Sometimes problems with intermittent channel operation, including a channel being always out are caused by dirt in the controls. Try vigorously operating all of the controls a number of times. If the unit is turned on at low volume, you can listen for any sound or noise coming form the derelict channel. Also, try reversing the speaker hook-up. If the problem follows the speaker, it is not the unit. Are the speakers plug in wires, or bare. If plugin, its possible there is a break in the wire you cannot see. Gently wiggling the connection and the wire at the plug will sometimes identify a break.
