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

[Bob Weigel]

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

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