[sdiy] keyboard controller leak

[Gene Stopp]

Possible cause: solder flux causing sample/hold leakage. Solution: clean the
circuit with isopropyl, 91% or higher, 100% preferred. Once dry, clean
again, repeat a couple times. Warning: test any exotic capacitors for
tolerance to isopropyl first, since some of them can melt in alcohol.

- Gene


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Pat Kammerer
Sent: Wednesday, January 11, 2006 5:44 PM
To: sdiy
Subject: [sdiy] keyboard controller leak


I finally got back to testing and mounting a DIY version of Ray Wilson's
single bus keyboard, and I think I have a problem, but maybe not.  The issue
is that the output CV starts about right, but then drifts upward eternally
starting at about 3 seconds, maybe less.  Thus if I'm controlling a VCO and
just taking the ouput of that, the frequency starts in tune, and then raises
in pitch slowly until it is inaudible.  It take a minute or two.

I'm assuming this has to do with a S&H capacitor or something, but I could
be wrong.  I've been over the board checking connections and placement
several times.  I fixed any other issues I had with the board since I built
it, so this is what's left to track down.

Any help would be appreciated.