First you have to find the problem, it could be the control itself is not connected well any more, if you are not comfortable with looking inside the radio, may be someone local might be able to help you out. The squelch circuit is part of the AGC (automatic gain control) circuit in most radios, in order to find anything you would need to open the case up and look where the squelch control (knob) is connected to the circuit board, but before you do that take the squelch knob off and wiggle the control shaft with the radio on and see if there is a different sound as you wiggle the shaft wiggle gently.