Smoke on the Horizon... oh s**t!

From: Paul Koning <pkoning_at_equallogic.com>
Date: Thu Feb 19 18:23:52 2004

>>>>> "Tony" == Tony Duell <ard_at_p850ug1.demon.co.uk> writes:

>> Now, the questions: what the hell happened? Failures of tantalums
>> (I've witnessed) are usually due to reversed polarity: not only
>> are these particular parts long-term residents of the boards, but
>> the unregulated +12V supply is the highest DC voltage in the
>> machine - how did the - terminal (DC

 Tony> FWIW, I've just had tantalum capacitors explode for no good
 Tony> reason. In once classic (!) case, I took an IBM CGA card from
 Tony> the box of PC bits and plugged it into an expansion slot. One
 Tony> of the tants (a decoupling cap on the 5V rail) exploded, but
 Tony> the board carried on working, the right image came up on the
 Tony> monitor, and the machine passed the POST.

A good way to have your tantalum cap explode is to install it
backwards. That happens occasionally even in products manufactured in
volume -- the robots are not 100% foolproof. It may take a while for
this to happen.

Then again, they also fail due to age, and typically fail shorted. It
turns out there are tantalum caps with built-in fuses. You'd use
these in cases where you don't want to have the downtime resulting
from shorted caps.

     paul
Received on Thu Feb 19 2004 - 18:23:52 GMT