Originally Posted by
KVThere
I don't know if you solved the problem or not. I can suggest the following to aid in troubleshooting.
Disconnect the bridge rectifier from the secondary of the transformer (push on tabs). Turn on amp. If hum still there it is the primary windings that are loose and vibrating (not much to do about this). If hum gone, turn off amp and reconnect rectifier. Disconnect the positive and negative leads on the PS large caps that go to the boards. Turn on amp. If hum gone possible bad caps or big load on PS. Turn off amp. Reconnect PS Caps and disconnect + and - leads to boards. Turn on amp. Hum gone- problem is on boards causing big pull on PS loading transformer causing hum (normal). Hum still there bad caps (and or rectifier).
Hope this helps