[sdiy] Name that PolySix mod

[Bob Weigel]

Man...I'd love to go back to doing games of name that synth sound 
byte....but everything has been hard of late.  The last several machines 
I got to fix up plus some I already had have been slow going.  But I got 
a polysix the other day which..mostly works but the oscillators are just 
making noise instead of tones right now... but the thing has an 
interesting mod.  I thought I'd see if anyone can imagine what it might 
be for.

1) 7 toggle switches they located under the wheels. 
2) wires from them to a little board under the keys near the 8049 chip 
(processor that does key scanning and outputs the CV data to the DAC 
which..btw is jittering at the moment but responding to key movements. A 
fairly significant bit seems to be undercertain about where it wants to 
remain...
3)  On that board they shaved the face off the two 16 pin chips I think 
they are and there's a trim pot and an AM9716DC  chip which I think is 
an EPROM?.  And a couple resistors in series with the trim.  That's it. 

Hmm...Oh the connections go to the data line buffers that go to the DAC 
resistors.  Could account for the jitter...I know.  I see no variation 
in the DAC output when I move the switches.  But wonder ....was it some 
kind of funky CV scrambler?    Or am I missing something else they could 
have been doing there?  Maybe it's like Spinal Tap..."One of those 
mysteries...best left unsolved.." :-) -Bob