[robespierre]

For what it's worth, I would change all of these foil capacitors even they look OK. With age they suck up humidity and crack. And then they blow. You can find them in PowerOne PSUs from the PowerSeries as well and lots of them were cracked. You can still buy them from Farnell etc. Kemet makes them.

They aren't made of foil, but metallized paper, part of why they absorb moisture so readily. They are used to reduce electromagnetic interference (EMI) radiated or conducted out of the equipment; they aren't necessary for any aspect of the equipment's function. The "X2" is a rating class for capacitors used "across the line" (from live to neutral) as opposed to "Y2" class which are used between current carrying conductors and protective earth. Since the PME paper capacitors have such a bad reputation, they are not widely stocked and are rather expensive as a result. They can be replaced with polypropylene film types with the same dimensions and ratings.

Back in the 1980s, RIFA AB in Sweden advertised its capacitors as being safer from fire, shock, or transient damage compared to competitive types. The vulnerability to moisture was never mentioned.