Yamaha CS80

I'd love to hear your opinion on this - in general ofcourse, I'm not necessarily looking for direct solutions, just about your general feeling on how to proceed from here.

Thanks in advance!
Rainer

--- In yamahacs80@yahoogroups.com, "Rainer" <rainer.keizer@...> wrote:
>
> Hey people!
> 
> I've had my CS 60 serviced a while ago, turning it into an enjoyable,
> playable musical instrument again, but there are still some issues which
> I'd love to see resolved. Because the servicing was rather costly and
> I'm not too eager to jump right in again, I'd love to hear your opinion
> about what could be causing the problems. I've tried to describe them as
> accurately as possible.
> 
> Voice 2
> 
>     * The VCA is very loud; even if VCF Level is completely turned down
> it gives a loud hiss.
>     * The tone fades away quite quickly in a distorted way, instead of
> staying in the sustain phase when holding the key.
>     * VCA attack is not right, when VCA attack is set to max and VCA
> sustain to zero the sound fades in, then peaks with almost a 'pop' when
> going to the sustain phase. Also, the attack takes longer than on other
> voices.
>     * MUCH more hiss than other voices
>     * When the ring modulator is fully on (attack and decay set to 0, and
> speed, depth and modulation set to full) a high sound is heard shortly
> when striking a note, and that sound is heard again when releaseing the
> key, but then it is pitching down like a very fast pitchbend of about
> two semitones.
> 
> Voice 3
> 
>     * VCA release: when VCA release is set to 0, VCA doesn't go into
> release immediately after letting the key go, or at least it 'hangs on'
> a little bit longer.
>     * The likely cause for this seems to be the VCA decay, because when
> that is set to 0, the release isn't much different from other voices -
> so it might be that it is actually the decay phase that 'hangs on' too
> long.
>     * VCA decay is at least five times as long as on all other voices
> when VCA decay is set to half.
>     * More hiss than other voices
> During the servicing, the following things have been done:
> 
> Modifications:
> 1) 4 voices did not have TempCo diodes --> add them and replace other 4
> to have all 8 voices matched TempCo diodes.
> 2) Inside, a board with 8 LED's is add to easily see which voice(s)
> is/are active. This for the easy of adjusting the parameters of each
> voice. - Inside a special trimming tool is mounted in the center of the
> top.
> 
> Service:
> 1) Recap all boards (electrolytic caps and partly ceramic) 190x.
> 2) Replace the S&H caps with high Q ones (8x).
> 3) Replace all tuning pots with 20 turn cermet ones (32x).
> 4) Check & Readjust all parameters (203x).
> 5) Check & Treat all pots & switches.
> 
> Only one CD4016 was replaced on the ringmodulator; I don't think any
> others were replaced.
> 
> I wonder if replacing the VCA chip on voice board 2 and 3 would do the
> trick? The capacitors *should* have been replaced, but there's probably
> more than 190 in a CS to begin with? :-) so perhaps some on the VCA side
> might not have been replaced? And where do I get replacement VCA chips
> or preferably some rebuilt modern equivalent?
> Also, after reading some of the stuff people like Old Crow do on CS's,
> I'm wondering if my tech did enough for getting everything right again -
> like replacing lots of 4xxx chips, and adding decoupling as is described
> by Old Crow. Is that really necessary?
> 
> Thanks in advance for your added expertise!
> Rainer
> 
> 
> 
> 
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>