happy holidays tom! so sorry to hear about your situation here, that sucks! ive been there(there being the place you are when replacing parts surfaces a NEW problem), very frustrating, you earned that drink sir.
while i cant help you with your particular issue regarding CMOS id-ing, i did want to weigh in on your other cs-80, and doing this job on it.
i have learned a ton of things off of scotts old crow site, and the pictures alone are worth their weight in gold. it is an amazing resource. im merely weighing in to pass along another side of the coin. when i got my cs-80 this year, i planned on a full restoration. i did the PSU, and calibrated voltages, then tuned. i was planning on doing all the CMOS chips per scotts site, but just to double check, i weighed in at Dave Hecht's tech forum(mostly pro audio, good number of experienced techs in there) on how best to replace all the CMOS chips on all 4 of the boards underneath the manual.
the majority of the responses there urged me to reconsider "shotgunning" parts, and specifically called into question the practice of replacing CMOS chips as preventative maintenance. most tech people there said that it is a bad idea. i had already started the job(was using sockets), but stopped where i was per their suggestions. i have all the chips/sockets to finish the job, but decided to wait until i see a problem to tackle those boards. i did not perform the decoupling caps on the TKS board yet. i am not in any way calling into question the validity of either side of this, as i am ultimately not an experienced enough tech to have fallen on one side or the other yet to know how I feel personally! im merely saying that the jury may not be completely unanimous on the idea of replacing CMOS chips as preventatively sound. however, i doubt that many folks are more experienced than scott and kent on these matters, so i would personally put more stock in their opinions than
most!
merry christmas, and be thankful for your working cs-80!
Quazimodo <
noddyspuncture@...> wrote: Merry Xmas guys,
Here's what I decided to do during my Xmas holidays....
I decided to service and perform some of the mods to one of my CS80's
- namely to replace all Power Supply filter caps, then set the
voltages. Next I wanted to do the decoupling mods to the TKC board as
outlined on Scott's site. Then I wanted to tune her up using a dual
beam scope as has been mentioned here before now.
OK, I did the PSU caps and the voltages set up fine. Next I soldered
very carefully all those .1 caps across all 28 IC's on the TKC board.
I even added the electrolytics (the correct way round on the +8.5 and
-6.5 volt feeds) and I was wrist-strap-earthed throughout. When I
fired her up it all worked fine and I set about tuning her up.
So far so good. The tuning went well and I was really happy with what
I had done - I left this machine on for quite some time and played her
almost all day a couple of days ago. Remember, this was a 100% working
synth before I opened her up...!!!
Today however I turn her on - and I notice that a voice is out on
Channel 1. Hmmm... I check the card and there's no waveforn on the O/P
of the Osc chip. So that's a chip gone down. Next I notice I have no
aftertouch... Hang on, it seems intermittent here and there. It has a
weird pattern .... some notes intermittent, others just don't respond
to after touch and then the lowest octave seems to have a mixture of
notes with NO aftertouch and others with constant MAX aftertouch.
I reckon I've disturbed something somewhere and maybe I shouldn't have
attempted this servicing after all...?
I am concerned as I wanted to perform these exact procedures on my
other 100% working CS80. But I fear I won't have a working one between
them if I do..!
Could any techs here maybe point me in the direction of how to
determine which 40XX IC on the TKC board services which note's
aftertouch on the keyboard? The manual doesn't make that clear at all
(to me anyway)
Cheers for now guys, hope you all have a better one that I'm having.
I think a drink is in order now....;^(
TOM
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