oof. sorry about your luck, mike. the most thorough way i can think of to tackle this
would be to remove all IC's from sockets, and read voltages on all sockets to make sure
you are getting proper power to them. then, start adding IC's and measuring pins. this is
obviously a very labor intensive approach. best of luck....
--- On Fri, 1/16/09, mborish_2000 <mborish_2000@...> wrote:
From: mborish_2000 <mborish_2000@...>
Subject: [yamahacs80] RE: Replacing all CMOS 4000 Series Logic IC's
To: yamahacs80@yahoogroups.com
Date: Friday, January 16, 2009, 7:40 PM
So, I just finished replacing almost all of the 4000 series logic IC's in my Yamaha CS-80. I
totally screwed it up. I've got sustaining voices, unusual behavior and a couple of voices
that only track the keyboard if you play a few notes at the same time.
In retrospect, replacing most of the IC's might have been a bad idea. One theory that I
have is that the 4006 registry shifters that I couldn't replace are having problems keeping
up with the propagation delay of the new IC's? Furthermore, soldering a cap across the
rails on the TKC board might have been a bad idea too. Electrically, it doesn't make any
sense to couple two rails together but a respectable website suggested it and other people
said that it didn't cause any adverse affects?
Is there any systematic proceedure for restoring these things? Initially, I was hesitant to
turn any of the potentionometers - I figured that the thing would probably get back into
calibration once I replaced the faulty IC's. I was scared of stressing the potentionometers
too. Maybe I should have calibrated it after I recaped and before I installed all of the new
IC's. Some of the calibration proceedures were off by significant values - another reason I
figured that my problem was rooted within the IC's.
Here's a brief synopsis of the problems I'm facing:
1.) Before I replaced the IC's square wave output was distorted if more than one voice was
sounding. This was basically the main reason I replaced most of the IC's. I still have this
problem.
2.) One voice, the last voice played, sustains indefinately in sustain I and II.
3.) Aftertouch doesn't work on the voice that is sustaining.
This thing is really sick and hard to isolate problems. I don't have it in front of me either
so it's harder to blog about it.
Does anybody have any suggestions or referrals?
-Mike
312-363-7286
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