Moog Sonic 6 keyboard failure

Hello,

I bought a Moog Sonic 6 a few years ago that was in pretty rough shape, it didn’t have any of the original knobs or slider caps, but I have since found suitable replacements.

I got a service manual and user manual and got it working pretty well,
however, the keyboard tracking / pitch /tuning has always been dubious at best.

At this point the keyboard has failed completely, it triggers the loudness contour, but does not track any pitch regardless of what key I press.

I’ve spent countless hours trying to get the keyboard working again, but no luck.

Someone suggested that the “Keyboard Bus” is a common failure in this relic, has anyone here had any experience at resolving this issue?

Any help, advice or insight would be greatly appreciated.

Thanks,
Phruknobulator
Canada