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?
>