Emily DeSchanel could not have said it better.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE)
Sent: Monday, March 26, 2012 12:07 PM
To: [log in to unmask]
Subject: Re: [TN] More Information on Casini Tin Whisker Investigation
So would that be the saw shank redemption?
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards
Sent: Monday, March 26, 2012 9:53 AM
To: [log in to unmask]
Subject: Re: [TN] More Information on Casini Tin Whisker Investigation
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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