PSU Go Pop - So why does this happen?

[mwtb]

The Antec PSU on my server box just let go with a quiet bang and the mains plug fuse blew out too (twice in fact, seeing as I replaced it and checked if the PSU would run on by itself). I guess time will tell if anything else went with it.

I've already ordered a new PSU, so this isn't the usual "spec me" thread. I was just wondering if anyone had any insight into why this happens. I mean, the PSU was a few years old and I run the server 24/7, so I'm not surprised it failed, but what is the mechanism outside of a short? Why do they go pop? What is the life-expectancy?

 

[mwtb]

To answer my own question a little. The MTBF of the Antec seems to be 80000 hours, or a little over 9 years. I guess I'm on the unlucky end of the range.

 

[mwtb]

The most likely part of a PSU to fail are the capacitors...

Thanks for a great answer. I guess I may get into the habit of having a spare PSU around. I'm up to three PCs in the house now, and it seems likely that one of them will fail every couple of years.