This is why gear which has been sitting around a long time should be 'eased' back into operation... especially minicomputers with large multiple power supplies: Electrolytic capacitors use aluminum foil for the electrodes, and aluminum oxide for the insulation between them. This insulation is formed on the surface of the foil by a chemical which is contained within the capacitor case, soaked up by porous paper wound up in the spool of aluminum. When the capacitor dries out, from a pinhole leak or heat or age, or if there is internal shorting, heat is generated. If the current is strong enough, the heat boils the chemical and that usually breaches the case somehow. Most electrolytics have a designed in 'safety-valve' of some kind or another, either a thin rubber plug in the can, or in the case of small PC-mount units, the case itself is scored with lines in the material, so it will rupture there first. Then the guts come spewing out with a bang, and paper bits and aluminum foil go all over. I have had this happen while bending over a board trouble shooting it; damn good thing I wear glasses because the cap-guts coated both lenses and would have gone right in my eyes. I have been around many of the darn things when they pop, and have seen some spectacular (and very dangerous) situations where the larger sizes have gone off and destroyed equipment in the process. My second PDP-11/04 ran fine for about two weeks, and then one afternoon the +15V regulator filters woofed their cookies simultaneously, one blew up and one hissed like a snake... it took two weeks to get the smell out of the house.... Then there was the 7805 TO-220 regulator on a Cromemco memory board I was fixing out on the bench... *it* blew up and embedded a sliver of epoxy in my cheek, as well as scaring the *%^&$ out of me... I didn't know I was wounded until blood dripped off my chin onto the board... I had to go to the emergency room and have it dug out.. what fun. The doctor was so fascinated that I was working on a computer at home (1978) that he kept stopping to ask questions about the machine, and what it could do, and.... But I'm getting off topic, no? Cheers John