I was listening to my Yamaha T-80 and suddenly there was no sound. At first I thought the station had gone out but realized I had nothing on any station. I turned it off and back on and it worked for a day. Then it went out again. This time I only revived it for a few hours and then I could no longer revive it. In hind sight it had been dropping out for a second or so every few days but I kept thinking it was the station. The symptoms are no sound and nothing on the signal strength meter. Everything else works perfectly. The station displays normally, the buttons all light, I can change frequency. Even the test tone works. Just no sound and no signal. AM or FM. Any ideas?