I have a Sanyo Plus Series amplifier AM FM receiver that randomly makes a very loud popping sound from the left speaker channel. Even with the volume turned all the way down and no speakers hooked up, I can see it register on the speaker output meter. I've had this amp since 1979 and it has always worked perfect. Is there anyone that knows how I can fix it. I am aware of the fact that it would probably cost less to buy a new one than to pay to have it fixed, but I can't afford either as I'm presently unemployed, that is one reason I would like to fix it, plus I've had it so long and it has always been a good amp.

Any repair advise would be greatly appreciated.

Thanks in advance.