Putting my deer-stalker hat on. Someone had been inside to replace the
fuse. Left out some of the screws, including one self-tap that holds the
IEC. If that one was previously missing and the IEC just "held" by the
remaining one next to the TOP heatsink,loosened by repeated IEC
insertions AND the sillypad was punctured or close to puncturing. Then
the drummer tripped over the lead, IEC twisted and the IEC holding screw
touched the heatsink, as it is long enough, then blown TOP244, but about
4mm gap to swing across to do so. But as there are no pcb standoffs to
chassis in that area, relying on the IEC screws to chassis, then perhaps
the whole pcb being tilted in a downwards sense, by drummer standing on
the lead, and then only that arctan(2/20) 2mm gap for heatsink to
contact chassis.