Radio Problems ????

My factory radio in my 1991 LX 5.0 convertible stopped working. When it first happened, it would go off and on for about 2 days. It would be working fine, then shut off for no reason, then come back on hours later. Now it does not come on at all. The radio dial lights up and I can hear the tape turning, if I put in a cassette, but no sound!!

I took the radio out and put another factory radio in, still no sound!! I have checked all the fuses in the fuse block and all are working. I removed each speaker one by one, hopeing that if one speaker was bad the other ones would kick on after disconnecting bad speaker. No such luck!! There is no amplifier under the front passenger seat. Its the factory a/m, f/m casette player from Ford.

Anybody know what the problem could be and what I should check next?


Thanks

Larry