[Tubesforme]

I restored a Philco Model 21, which has a late Model 20 chassis. The original volume control was badly rusted and wouldn't turn. I obtained a replacement that was the very same make and style as the original and it tested good and turned freely. I opened the back and cleaned it with DeoxIT D5, before installing it. The radio played great and continued to do so for a number of weeks. then it began acting like a noisy volume control does. I took the chassis out of the cabinet and cleaned it again. Same thing happened again. This time it played great for a couple of months. Cleaning the control returned the radio to normal, but I have never had anything like this happen to any other radio I have restored and the problem is happening again. All parts and tubes test good. It is only the control gets noisy. Has anyone else had any experiences like this? If so what was the solution? Thanks guys.