solid state amplifier making noise!


2011-08-24 11:26 pm
Hi, an old "Pearl SB 0-61" guitar and bass amplifier that my sons band had borrowed for practice has been returned to me, but it has been sitting for a while after one of my sons mates pulled it apart to find out what was rattling in side. He found the offending object a pair of scissors that had somehow ended up on the speaker magnet. Anyway I have just put it back together (put the chassis back in the box and the box back in the road case.
When I turned it on there was a lot of quite loud noise pop and crackle and squelching which settled down and was playable until the next time I turned it on the noise was back worse then ever and was independent of the volume knob and most controls accept for the bright switch which seems to make it change but not for better or worse.

I have pulled out the chassis and inspected the caps which all look fine, no bleeding or bulges. cleaned all the pots and contacts that link the circuits.
This amp has two circuit boards and what I think is a large finned heat sink.

Any help or advice on how to debug will be much appreciated.