Rhodes Chroma Polaris

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