Vintage Synth Repair

Hello all, I'm working on a Moog Source and wondered if anyone here has experience with repairing these?
My Source powers up, all membrane switches register as does the data wheel, all parameter values change as expected but there is no sound. The power supply is fine with all supply voltages present. I have signals on the synth board eg VCOs and LFO but cannot adjust any values - I'm thinking there is a problem on the digital board but my experience with digital electronics is limited... therefore any help or suggestions would be greatly appreciated.
My Source is serial no:1788 and has version 2.2 eprom.
Many thanks in advance, James.

>>I'm thinking there is a problem on the digital board but my experience with digital electronics is limited... <<

james, do you have a schemo? are you able to tell if the d>a converters are functional? does the source have a midi kit installed? does it respond to cv/gate input? can you find a signal at the output of the filter? try turning the resonance right up & see if a signal appears before the primary vca. I will have a look at my own scemos, see if I can think of anything else. one of mine used to do something weird when it had a midijack converter in it- sometimes the pitch would go supersonic. I took the damn thing out & the moog's fine now. :-)

duncan.