Theres a few places around the net that state that DCO1 is in fact a VCO 'by the signal generation method', whatever they mean by that. I haven't checked it out yet but you are right, if they are 100% digital then its unlikely there would be any way to retune the voices as in theory there should be no way they could drift.
I've been through the service manual and adjusted the trimmers on each voice so that the filter, EG and VCA are as identical as i can get them but the tuning remains a problem.
There aren't any electrolytics in the area of the board that seems to control the pitch of each voice so that removes the obvious possibility of failing caps. I guess its time to get out the multimeter and test every voice for differences.
--- In DW8000@yahoogroups.com, "PC" <paul@...> wrote:
>
> My Poly-61M has some serious battery corrosion issues on the main board (KLM-509A) and is currently out of commission until I repair that, but since I've already got it town apart, I can look at the analog board and tell you it's got several trim pots for each voice labeled: VCA ADJ, EG ADJ, FC ADJ, and RES ADJ. Unfortunately these are not responsible for adjusting the pitch.
>
> It also is a good time to point out that the Poly-61 has DCOs, which implies that the tuning is digitally controlled, and probably compensated as well. This was a "feature" after a decade of completely analog synths that wouldn't stay intoned. So overall, I don't think they really intended for the oscillators to be trimmed.
>
> I expect that your tuning problems might originate from some bad components -- resistors and/or capacitors which may have been faulty. It may be possible to inspect them closer to see if they are leaking, and you can use a multimeter to check the resistors while the power is off.
>
> Check out my Poly-61 photos in the Photos section if anyone else wants a closer look! -pc