Korg Mono/Poly

I have a mono/poly which appeared to work fine for some while. then, 
one day, it stopped working out of nowhere. The gate light still 
lights up when the unit is on and some white noise can be heard when 
keys are pressed, and the filters can be heard to work. Does anybody 
have any idea what might be wrong? I have some basic electronic skills 
and I am competent with a soldering iron. If anybody has any clue what 
I can do, please reply or contact my personal e-mail. 
Thanks a lot,
Bryan