Left channel out

probably I would say no. Unless you know how to read a schematic or know how to do certain small static checks on the output devices and the drivers as well as the power suppy feeding these devices.

Does it have any mechanical pots? balance pots? check all the mechanical stuff first maybe the balance pot has a bad connection or somthing. Any slider controls? check them also

There are NO mechanical pots on the system. The "pots" for volume are a special bitsequence comparator, and the signal for the gain on the amp is a modulated matrix signal.

The most common problem for this kind of amps are the safety-thermal switch... They are normally located really close to the output for the speakers. Normally gray or black boxes (30x10x40mm). Flick your finger on them with volume at 9 o'clock...

If you can hear a click, and the sound appear again you've found the sollution.

NOTE! Hazardous currents are present inside the cabinet, mind your fingers, arms and other bodyparts.