I looked up that model, and found out it's a Phono/Radio all-in-one that were popular in the '60s & '70s. If the radio also has only one channel of audio, the problem is probably in the amplifier 'innards' and may not be worth the money to have it repaired. If you're at all handy, you might open it up and look for any obvious problems like broken wires. Follow the wires from the output jacks and look for anything disconnected.