[no subject]

The definitive diagnosis is that when it goes, there is a really strong
odor. 

It's typically a 0.1 to 0.25 uF capacitor rated for 600 VAC and with an
"X2" type (self-healing, rated for line filter use). 

If your supply has two input filter caps (right after the bridge
rectifier), then the supply might still operate if one of them failed open.
But I doubt it. Losing the input filter cap will almost certainly shut the
supply down, since it will drop the average DC input voltage by 30%-50%,
which is enough to drop the supply out of regulation. 

BTW, the input filter caps will be bled to a quite low voltage within a few
seconds. But you should always short an electrolytic before working on it,
just for good measure. If it is retaining a charge you'll get a nice "pop"
when you discharge it--all perfectly normal and harmless. 

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon