28-08-2015, 10:26 AM
I've noticed a similar thing with the popular "Allan Bradley" potentiometers that were fitted to many sets during the 1970s. 50k was used a lot by Hacker, and they usually measure about 65k these days. Not a problem for the operation of the volume controls, but interesting nonetheless...
When these go bad, the problem is usually corrosion of the "wiper", but not the part that contacts the carbon track, but the part that contacts the metal track that is connected to the wiper tag. I did take some photos of the last one I did. I repair them by swapping parts from similar potentiometers - I look out for all examples of these, whatever the track value, because they are so easy to take apart and swap parts.
When these go bad, the problem is usually corrosion of the "wiper", but not the part that contacts the carbon track, but the part that contacts the metal track that is connected to the wiper tag. I did take some photos of the last one I did. I repair them by swapping parts from similar potentiometers - I look out for all examples of these, whatever the track value, because they are so easy to take apart and swap parts.
