Persistent trouble with Keenwood KA-5500

Hello Agoners,

I have been experiencing an issue that seems difficult for the repair folks I use to isolate and repair.

UP FRONT:

It is not dirty pots or switches. These are clean as a whistle. No scratchiness, or dirty contacts. Please don’t say, "Clean the volume pot." It has been tested and works fine.

THE SYMPTOMS:

When I first turn the amp on, no sound until I crank the volume knob. Then it blasts on and I turn it back down. No scratchiness, just normal loud music. At that point it often works well for a bit, then sometimes, one channel will cut out, I crank the volume again, and it usually comes back. Rinse and repeat.

SO FAR: I have had it recapped, cleaned, output transistors replaced, and some broken solders repaired. 

I SUSPECT: More cracked or bad solder joints? Does this make sense? It seems like if i push enough powerl through by cranking the volume, it may be enough to bridge a bad connection, but when it cools off it gaps again. 

I am not an expert by any means, but is this a thing? Or is there another likely souce for this kind of issue?

If anyone has had similar issues, I’d love to know what the solution was. I’d like to keep the unit, as it’s pretty much the ony vintage-ish bit of kit I have left. I am willing to spend a bit to get it going "reliably" again, but maybe it’s not worth a huge expensive repair. Sounds great when working, though.

Any experience with this, or thoughts about how to address the issue?

Thank you!