I don't know how to proceed other than to check pin one on the tube socket and check for continuity each end of the wires or just replace the pot if I can find a equivalent part.. The sharp control is also another issue, the wiper and one of the end terminals are bent into each other on that pot and soldered to each other and goes to ground, pot measures very low ohms and meter doesn't go up/down at all the way it's set up, but according to the sams, this is the way that pot is..
