Vintage Synth Repair

At 16:40 Uhr -0400 08.05.2008, Roy J. Tellason wrote:

>> 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.
>
> How did this manifest itself, and what sorts of things were you observing in
> terms of the chips?

Let's see:

one 4520: did not properly divide down on a single pin (all other pins worked)

one 4069: no output on some pins

three 4025: no output or intermittent output (here all pins of all three
chips were somehow affected while the two chips above worked at least
partly)

I also replaced a LM339 which appeared to be dead, too.


-- 
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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