Hey Arno,
with my PCM70 it WAS the DAC. And with fault-searching I found out three interesting things: 1) The unit uses one DAC for 3 signals! In, Out L and Out R, this all via multiplexing the DAC (I think it's successive approximation for the input... Well - it's an 80's piece of gear...). 2) It's a 16 bit unit, not as often said a 12 bit and 3) All these dbx VCAs don't make a compander-system but are only for the dry/wet-mix!
O.K. but the effect with the dead DAC was: There was nothing at all coming out when in 100% wet, but everthing nice and clean when in 0%.
So therefore I doubt that "outoftune's" unit lacks a new DAC (which is hard to find and if - expensive...). But I wouldn't swear so.. My first suggest: Re-RAM the unit. It's the least expensive step after recapping, so... But be careful not to order SMD's!
Chris