Wayne Parham Messages: 18789 Registered: January 2001
Illuminati (33rd Degree)
It may be that the volume potentiometer is broken. I've seen them do this - the substrate cracks from repeated heat cycles of just old age. The wiper still works, and so there is still some variable resistance but if the crack is right on the junction to the ground side, then it isn't acting like a voltage divider anymore, just a variable series resistance. That causes the volume knob to still work, but only partially.