Vintage Synth Repair

At 16:07 Uhr -0400 08.05.2008, Roy J. Tellason wrote:
> I *strongly* disagree with a few statements that he makes there, one of them
> being how tantalum capacitors degrade with age -- that's not the problem in
> the Omni, running them too darn close to their rated voltage is, and
> replacing them with 35V units (where the originals were 25V) takes care of
> that. I also strongly disagree with his assertion that 4000-series CMOS
> parts degrade with age -- there's no basis for that at all, as far as I can
> see. He also doesn't impress me as being much of a technician if he smoked
> the power supply somehow (twice!) while troubleshooting some other problem...

Given the number of smoked tantalum caps I've seen in various synths I'm
simply not sure if the caps produced about 30 years ago might not have a
more generic problem.

The german wikipedia states that older tantalum caps are sensitive to
low-ohm switching and could easily fail under such circumstances. Don't
know if this could be a reason.

As far as the 4000 series CMOS goes: I've already quoted another URL (also
found on Peter's site) with a description that I found pretty convincing:

http://www.oldcrows.net/~oldcrow/synth/tips.txt


In the last Omni I'm currently fixing about 5 of the 4000 series chips were
partly dead. Replacing them took care of all "dead" voices at once.

-- 
Malte Rogacki gacki@...
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"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
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