Yamaha CS80

My guess would be the saw- and/or pulse-gate is always open. Try 
replacing the FET6 or FET7 (2SK30) or TR6 or TR7 (2SA561). However, 
you say the waveform can be heard even when the vcf-volume is 
closed. Then I would say the sinewave is not a pure sinewave. Does 
the waveshaper output a perfect sine ? You'll need a scope for that 
on pin 2 of ic9. Or does vca3 (IG00151) distort the sine-wave ? Try 
replacing vca3...
Good luck.

--- In yamahacs80@yahoogroups.com, "oberheim64" <tommysalsero@...> 
wrote:
>
> Hi. 
> My name is Tommaso, live in Italy and I had in the last 10 years 
> three CS80! 
> The second was in perfect condition and 
> I sold to a dear friend in Italy. 
> The third I found recently, I could not live without a CS!
> I started with the restoration.
> Now the beast was in perfect condition externally, perfectly tuned 
> but with a  little problem on the five Mboard on Channel One.
> With the Sine wave only (VCF volume closed)
> In addition to sine,I Feel another waveform  similar to sawtooh.
> And the waveform (Saw e Square) of the channel one are closed!
> I Change all the IGO chips in the Board,but without any positive 
> effect.
> Then I changed the polarize electrolytic capacitors.
> 
> Same problem...
> 
> Now,they may be the 1 Uf 50V not polarized capacitors?
> Or the other caps?
> 
> Sorry but I do not have an oscilloscope.
> Some suggestions?
>