I did try the fix from CL770 before but it did not work for me. As for the potentiometer, I found a couple of very similar Piher models that are 4.7 k ohms on the Mouser distributor website. I'm not familiar enough with electronics specs to figure out if either of them would work though. Piher offers the PT15 potentiometer in long life versions. I think they are 10,000 and 100,000 cycle rated.