1 bit of ASM advice needed...

Tony Clark clark at andrews.edu
Thu Feb 26 23:23:37 CET 1998


> I'll have to check what type of solder I use - I'm sure it's Kester of
> some kind, and I think that it's the "water clean-up" type. It's
> whatever we used at my old company on the production lines. I'll have to
> get back to you on this one (I'm at work, solder's at home). But the
> problem is real - no cleaning, no work, clean, it works.

   Ah!  This is why then!  Water clean-up types typically use 
"organic"-based fluxes.  These are conductive fluxes that cause all sorts 
of problems when left on!
   Let me tell you a little story about something that happened to us 
here at work...one day a bunch of our circuit boards started to behave 
really strangely...they were drawing more current than normal and the 
output was behaving erratically.  As typical all of the boards were 
checked for various flaws but nothing was discovered until it was noticed 
that the flux residue was different on these bad boards than normal.
   So the boards were washed, and bingo!  They worked.  All of these bad 
boards had a clearish pasty flux residue on them that was different from 
the typical amber colored brittle flux residue left by rosin core.  So we 
ended up testing all of our solder stock looking for culprits.  And we 
found a few.
   Evidently Kester botched up and mis-labled some organic fluxed 
solder!  Needless to say we weren't very happy.  But at least we were 
able to get our boards working.
   Another note, the organic flux had a sort of fishy odor to it when 
used.

> The problems are erratic, but seem to affect VCO's the most (like they
> don't have the right range and don't have the proper scale factor). The
> multimode VCF in the ASM-1 gets all kinds of multi-volt offsets and
> locks up at the supply voltage when the frequency CV is too negative or
> positive. Like I said, only a throrough cleaning makes things work
> right.

   Yep, this was pretty much what was happening to our boards which were 
nothing more than high gain amps for strain gages.
   What I've found to be rather rediculous is that even fluxes labled 
"no-clean" tend to cause these kinds of problems as well!  How can you 
call it no-clean if _really_ you have to clean it off to make sure things 
work right?!
   Anyhoo, perhaps what we need is a good list of different kinds of 
solders and what people's general experiences are with them.  Let us know 
what kind of solder you were using Gene!

   Tony

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I can't drive (my Moog) 55!        |     The E-Music DIY Archive
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Tony Clark -- clark at andrews.edu    | aupe.phys.andrews.edu/diy_archive
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