How can I fix my Sherwood RV-6070R/RVAudio/video receiver?

I have a Sherwood RV-6070R/RV Audio/video receiver. Listening to FM radio it cut off the sound suddenly. When switched off and on again it worked for about 15 secs and then cut off again. it did this again and then wouldn't work at all. There was power getting to it. Any advice?