Re: [amsat-bb] Opps! D/C water ingress

["Bryant Winchell" <bryantcw@xxxxxxxx>]

You might also ask your druggist.  He/she might be able to special order for
you.

73

Bryant, W2RGG/6
----- Original Message -----
From: "Louis A. Mamakos" <louie@TransSys.COM>
To: "Franklin Antonio" <antonio@qualcomm.com>
Cc: "John Wilcox" <ns1z@arrl.net>; <amsat-bb@AMSAT.Org>
Sent: Sunday, August 05, 2001 7:20 PM
Subject: Re: [amsat-bb] Opps! D/C water ingress


>
> FYI, I had once gone on a hunt to find fairly pure isopropyl alcohol; the
> stuff you can commonly buy at the grocery store is around 90% pure, with
> water and who knows what else making up the rest.  My original need to was
> clean some optics (telescope objectives, and removing people-grease from
> eyepieces).  I finally found 99% pure anhydrous alcohol at
> www.mcmelectronics.com for a fairly reasonable price.  They sell it for
> electronic service applications.  I think a 12oz can was $7 or so.
>
> louie
> wa3ymh
>
>
> > At 10:36 AM 8/5/2001, John Wilcox wrote:
> > >It now appears that water has entered into my CalAmp downconverter and
is
> > >causing the problem. I have dabbed it out as much as I could but it
does not
> > >appear to be enough to restore its original outstanding performance.
> >
> > I don't have experience with CalAmp downconverters, but I have had
> > experience with cell phones that have fallen into water.  One thing I've
> > learned is that it takes a lot longer for these things to dry out than
you
> > would imagine.  Even if it looks dry, water has made its way into places
> > you can't see.  I've had the experience of opening up a  cell phone,
then
> > letting it dry out in a slightly warm (150 degree) oven for 2 or 3 hours
> > after which it didn't work, then found that it worked fine after being
left
> > in the oven for 24 hours.  (Turn the oven off before putting the
electronic
> > gizmo in there.  Just let the residual heat of the oven help the
> > drying.)  I think it just takes a long time for things to really dry.
> >
> > >  There also appears to be some sort of residue left from this attack..
> >
> > I used to work on electronics that was installed outdoors.  I saw lots
of
> > cases of water ingress in electronics that was powered up during the
> > ingress.  The combination of water and DC voltage is evil.  Water,
unless
> > it is distilled water, conducts electricity, and electrochemical things
> > start happening.  These electrochemical reactions involve the tin and
lead
> > in the solder, and the copper in the circuit board traces.  You get
various
> > conductive salts.  (I'm not a chemist, so don't yell if I didn't get the
> > terminology quite right.)  This allows the water to conduct more
> > electricity, and so forth.  This will eat away traces if you let it go
too
> > long!  Meanwhile, it is as if someone has added some resistors to your
circuit.
> >
> > On the other hand, if the board was conformal coated, and water never
got
> > across live conductors, the residue might just be the normal residue one
> > expects when dirty water evaporates.
> >
> > I suggest you get a toothbrush and some alcohol (and maybe some water if
> > that works better) and try to remove the residue from the circuit board
as
> > much as possible.  Especially where traces run close to one another.
> >
> > >I have heard of folks putting electronic equipment into the dishwasher
and
> >
> > I would recommend against that.  Could destroy some components.
> >
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org