[smirnoffdear]

>> the relay that I said earlier it didn't have had its contacts welded together meaning the magnetron was energised constantly until the thermal cutout cut out.

That'd be the resetable on the mag heat fins.

Relays do weld sometimes with high start surges and faults, and age, you get a point that fits into a hole eventually.

I'm trying to remember the interlocker switch config, and reckon they drop a short across the line in case of some fault that'd have the mag running with door open, but can't be sure if this includes mag running with door shut when some fault of control board or relay. I think it probably does include the latter, so what you may have had was a faulty interlocker operation or slow moving switch, in which case a short may weld the relay. So you may have pulled a MWO to bits that initially had a faulty door interlocker, I can't be sure and would have to go dig out a road map to be sure..