The easiest thing to do is exchange volume control with one of the two tone control in the same harness. I seldom use the tone control that is in good condition. It may be a little dirty but can be cleaned with a quality cleaner made especially for volume controls. I would ask a electronic supply house for the best chemical to clean the volume controls. You can visit a television and radio repair shop and they can help you.

If you want to keep the original solder joints the following can be of help. I have removed the “can” from the bottom of the potentiometers and taken out the carbon wafer and exchanged it with the needed potentiometer. Try experimenting with some old pots and see what they look like inside. Some are easily removable and other may be more difficult.