Power rockford bd 1000 problem

I would start by replacing U21.


These amp tend to whine or ring from the toroid, epoxy or silicone will fix that.


If the noise is coming from the speaker when hooked up, check pins 1 and 7 on all the op-amps (TL072C) in the input stage. There shouldn't be any dc on these pins.


Is there any DC voltage on the output terminals?