Just out of curiosity...

Capacitors just fail, it was probably one of the millions made with the faulty electrolyte several years back.

For some strange reason, switchmode power supply designers have a predisposition towards putting any and all critical electrolytics, as close as possible to any sources of heat that are also on the board.

This has the effect that from day one of the power supply's service life, its electros are being baked by external heat radiation from these sources. Now add to this that the caps that are fitted are often only 80 degree types, and are not of the best quality low ESR type specially specced for switchers, and you now have self-heating to add to the equation, when they start trying to handle the large high frequency ripple currents that many of them will be required to do, as part of their job. Now compound the situation even more by putting the supply in a unit tht's designed for its external appearance, rather than airflow around its inside, and finally put it in a glass fronted cabinet with poor ventilation in your lounge, and you can see why the electros will start to fail and eventually bulge.

Depending on where in the circuit the cap is, the failure may cause anything from a simple supply shutdown, to a catastrophic cascade failure, involving semiconductors and resistors on the supply itself and, sometimes, serious failures of LSIs located elsewhere in the equipment, due to either the power supply's regulation going out of the window, or huge high frequency ripple voltages on the rails, that these devices just can't handle.

These days, this type of failure is the 'bread and butter' work of most independent service engineers, so this mechanism of failure (which is not confined just to power supplies either) is very well understood by us all.

Arfa

I see/read a lot about SMPS failures and my educated opinion is that they are just very hard on components. Electrolytic caps are more susceptible to problems with heat which they seem to endure in an SMPS because of their physical placement next to heat sources. It also depends on the quality of the caps. Vendors sometimes use less than desirable quality caps that swell and blow for seemingly no detectable reason.

Thanks, all, for the input. As the result of all your feedback,I feel I have a much better grasp of what I am likely dealing with.

Much appreciated...

Dave

I had a video card blow 3 out of 6 electrolytics (unknown brand) in less than one year of use:

OTOH the power running this computer is nine years old and doing fine (Japanese caps).