Vintage Synth Repair

<< Hi folks, before I take this to my analog synth repair guru:
I have a PolySix that won't seem to respond to the tune control or the bend
control.
Does anyone have a suggestion why this may be the case >>

I gave away the schemos when I sold mine, but afaik, the tune & bend controls 
function exactly as per any voltage control synth, while pretty much every 
other control on the poly-6 panel goes through an a>d, then through a d>a. this 
is so it can read the settings into memory, & apply memorised settings onto 
the analogue voice card.

so... the tune & bend voltages are summed somewhere, & mixed with the 
voltages assigned by the keyboard scanner onto each voice. assuming the keyboard 
itself still drives the voices normally, you should trace the circuit from the 
backs of the tune & bend-wheel, probably the middle of each pot, & see if there 
isn't a duff op-amp (buffer) stopping them doing their stuff.
it could even be a connector that's come off. a simple metering of the tune 
control's terminals will tell you if it's actually in circuit. if it is, it 
will be this buffer amp that's failed.

duncan.