You guys crack me up.

Mike Buetow

--EMS account acquisition: March 28 at www.PCBChat.com
On Mar 26, 2012 1:26 PM, "Inge Hernefjord" <[log in to unmask]> wrote:

> Yeah, this puts the heat on the phones.
>
> On 26 March 2012 18:52, Paul Edwards <[log in to unmask]> wrote:
>
> > Thanks Bob...
> >
> > This puts the meat on the bones...
> >
> > Paul
> >
> > Paul Edwards
> > Process/Quality Engineering
> > Surface Art Engineering
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
> > Sent: Sunday, March 25, 2012 8:57 AM
> > To: [log in to unmask]
> > Subject: [TN] More Information on Casini Tin Whisker Investigation
> >
> > > From: Leidecker, Henning W. (GSFC-5600)
> > > Sent: Friday, March 23, 2012 7:55 PM
> > >
> > > Subject: RE: Any Information on Casini Tin Whisker Investigation?
> > >
> > > The group that did this investigation met today to assign tasks for the
> > writing of the final report.  So, the final report is "in progress" but
> it
> > is not yet released.  (I am one of this group.)
> > >
> > > Each of the three radio-isotope generators has a high-rail at V+ and a
> > low-rail at V-, with a resistor bridge that establishes a connection to
> > ground, held between V+ and V-.  One of the three radio-isotope
> generators
> > has shown a sequence of soft-shorts: it is still able to deliver its
> power,
> > but it is shifting its off-set from ground -- this has not been a
> problem,
> > yet.  This behavior has been seen on a few other radio-isotope
> generators:
> > it is probably not of direct interest to most industries.
> > >
> > > The CAPS instrument has show a sequence of soft-shorts in distinct
> > locations.  Each has 'cleared' after various durations of elapsed times.
> >  Another has just appeared after the recent turn-on.  The instrument is
> > still working, and the shorts do not draw so much current as to cause
> harm.
> >  But no one likes these, and folks wonder whether one of these will jump
> to
> > a "hard short".  The specific concern is that such a hard short might
> harm
> > the power system and thus kill the other instrument.
> > >
> > > We never found an explanation for these radio-isotope events, or for
> the
> > soft shorts in CAPS, that had the sweep smell of "Yes!  That has to be
> the
> > reason!"  We have found tin whiskers growing from tin-plated transformer
> > cans of the precise type used in the CAPS, when we inspected similar
> items
> > still on the ground, and we showed that the shorting/clearing behavior of
> > these whiskers were consistent with the observed "soft shorts" and also
> the
> > time-dynamics of the coming/going of these soft shorts.  So, we supposed
> > that tin whiskers were a possible cause.  While we considered many
> > alternatives, some of which were also plausible, it was the whiskers that
> > seems the least objectionable.
> > >
> > > See the "tin whiskers (and other metal whiskers)" web site run by GSFC:
> > http://nepp.nasa.gov/WHISKER/
> > > This site illustrates many many horrors that have been rigorously
> > established to be caused by metal whiskers.
> > >
> >
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