Hi vldmrssnsgrbjrn (???)
> I just purchased a mono/poly which is pretty great except that I can't
> seem to assign the poly button, It doesn't light up and I seem to be
> stuck in either unison or unison/share mode. Has anyone had this
> problem or have an idea about the cause?
I don't think that the uP is the cause.
Does selecting the polymode unselect the Unisono or Uni/share mode?
If yes -> only the LED or LED control is broken.
If no:
Can you select the Up/Down Mode for the arpeggiator?
If no -> the adress line might be broken.
If yes -> the switch is not connecting or the cable from KLM-356 to
KLM-353 (switch/LFO/Bender board) is broken (or in both cases a solder
point is dead).
Regarding the LED: Q5 on KLM-356 might be dead.
Good luck!
Florian