[sdiy] A flux 'trace' conductivity that changes drastically with...location??

[Paul Perry]

Sure it is humidity.
Montana is dry as, compared.
Same reason (in reverse) why static electricity is
no trouble up in Oregon. Or here in Melbourne
Australia.

paul perry Melb Australia

----- Original Message ----- 
From: "Bob Weigel" To: "synthdiy" <synth-diy at dropmix.xs4all.nl>
Sent: Monday, September 20, 2010 5:53 PM
Subject: [sdiy] A flux 'trace' conductivity that changes drastically 
with...location??


> Ok... from the 'tales of the repair crypt'..... I'm selling a polysix to
> this guy in Portland.  It works great here in MT after initially
> straightening out some issue on the cpu board as usual from battery leak
> and somehow there was some corrosion that affected joints/traces on the
> front of the analog board..the very front couple there which as it turns
> out I find are to sample/holds for the last channel's vco CV's.
>
> So anyway I wired over those and a little flux there that I didn't get
> cleaned up well and forgot about in the process.  But the thing is..it
> all worked after swapping channel 6's transistor pair.  6 was unstable
> before that.  Now it seemed all fine and I took it to Oregon with me to
> sell to Cole.
>
> Ok it worked when I first got there is the oddity.  Then...it degraded
> by the time I was actually going to deliver it to where it was acting
> insane.  There was interaction in 4, 5 and 6 VCO's.  Hit a high note on
> 4 and then the low notes are shifted on 5.  Hit one on 5 it affects 4
> and 6.  HIt 6 it affects 5 .... Then I noticed as some might recall the
> power supply voltage was 6.5V instead of 5V.  I shut it down and took it
> home.
>
> Got here..it all was fine.  After much effort I finally got the power
> supply to start cracking a bit...I'd located some issue but in
> attempting to find it the whole -15V took a dive for no apparent reason
> and I replaced the regulator and checked ever part...nada.  Couldn't get
> it back in time so I desperately threw another power supply in from a
> unit I'm restoring and headed to Oregon where I had to see my step dad
> before he passed away a few days ago.
>
> Ok... so I'd checked it all in MT again and there was no issue with the
> pitch interaction.  BUT..as soon as I got to Oregon..it's back. It was
> then I finally sorted through the bad diagrams of the analog board and
> found out that it's the sample/hold lines for control voltage for the
> pitch so.... I tried replacing hte 4051 mux to no avail then found that
> it was the flux.  Cleaned it up. All good.
>
> Now...WHY ..why why WHY would it only do it in Oregon?  I mean there was
> zero problem in Montana.  I tried so many times to make anything foul up
> there and finally the power supply did but that proved to be a totally
> unrelated problem.   altitude?  humidity?  lol.  I'm trying to imagine
> how those factors would affect flux that has some stuff in it that is
> allowing a little conduction. -Bob
>
> -- 
> Check out sounddoctorin.com for songs, a studio tour, help
> repairing old synthesizers and parts or thought provoking
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>
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