Yamaha CS80

Hi Will,

congratulations! I should adjust the Chorus/Tremolo section of mine, too. Any advice how to do it? Any caveats? I wouldn´t want to haul my CS around just for that minor bit of surgery...

Stephen

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  ----- Original Message ----- 
  From: willgregori 
  To: yamahacs80@yahoogroups.com 
  Sent: Saturday, January 24, 2009 5:12 PM
  Subject: [yamahacs80] CS80 1271 back on duty...


  Dear CS-80 friends,

  just want to report that my CS-80 no. 1271 has been successfully 
  resurrected. I bought it 8 years ago from a guy in switzerland who had 
  it sitting around probably more than 20 years without any service in 
  his garage. Shame on me, I found no time earlier to take care of this 
  baby, but now it plays like new again!

  Needless to say, I am pretty impressed by the quality and depth of its 
  sound when fully calibrated to factory specs.

  Since this was my first CS80 to take care of, let me share my 
  experiences when going through the complete tuning procedure:

  1) Some Keys had no velocity: First I suspected some damaged 4000 chips 
  and started swapping these on the TSB boards- until i noticed that the 
  reason was actually some bend metal contacts on the Key sensors, grrr! 
  Re-aligning the contacts helped immediately. 

  2)Following the tuning procedure I stucked quite early because the 
  voltages on the KAS board seemed way off what should be right and could 
  not be adjusted with the VR trimmers to factory spec. It took me quite 
  some time to realize that I was using the wrong ground for this 
  measurement, I took electrical ground straight from the PSU- but when 
  taking the ground directly from KAS board it read out the proper 
  Voltages perfectly. So from then, I always pick up ground from the card 
  I am working on, not the PSU ground.

  3) Pitchbend did not work: Changed CA3140 on BA board

  4) Reference tuning Voltage on KAS board dropped from 4 Volts to 0 
  Volts suddenly: Broken TR29 on BA board.

  5) Reference tuning voltage on KAS board suddenly went to 8 Volts: 
  Broken 4069 clock

  6) enevelopes sounds different for VCA and VCF on each Voice, and some 
  Voices had no attack at all. First I suspected some broken ENV chip 
  here. The complete alignement of the envelopes is a quite elaborate 
  procedure. I had to buy a digital oscilloscope for it and go thru the 
  procedure several times, but finally everything could be adjusted 
  without the need of exchanging ENV chips.

  7) Output level of Voice cards was different for each voice. Adjusting 
  the levels to factory specs (VCA gain should be 80mV) resulted in a 
  very low general output level, so I suspect this value is wrong. I just 
  increased the level up to 200-300mV, just before it starts clipping the 
  chorus and ensemble section. Now the output is much hotter and SN ratio 
  of Effect section much better.

  8) Effect section: The adjustment procedure for the chorus and ensemble 
  section seemed not to work well on my particular unit, so I adjusted 
  this by ear to a minimum of noise and a reasonable effect level, 
  skipping the specified values here.

  9) Tuning of Voice boards: Looking on my Voice boards I found no 
  temperature compensation diode, it is printed on the board but not 
  fitted. But tuning my unit was quite easy finally, after completing the 
  tuning procedure it is in tune immediately when switched on and stays 
  like this pretty well. It seems I have some magic VCOs...

  Now the only issue left is to replace a bulb in on of the program 
  buttons, but this should be not a big problem,

  cheers, Gregor



   

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