> No problem with spikes or anything else untoward AFAICT, this
> particular regulator just decided to give up its day job

Well, maybe, but my experience with customers who have sudden unusual field
problems is that there's usually a very different explaination.  In other
words they're not going to tell you "We accidentally touched your gizmo to
the arc welder".  You're going to hear "It just went.  Nobody has been near
it for 3 years, and the whole time it was alone on a table on an anti-static
mat in a climate controlled chamber surrounded by 3 inches of lead
shielding".

Many years ago I worked for a company where the main (and only) computer was
a Prime 750 time sharing system.  Although it wasn't my real job, I was
usually the guy that would have to deal with computer failures.  They were
much more common in those days.  Average up time for the whole system
without incidence was probably just a month or two.

Early one morning I came in to find the system dead.  After some poking
around I isolated the problem to the serial lines board.  I pulled the board
out and saw a scortch mark the size of a quarter at a particular chip.  I
traced it back to figure out what serial line it was, then went to find the
other end.  This turned out to be 100 feet away in the production area.  I
found the end draped over a piece of supporting metal of a CRT monitor that
had the cover removed.  The end was dangling a few mm from the CRT's socket,
so it was pretty obvious what had happened.  Later when the production folks
showed up, I asked them about it.  Would you believe that despite the
smoking gun evidence that nobody had been near that setup for days?  Funny
how some of them knew to protest no knowledge before I had a chance to ask
them what had happened.


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(978) 742-9014, http://www.embedinc.com

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