How can I fix my ford 6000 radio?

My Ford 6000 cd / radio has stopped working, well the cd player and AM radio works but the FM doesn't. When you scan through the channels it stops on the frequency and displays the correct radio station as though it is receiving a signal but no sound is outputted. Same in another car, all connections seem ok.

It is the 6000 cd player with the knob for the on/off and volume, not buttons.

Please help