Korg Poly800/EX800 Users

Thanks to the apparently dead search function on this group i'be just trawled through about threee thousand odd posts by hand and still haven't come up with a solution to the problem with my poly800 mk2.

Its been mentioned a few times before but nobody has offered a solution. Basically all the lights come on, i can change and save parameters, all the midi and sysex seems to work fine as i've loaded in the factory soundbank, but all i ever get out of the thing is filtered noise and no DCO tones. The noise source, envelopes, delay and filter are definately working but theres no DCO's.

I've re-written the firmware onto a fresh eprom and even replaced the MSM5232 with one i know is working fine. The +-5V supplies appear to be fine and the NJM2069 is also working properly. There just doesn't seem to be anywaveforms from any of the MSM5232's DCO outputs and nothing at the NJM2069 mixer inputs. 

If i turn the volume right up and play some keys i can hear a tone very very faintly that does change with the envelope settings, but it doesn't track the keyboard with pitch.

Any ideas of what i should be lookling at next would be gratefully received.