Origineel bericht door: Brett Hartt ,
My guess is that the contacts on the wheel have either corroded or been built up with dirt. Pull the wheel off of its peg, and unscrew the washer holding it in place (a pair of pliers will get it open). Open the back case with a Phillips screwdriver, and pull out the variable resistor. If you look at the underside of the resisitor mechanism, there are four metal tabs. Bend them out of the way, and lift the cover off. Inside are some metal rings, these are the contacts. You can clean them with some rubbing alcohol, or remove them and brush them down with some steel wool to remove corrosion. Good luck, let us know how it works out.