Hello Mike, I have a CS-80 that repaired long, long time ago,
more than 20 years....
I have the tech manual, but it is very far from me, now. to see
it and go to the point. But I remember one thing that you can use.
You are trying to calibrate a board that you have changed
components, right?. So look for a pattern that repeats on boards
that do not have suffered a modification and is ok. I suppose that
having 16 OSCILLATORS, you could find some that are OK. I remember
that some parameters are affected by the way you touch the
keyboard.... so I build a simulator of the mechanism with relays
(for replacing the switches) and 555 to simulate it in a
predictable way.
GOOD LUCK!
Gustavo.
On 2024-11-11 10:20 AM, Scott Rodriguez
via groups.io wrote:
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Mike: For the CS-80, when referencing the
Adjustment
Procedure?document, below is what I have learned about the
typos and inaccuracies on the filter and vca adjustment docs and
how I do it.
VCF - Complete Alignment - Page 11
?Make sure to do the sustain level and attack adjustment
procedures first.
When doing the?adjustment, I use two trimmers at the same time
and adjust the peak and gain pots simultaneously. Makes setting
the?High Pass filter quick and easy.
If you can't achieve the correct voltage settings
(sometimes you can ALMOST get there, argh) then you have a bad
chip. Good chips will easily hit the intended target level
every time.
Item 1. The CP3 terminal reference is
incorrect?and should be CP2. I use CP7 however which is
electrically the same thing; it's just easier to get at the
way I do it.
The 4.3 Vp-p value is incorrect and is the zero-to-peak
value. The correct value is double that and should be 8.6
V peak-to-peak to match the pictorial representation.
Item 2.??The terminal reference of CP3 is
incorrect and should be CP8. The 2.2 Vp-p value in the
pictorial is correct.
VCA - Page 15
Make sure you have a good ground reference for the
scope on the card itself. If using a rack mounting
ear, make sure the screw is good and tight (which
should be done anyway).
Item 2. VCA #2 Gain - As shown, but set both
the BRILLIANCE and RESONANCE paddles on the main panel
to the full forward (the low) position to achieve the
correct wave shape.
Item 4. Output Terminal - Rather than using a
scope for adjusting the output VCA to 80,mVp-p,?use a
good DMM and set it to dBm. Adjust the trimmer to a
28.3 mV RMS value. Much easier to do and more
consistent between voices.
Also, lately I've been replacing the voice card
2SC458 output transistor with KSC1815 parts as I've
seen several go bad. Drop-in replacement with a lower
noise figure. Yamaha went to the 1815's for the CS-70M
cards, fwiw.?
Scott Rodriguez
11/11/24
On Sun, Nov 10, 2024 at
11:40?PM mborish_2000 via <mborish_2000=
[email protected]>
wrote:
I'm asking this question basically to see how people have
approached the filter and VCA tuning discrepancies in the
service manual.? I've read several different opinions on
them, but have yet to find a consensus or a correct answer.?
I've got two CS-80s here right now to experiment on.? One of
them I probably calibrated somewhat wrong over a decade ago
and could probably use a new calibration.??
?
Here's the latest take:
?
?
Thoughts?
?
-Mike Borish
