Kawai R50 no sound from Right output

[digix]

Hi All -

I'm fixing up a Kawai R50 drum machine and before I can start bending, this one has no sound from the right output (headphones or line out - the L/Mono works fine).  I've replaced the op amp at the end of the signal chain but saw no difference.  Does anyone have access to Kawai R50 technical information?  I've found schematics for the R100 bu no R50.  Thanks!

[Circuitbenders]

I'd be looking at the volume slider, and then printing out the words "always suspect hardware fuckups first" onto a piece of paper to get framed above your workbench.
I'm saying this as someone who recently spent 5 hours searching for ever more esoteric reasons for a fault in a digital multitrack, before discovering a very obvious crack in the circuitboard!