Cannot find that 20mm long screw lurking anywhere and extremely unlikely to
jump through the grommeted lead ports into other section of amp and then
fall out. Straight on , top and bottom x30 viewing of all TO220 soldering
looks ok, surprisingly. Did find some nasty rework/fudge. 2 standard radial
legged 10uF 50V, C19 and C54 soldered to standard SM pads, no thru board
holes. Near it a SM cap, C61 measuring 15.2nF, had been soldered over
conformal coating with one end not soldered to trace, as coating under.
Owner has owned from new. 4x IRF450N power FET for 600W ?