Ampeg G110 Hum / no signal

[52 Bill]

The "gain control" mini-variable resistor measures 1.3m out of circuit, but while measuring the the voltage on either side of it it stays constant 16v across the entire range of the resistor. Am I correct in thinking that this controls functions of the reverb as well?

The reverb drive signal is sent from the emitter of Q2, so yes the gain control will affect the drive signal going to the tank.

The voltage on either side of the gain control will not change that much as it is being fed voltage from the output of the first chip as well as the bias supply line. The volume control seems to be wired as part of the feedback loop for the first IC, so the gain control fine tunes the maximum resistance of the volume pot which in turn sets the maximum gain of the stage.