Customer explained they accidentally wired the amp power terminals in reverse; B+ to GRD and GRD to B+. This immediately created a reverse connection to all the PS FETS source-drain resulting in damage to some of the FETS, half the drive circuits and damaged the PCB. Customer elected not to repair and abandoned the amp.
I opted to pull and replace all the PS FETS, all the drive BJTs and gate resistors, essentially rebuilding the power supply. I cleaned the soot from the PCB and repaired a burnt trace on the top of the PCB.
Next I repaired the burnt trace on the bottom of the PCB. To bridge the connection, I used solder wick to repair the connection bridge.
I soldered in the new parts and verified connectivity from the PWM driver through to the PS FETS, verify B+ and GRD as well as any shorts. All connections checked out.
I powered up the amp on low V to verify operation. Amp built rail voltages and the output began to isolate. While running on low V, I checked for hot spots. Finally, I powered the amp on full power and checked for proper operation. Amp output a correct waveform