I agree about the trimmer. Also I have seen broken jacks which can
mean no output.

Flip side is it could have been a blown DAC (happened to me once)
which is difficult to replace.

Another thing non-techs should investigate when by a polaris is
detuning due to cap drift. I wrote a post about that a while ago.
Basically you want to check to see if any voices are excessively
detuned or have problems tracking pitch due to aged S/H caps.

-Ben