Help with old Peavey CS400 power amp

[Cobbler]

I recently pulled my old band PA out of storage and have been performing clean-up and maintenance on all of the gear after years of heavy road use and just as many years of idle storage. Simple cleaning seems to be taking care of most of the issues and almost everything is up and running as it should.

The only piece of equipment with remaining problems is a very old (pre- DDT compression) Peavey CS400 power amp. Driving it hard, it displays no problems whatsoever and works as it should. At very low volume, one channel cuts in and out with a loud noise both when it comes and when it goes. The noise is similar to when you accidently turn on or off a piece of equipment upstream that is plugged into a powered up amp.

A couple people have told me that as long as it works at high volume levels, then there really is no problem. There may be something to this theory but I'd like to at least have the option of running it at a lower level like it should.

To me, this seems like a bad connection somewhere. I opened it up did a bunch of cleaning (there was some mystery fluid that had long ago leaked into it and pooled in the bottom of the chassis that I cleaned out) and now it's better but still not 100%. Am I on the right track chasing down connections?

[Gtr_tech]

Check for cracked solder on the boards. Clean/reseat any socketed op amps. If those have that molex header pin setup, those can become problematic, so clean and check the solder on both ends.

[Cobbler]

Check for cracked solder on the boards. ..... If those have that molex header pin setup, those can become problematic, .....

That's what it was. One of the pins where the driver board mounts had a broken solder joint. Works like a brand new amp now!!!

Thanks!