Behringer PMP6000 - no L channel output

[telecaster]

Looking for schematic help. The problem is in the top board, before it goes down to the power amp. The Phones and Main 1 just have R channel output, no L. However, Mono out, Mon1, Mon2 and Main2 all have L out (and R). I tried using the PMP5000 schematics from electrotanya, but there are too many differences to isolate the problem. If the 5000 and 6000 share common design to generate the Main and Mono out (to jacks and Power amp), it is likely there is a 4580 op amp that may be the failing stage. From looking at the back of the board, maybe IC6? If any of you Behringer schematic holders could help without violating your CDA, I'd appreciate it.

[Enzo]

First, just check the master fader and see if it is open.

[Jazz P Bass]

Behringer PMP6000 Schematic

Here is the schematic.

[telecaster]

Jazz P - thanks for the schematic, it is a great help.

Enzo - your guidance is appreciated, also a great help. I ohmed out the slider and initially thought it was ok - it read 10K and the wiper varied with the position of the knob and matched the other working side. But with a signal applied, nothing gets through to the wiper going to the 5K1 (R368) resistor feeding the op amp input for the "L" channel. Thanks for the tip!

EDITED post: Actually, I just searched Mouser and answered my own question - there is an ALPS pot that is dual 10K Audio taper, Mouser part number 688-RS60112A600N.

Thanks to Enzo and Jazz P Bass for your help!