Okay, I had a look into the cookie-tin just now.
Yup, that particular capacitor is bulging quite a bit on top, as are about four similar ones of the same brand elsewhere in there.
I wonder how much longer I can ignore them?
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Well, that question was answered this past week, just
after I departed for a rock-climbing trip.
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The system started crashing with various random errors, and SWMBO did her best to keep rebooting it in attempts to try and maintain internet/email access in my absence.
Now that I'm back, the hard disk has been moved to another machine to restore service -- I've actually just hooked it up via USB to a small notebook computer, along with a USB ethernet adapter to provide the second network port. Works fine!
Meanwhile, I now have to order some new caps from digikey to refurbish the mini-ITX board.
Cheers