OK. Lots of stuff to look over.
most of these in good condition look like new from the bottom!
Old Electrolytic capacitors can be troublesome though.
Sometimes the bias supply filter caps can be going bad. That will cause the negative supply voltage to drift closer to zero and create an under biased condition. If so, you’ll never be able to dial in enough negative voltage to bring the idle current down.?
Re-capping the regulator power supply board is pretty easy to do. Just remember that the bias supply is all negative voltage and the positive legs of the capacitors are at ground potential.?
Bruce Collins