no fuse, but there is a few things that could be wrong. it could be all the right side speakers (not likely), the preamp section of the radio (or amp) is only left and right (2 channels). this section of the radio/amp is more than likely the culprit. I am assuming your problem is with all sources (AM/FM/Cassette). unfortunately there isnt an easy way to find out the culprit. a good repair shop or if you have a buddy that also owns a 325 that you can borrow his radio

. really after 13 years of service, the radio is past its time to let go. a new radio would be better than repairing yours, you will get more features, i am assuming a CD player, more power, and better sound.
hope that helps...