[Radioroslyn]

More than likely the volume control is worn out and needs to be replaced. Inside it has a carbon track eventually the carbon on the track wears off from usage. You can measure it's resistance from end to end, should see abt 350,000 ohms (350K). Then using an analog meter (easier to watch the needle than the numbers jump around on a digital) connected to one end and the center connection. What you should see is a smooth transition from 0 ohms to 350K. If the readings are jumping around it indicates that it's carbon trace is worn/broken. Your particular control has 4 connections. The one that is off to the side is a tap used for tone compensation. This makes it a little more difficult/expensive to find a replacement. You can do the same tests on the tone control just it's 100,000 ohms or 100K.

GL