Vintage Synth Repair

On Tuesday 15 July 2008 16:20, thainmlh wrote:
> Hi, new to the list. I have two questions pertaining to an ARP Axxe
>
> 1) It seems to me that the CV Memory needs alignment or repair. If a
> note is depressed and released, the pitch slowly climbs. If the key is
> depressed and held, the pitch remains constant.

I've hit that one before,  but can't recall just what it was.  Bad op amp 
someplace?  Trace your CV through the circuit,  back,  until you find 
something funny.

> 2) When a key is released, occasionally the note will release and
> sound again. I've yet to look at how the keyboard functions, the
> schematics show a switch, but I am not sure how the switching was
> implemented.

The ARP keyboards used two contacts (some of the early stuff used three),  one 
to determine the CV and the other to generate gate and trigger signals.  Look 
at the relative timing of these when you press a key -- which one makes 
contact first?  Scope your gate and trigger signals,  if you have a scope.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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