sony xr-c9100 signal problem
 

My sony xr-c9100 head unit won't play tapes or amplify the signal from the unilink cd changer, but the radio is fine. Everything is perfectly normal, the tape and the cd changer are fully contolled and if you look and listen to the head unit and changer everything is working fine, but I get no sound when I select the tape or cd, but with the radio everything sound fine, any suggestions, thanks