years ago, I was breadboarding a circuit which used
a couple of power MOSFETS directly switching mains. As a temporary
measure, I used a bulldog clip to clamp a MOSFET to an aluminium
heatsink. When I got to adding the second MOSFET into the circuit,
I clamped that to the same heatsink. It was only after all the
testing when I was disassembling the breadboard circuit in order
to make up the real thing, that I suddenly realised that I'd had
full mains voltage between the two mounting surfaces of the MOSFETS.
The thin layor of aluminium oxide which inevitably forms on the
heatsink was all that stopped it going bang!



Yup. I done that, tho it was only 120v DC across it...