You know those nice old ball handle switches... with the old brass patina of age on them? You just HATE to change one out with any modern appliance switch and loose that original look.
Well, you don't need to ! Just shoot some WD-40 (or similar electrical cleaner/lube) into the face area where the ball socket is. Push on the handle so the ball backs up from the face and the liquid can get inside. Then, work the switch many times. It will restore to working order about 80% of the time !
Remember, NEVER use any lubricant type spray on a band switch or a tube socket (can cause arcing on either). Use an evaporating cleaner like D5 Deoxit or various types by other brands.
For frozen vol or tone controls, spray the shaft/bushing area where the retainer clip is and apply heat from a solder pencil to the bushing. Turn the control clockwise usually to free it (or, better, check the resistance to see which way the wiper can be rotated safely without breaking it). This also works about 80% of the time.