I have only switched on my hi-fi after 10 years of not using, I would have known what the problem years ago but alas I can't remember.
However tuner tape cd (appear) to be working but not coming through the amplifiers. I went round to the back and found everything pretty tight ie wires etc for the amps
Try turning the volume switch up and down vigorously, I think some kind of film develops in the switch and needs wearing off. Our bedroom radio does it now and again as we dont change the volume too often. Could be that?