Archive of the former Yahoo!Groups mailing list: Yamaha CS80

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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