H7140 PDP 11/24 Power Supply Advice

Gee, how about another post on this thread that actually relates to the thread... 8^) Funny how that happens on mailing lists. 8^) After a little looking and digging, I discovered that the capacitor that failed is a Sprague series 672D -- indeed designed for switching use. Newark had 12 of them left, so I ordered 2 of the "real McCoy" just for authenticity, though I am sure I could have easily found something adequate locally for a lot less money. In the Newark catalog illustrations and descriptions, their is NO MENTION of that third ("extra") axial lead from the aluminum can (that goes off to the working return -- the 300V Return). I am guessing that either DEC welded that extra lead on the aluminum can (or had Sprague do it as a special order) as a safety against shorting to the heatsink of the transistor next to it. [Since the board is currently buttoned-up inside the power supply, I cannot easily look without some effort -- I cannot remember for sure if that heatsink was running to chassis ground or the +300V return, but I am guessing chassis ground]. If it shorted, it would short to the 300V return, rather than to a floating can -- which, if the transisitor heatsink is strapped to chassis ground, would put +150V or so between the can and the inside of the capacitor -- presumably with "spectacular" results. Then they put all of that in heat-shrink outside the original plastic wrap on the capacitor. How would one go about duplicating that feat? One thought that had occurred to me was to just try (say, with heat shrink) to get a third lead in contact with the outer can surface -- by taking off the factory plastic wrap, taping on a wire, and then heat shinking that in a new cylinder. It would not be a real sound connection, but it presumably would be better than nothing. Jay At 07:09 PM 11/13/2001 +0000, you wrote: <<snip>> --- Jay R. Jaeger The Computer Collection cube1(a)home.com visit http://members.home.net/thecomputercollection