1 bit of ASM advice needed...

[Stopp,Gene]

One thing that always seems to plague me, even when I plan for it, is
the disturbance caused by solder flux.

I built another ASM a couple months ago, and cleaned it with de-fluxer.
When I fired it up, the VCO's had the wrong frequency range, they didn't
track at 1v/oct, the VCF locked up outside of a narrow frequency range,
the LFO was asymmetric, all kinds annoying stuff. I actually changed out
some parts before I tried another (serious) session of de-fluxing, and
that fixed it all up. The sad part is that I have a good scope! I should
have known better.

I don't remember having this much trouble in the old days.... perhaps
modern solder flux is of a different composition than the old stuff
(environmental considerations, etc.?).

Anyway, try a good cleaning, and then clean it again after you think
it's already clean. And, of course, make sure the components are the
proper values.

 - Gene

 ----------
From: Andrew Schrock
To: synth-diy at mailhost.bpa.nl
Subject: 1 bit of ASM advice needed...
Date: Thursday, February 26, 1998 3:52AM

Ok, I promised myself I wouldn't go to sleep until i troubleshot and got
my last (out of 3) ASM-1 VCO to oscillate.

I finally did it, but with 1 problem: it doesn't respond to negative
input
voltages... thus tuning it is a bit hard since it's so unbearably high
pitched. It's not a physical problem with the tuning trimpot, I can see
that it just doesn't _respond_ to any voltages below 0. PW, FM, and CV
in
all work fine, just with a terribly high-pitched tone.

This sounds like an easy fix somehow, but I'm pretty tired... if
somebody
could privately email me a hint it would be much appreciated.

Update: My semi-modular handheld filterbank is 1/2 built: envelope
follower, LFO, and Attack/Decay envelope generator are all online, now
only the VCF needs some troubleshooting time...

Andrew
(whose time seems to get sucked up by a strange force as soon as he
picks
up the soldering iron...)