[sdiy] Resistors -- (was: prophet 600 weirdness)

[David Cornutt]

On Sep 17, 2004, at 12:30 PM, klosmon wrote:

> Good question, Michael:  what's the deal?
> I can understand a resistor in a high-heat situation (power supply, 
> etc)
> eventually burning out & either changing value or becoming an open 
> circuit;
>  don't really understand a working resistor suddenly becoming a piece 
> of wire.
> Anybody?
>

In my admittedly-limited experience, this sort of thing usually
results from the component getting internally contaminated during
the board manufacturing process, either during soldering or
during board wash.  I saw this years ago on a system I worked on
that had a bunch of Litton alphanumeric multi-segment LED
displays.  The engineering units worked fine, but on the production
units, the displays failed after about 60 days.  The manufacturing
people traced the problem to the flux remover used at the
factory; it ate up the pin seals on the displays and entered
the interior, where it slowly made everything inside fall apart.
They switched to a different flux remover and everything was
fine after that.