Customer has (2) of these amps in for repair, this write up is for the 2nd amp.
Customer acquired this amp and explained it was known to be blown and not working. With the bottom plate removed, I checked the output FETS and found no defects. I then checked the power supply and saw obvious defective FETS and soot on the PCB. I found most all FETS were shorted, the driver circuit BJT mostly shorted, and most of the gate resistors open or out of tolerance.
I also saw, on some of the transformer secondary windings, small cuts exposing the wire, weird. This may have been what caused the PS to fail.
I removed the secondary windings and wrapped heat shrink over the exposed wire.
Then I removed all the failed parts and cleaned the PCB of soot.
Next, I soldered in the new parts including the PS FETS, gate resistors, output drive BJTs and their associated resistors.
Amp powered up, built rail voltage and the output began to oscillate. Amp was tested for heat spots, correct wave forms and proper output signal.