Vintage Synth Repair

Hi,
  I have a Peavey DPM2 based synth module (it's actually their MidiBase 
module). This module shows occasional DSP #1 power up errors and when 
it does initialize all functions work except there isn't any audio 
output. The digital input to the DAC appears to be missing (clock is 
there). The audio section produces a slight hiss if the volume is 
turned up and down and appears normal. 
  Does anyone have any info on this module? All the chips are in 
sockets. I have a PDF schematic from Peavey Au but without a block 
diagram (Argghhh!). Is there a test program in this box? The reset 
function works, midi in shows notes playing on the screen, sysex works 
fine, and all the controls on the front panel appear to work fine. 
  There are 2 Motorola DSP560001FE20 IC's in this module in a some very 
neat AMP sockets. Switching the DSP's with each other doesn't change 
the symptoms. Email me offline if you can help so far Peavey US hasn't 
been much help... Thank you, Narfman96 at Yahoo dot Com.