I purchased this amp off eBay as a repair/resell item. The listing claimed the amp had terrible output distortion. With the bottom plate removed, I examined the PCB and found a broken primary wire on the smaller transformer. Not uncommon for this type of break, this transformer is not mounted or secured to the PCB.
The wire break was too short to push into the solder hole, so I removed the transformer to repair. I did not want to unwind a loop, that may have changed performance, so I extended the wire.
I reinstalled the transformer and applied E6000 adhesive to secure the transformer to the PCB. This will prevent another break.
The amp powered up and passed a clean signal through to the output. All channels were tested and performed as designed.