Marko Vojinovic wrote:
On Wednesday 20 August 2008 15:14, Ed Greshko wrote:
What motherboard are you talking about...and what time frame are you
certain was the time when it was manufactured with faulty capacitors?
What I know is not precisely for one specific type of motherboard. It's just
that during the Pentium II / III era it was like general practice to put
cheap capacitors on motherboards. Note --- *cheap*, not faulty. This means
that the lifetime of some capacitors was as a rule far shorter than that of
the motherboard, and the outcome was that motherboards often needed
replacement after a year or so.
Those caps were faulty besides being cheap, the company making them tried to
"borrow" a "design" from someone else and the design spec they borrow was
missing additive(s) that resulted in the caps having a much much shorter life.
There was discussion at the time of whether the borrowing company got an early
unfinished design, or whether the company with the working design "passed" them
a design that was good enough to pass initial test and fail down the road.
See: http://www.geek.com/capacitor-failures-plague-motherboard-vendors/
And besides the p2/p3 era failure, a second failure from an expensive cap maker
came along a couple of years after that and hit Dell and Intel MB's, Dell took
write downs on the company reports of about US$270,000,000 that quarter. This
was for the caps being faulty because they were overfilled (the formula was
correct).
See: http://en.wikipedia.org/wiki/Capacitor_plague
And as of 2005 there were still bad caps around as I have a video board with
several bad ones one them that should have been built *AFTER* both of the
above events (9/2005, the Dell event caps were built in 2004), and failed 4 of
the caps after around 3 years of usage.
.
Also, while my knowledge on electronics is fairly limited, I believe that
capacitors are the one type of component on the motherboard that is most
likely to fail after some time. Resistors, transistors and ICs have much
bigger lifetime, in my naive opinion. And the very role of capacitors --- to
iron out peaks in voltage or whatever --- puts them on the front line for bad
external conditions.
The caps with liquid in them have at best limited lifetime, though if built
correctly will typically last longer than needed, a number of the MB makers are
going to solid caps with no liquid in them just because of how difficult it is
to make a small high capacity small liquid capacitor with a long life. If they
did not have to be small, high capacity, and long life all at the same time
there would not be an issue, making them physically larger would have reduced
the stress on the component and increased the life.
Oh, and you can know that a capacitor failed by visual inspection (if it is
deformed in shape and/or has traces of electrolyte flowing out) or by taking
it off the motherboard and using an ohm-meter.
Generally it is obvious on visual inspection, especially if there is
liquid/crusty material on the cap. Also if you have several identical ones
and some of them look different that is a bad sign.
Roger
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