Yamaha CS80

Thank you very much David for your input
Not being a tech like some of you,  (i studied electronics for one year long time ago) i get lost sometimes but I understand some of the issues you're discussing and it's always intersting
 
François
--- En date de : Mar, 22.2.11, David Rogoff <david@...> a écrit :


De : David Rogoff <david@...>
Objet : [yamahacs80] various repair topics
À : "yamahacs80@yahoogroups.com" <yamahacs80@yahoogroups.com>
Date: mardi 22 février 2011 13 h 48


  



Hi all.

I spent a lot of the long weekend buried in CS80 guts and thought I'd 
share some of what I found.

First, on the topic of dying chips, I had to replace an IG00052 filer EG 
chip yesterday. It wasn't totally dead, but the output wave shape was 
very strange and inconsistent.

Next, for tuning, there's a really nice way that doesn't require holding 
any keys and/or figuring out which card is active. I just grab the sine 
wave output right off the M cards (pad CP1 - 
http://dl.dropbox.com/u/9224623/trigger%20wiring.JPG). The way the KAS 
works, if you just play one key, all 8 voices go to that note. So, just 
hit A1/A4 as desired and all the voice cards have nice, clean sine waves 
coming right off the VCO without holding any keys. I think the easiest 
way to tune is to run these, one at a time, into one input of an 
oscilloscope and run a reference sine wave (I use ClearTune on my 
iPhone, which lets me easily change octaves) into the other input and 
then set the 'scope to X-Y mode. It's a piece of cake to see the beat 
frequency and get it perfect. A strobe tuner would work great also - 
I've got Peterson iStrobeSoft on my iPhone too.

For calibrating the EG times, I soldered wire loops onto each M card on 
the TRG input (removing the trigger wire temporarily) and the EG output 
testpoints. I then connected a wire to the square wave output of the 
Sub Osc and connected it to the trigger inputs of all 16 voice cards and 
the trigger input of my 'scope:

http://dl.dropbox.com/u/9224623/trigger%20wiring.JPG

Now I can go through the calibration procedures ( 
http://therogoffs.com/cs80/CS80%20Adjustment%20Procedures%20and%20updates.PDF 
). It's still very slow going. I got the first card all calibrated and 
then displayed its output on the 'scope along with each of the other 15 
cards one at a time to get them all to match. This is much easier and 
faster then trying to calibrate them each individually and consistency 
from voice to voice is the most important thing anyway.

Back to my digital day-job now!

David









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