Original post by: Fred ,
I have an older amplifier (which is what your volume knob controls) that has the same problem. It's as Markus says. There are dead spots on the potentiometer from corrosion. I have repaired them, myself, but it will be easier to replace. You decide. You will have to open the receiver, access the pot, desolder and remove it, then open the pot. This is the hard part, since it was never intended to be repaired. Be careful how you open it, or it will never look the same. There is a wiper arm that is moved across a series of ridges, which is just resistive wire wound around a core. The way to remove the corrosion is to burnish both the wiper and the resistor face with emery cloth. Reassmble and reinstall. Now, since you've destroyed the pot, search the internet (eBay, etc) using the part number off the case of the pot (I hope you saved it).