On 18 Nov 2012 22:48:22 GMT, "DoN. Nichols"
wrote:

On 2012-11-18, Pete C. wrote:

Spehro Pefhany wrote:

On Sun, 18 Nov 2012 09:51:00 -0500, the renowned "Pete C."
wrote:


wrote:

[ ... ]

On today's computers, with gold plated instead of tinned connections,
it is EXTREMELY rare.

Nope. I've personally seen it on $$$ equipment with top quality gold
plated connectors. Reseat those connectors a few times and the problem
goes away.

Sometimes it's a cold solder joint somewhere that starts working again
when the board is flexed and the oxidation is temporarily wiped.
Chances are it will come back in either case.

It never has in my experience. The last one was some equipment that was
unpowered for about a year and a half, lack of power seems to aggravate
the issue. The equipment was having odd issues when powered up again, I
powered down, reseated everything a few times and the problem went away.
The problem never reappeared in the next four years the equipment was
running.

Hmm ... if it was something made after the ROHS requirement came
in, and if the connectors were plated with pure tin to match the
requirements, the pure tin grows conductive whiskers -- quickly or over
long periods of time. Whiskers across pins in active equipment may be
vaporized, while those across unpowered equipment will just stay there
until it is powered on. If multiple whiskers bridge a given connection,
there may not be sufficient current to blow the whiskers away.

But yes, oxidiation in connectors -- sitting idle or in frequent
use -- can be a problem. My most frequent experience with that was the
motherboard of the SWTP 6800 home computer kit. The bus connectors were
each a row of fifty pins sticking up, and Molex connectors which slide
over those. About once a year I would have to open it up and pull each
board off and slide it on a few times to clean the oxide. A real pain,
but at least I knew how to fix it. :-)

Good Luck,
DoN.
There was a product made for that - can't remember but I think it was
de-ox-it. Put it on at assembly and NEVER have the problem. The
concentrate was over $30 an ounce over 20 years ago - but you mixed it
about 6:1 with ethanol and it went a LONG way.