Radio power switch issue
 

My 79 ZX still has the original Hitachi radio and it sounds okay since I upgraded the speakers a few years ago. But it has an issue with the volume switch; the volume will unexpectedly drop down to only 5% of normal and it will lose the FM stereo signal (the stereo signal light goes off and it sounds mono too). I have to turn the radio off and on to restore it, but that doesn't always work and is getting more and more frequent.

Has anybody ever fixed a similar problem? I don't know much about electronics, I wish I could fix this myself but who knows. I guess my best bet is to pull the radio and try to find somebody who understands what to do to get the contacts to do what they should be doing. If anybody has a suggestion for somebody to send it to who could figure it out and fix it, I would appreciate it.