Electrolytic Capacitors & PSU Failure
I totally agree with Nick Nielsen. One of the reasons there are strongly worded warning labels on a PSU is because of the electrolytic capacitors, which can hold and maintain a large amount of D.C. current even though the PSU has been unplugged from power and completely removed from the system.
One of the dirty tricks I heard of in electronics class was to put a full charge into a large(D-size battery size), then touch it to some unwitting student's wrist. The shock is brief, but quite grueling, especially if the cap is from an old-fashioned, vacuum-tube T.V. or radio, which ran at much higher voltages.
If the read the find print on these devices, most are rated for a maximum voltage of 600 VDC. So a good size surge is enough to max one split open.
In the old days, when PSU's were very expensive, and when I had a de-soldering station, I replaced many caps. Now, with the cost of labor versus the cost of a new PSU, it is difficult to justify the time to do almost any board-level repair, and that extends to motherboards.
While over-heating is frequently the cause, I would guess that most PSU failures are the result of lousy A.C. power input.
Sorry to say so little in too many words...
Aloha from Hawaii,
Glenn
