My first suspicion would be an output relay or dirty pod/s but it could be any faulty component. Unless you can fix it yourself it's really not worth repairing it. Paying someone would cost more than what those are selling for. $100-$200.
kenwood kr 4400
I have a kenwood kr 4400 stereo receiver that has an unusual problem. when playing an aux input (or any input) the left channel is dead with the stereo button engaged. when I select it in mono both channels play fine and has stereo separation between the two speakers. Does anyone have any ideas or suggestions. It is a beautiful unit that I would like to get operating correctly.