Korg Poly800/EX800 Users

Hi:
 I'm new to this list but I have a modded poly800 (did the cutoff/rez 
knobs and a noise too) I used a 100k pot for the filter cutoff, a 50k 
for the rez, and a 250k for the noise all audio and they work great, 
I also added a momentary switch to the pedal so I can advance the 
programs by just pushing one button intead of having to do all the 
buttons presses to get a patch or having yet another pedal on the 
floor. 
 But alas, it has stopped working, I can only seem to be getting 
noise and resonance, so I suspect the DCO's are gone. Can anybody 
point me in what direction I should go, I did reload the memory tape 
and all the time I'm getting a "GOOD" message, and the patches seems 
to be different with the  different banks I'm loading (I have the 
original tape plus some by Kid Nepro). This particular unit has a 
battery for memory back up and it has good charge (3.1 v)
 Thanks
 Jorge