Yamaha CS80

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> 	Fernando Zarone <mailto:fernandozarone@...>
> May 9, 2011 2:57 AM
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> Hi all,
> after the long trip through overhauling my CS 80, I got to the point 
> of VCF/ VCA calibrations.
> David, I appreciated your idea of connecting wires to the trigger 
> points so much! Now, I am using a square wave from my aux outs of the 
> 921 oscillator (Moog modular 55) and it works fine.
> I am facing the same problem as you did, David: no problem for the 
> short Attack time, but setting the 3V at AF the slope of the scope 
> visualization becomes almost horizontal, so the end point is very 
> tricky to be detented and matching the time measurement to specs is 
> not easy.
> How did you solve the problem? I think that, once having one M-board 
> calibrated, it should be an (annoying) game, superimposing the other 
> boards' waveforms to it. But what for the first board ??? Yamaha 
> suggested to use "one good M-board for comparison", but I found the 
> short calibrations (8V at AF) longer than required (about 25 ms): 
> probably they used to be calibrated by ear, so I guess no one board is 
> reliable as to factory specs.
> I think that the topic is paramount.
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Here's what I did.
1) removed top panel so I could get to back of M-cards without removing 
them from (raised) card cage
2) unsoldered all TRG wires to M cards and soldered in little wire loops 
I could easily attach clip leads to
3) connected all TRG inputs to Sub Osc square wave (tapped off op-amp, 
before resistor attenuator
4) calibrated first (M-11) card with 'scope.  Took many passes back and 
forth between 4ms and 125ms settings.  125ms very hard to see with 
analog 'scope. I used falling edge of Sub Osc as trigger (negative 
voltage = note on)
5) calibrated other M cards by displaying them at same time as M-11 on 
screen and getting waveforms to match.
5b) for channel II boards, used 2nd voltmeter to measure difference in 
attack voltage between Channel I and Channel II and made sure it was 0 
volts by tweaking panel slider.


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