Too high ripple current?? I have seen switchers which
parallel several lower value caps to get ESR down and
handle high ripple currents.

Could it have been one of the 'bad electrolyte' caps
made in the 2001 that caused so much grief with mother
board makers (and caused 100ks of board failures in the field)?
Look for "'bad capacitor' electrolyte motherboard" on google for
the details. e.g.

http://www.spectrum.ieee.org/WEBONLY/resource/feb03/ncap.html

"It has all the elements of a good thriller: a stolen secret formula, 
bungled corporate espionage, untraceable goods, and lone wolves saving 
the little guy from the misdeeds of multinational corporations. In this 
case, a mistake in the stolen formulation of the electrolyte in a 
capacitor has wrecked hundreds of PCs and may wreck still more in what 
is an industrywide problem.
....
Most of the leaking capacitors pulled from bad boards in the United 
States, according to repair people, were labeled Tayeh, not a brand 
affiliated with known capacitor makers. Many others were unmarked.
"
======================

This is exactly what has happened to several of my 2002 vintage
Gigabyte boards.
http://www.spectrum.ieee.org/WEBONLY/resource/feb03/ncap01.jpg

R

Dave VanHorn wrote:

> At 01:28 PM 11/24/2004, Olin Lathrop wrote:
> 
>> PicDude wrote:
>> > Late last night, while building a 3-output power supply, a capacitor
>> > burned out (it just made a poof sound and the electrolyte leaked out)
>> > and it's totally baffling me.
>>
>> Most likely possibility:  The capacitor was in backwards.  They do 
>> take it
>> for a while, then BOOM.  I know you said you checked this.  Check it 
>> again.
>> I still think it's the most likely explanation.
> 
> 
> How is that output regulated?
> 
> I've seen flyback switchers do this where the regulated output has a 
> heavy load, and the unregged outputs voltage went higher than the 
> designer anticipated.
> 
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