Discussion about the Korg PolySix synthesizer

Hi,

Probably some issues in the anti-log circuit. To verify note the voltages at
IC31 pin 3. Try a C in each octave. This voltage should ramp up in a linear
fashion as the frequency increases. If not try replacing IC30 (you have
replaced IC31 already, right?). Also take a look at IC19. The A side of it
is a precise voltage reference (output should be 9V). If this is wrong you
might be in trouble. Also make sure that if you replaced Q12 that the new
device is a matched pair and thermally bonded. Two BC549s glued together
just won¹t cut it, but you probably know that!

Cheers,
Andy


On 30/04/2012 18:36, "klosmon" <klosmon@sbcglobal.net> wrote:

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> Hello-
> I'm working on an older version voice board (with the 396 add-on board)
> that won't tune.
> The six oscillators can be tuned to match at the low points & high
> points, but there's no way to tune them to play anything like a
> half-tone scale.
> 
> I've tried the usual (replace the optoisolator, replace the 4051,
> replace the dual transistor, replace the TL071 opamp), but nothing helps.
> 
> Any ideas where else I should be looking?
> 
> Thanks.
> 
> ~G
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