Powering up a 20-year old MicroVAX II
hilpert at cs.ubc.ca
Sun Mar 1 23:25:03 CST 2009
"Roy J. Tellason" wrote:
> On Sunday 01 March 2009 10:36:33 pm Brent Hilpert wrote:
> > "Roy J. Tellason" wrote:
> > > > If it was plugged in but not switched on and something popped, it'll be
> > > > the mains filter cap. They *do* fail, and they're easy to replace.
> > >
> > > In seeing photos of this in the process of dealing with it offlist, it
> > > looks exactly like that's what it was. When I asked about the markings
> > > on the failed parts I was told that they included "250V", which is way
> > > inadequate for UK mains voltages...
> > That's not necessarily a flaw: 120/240 supplies often do the voltage
> > selection by switching the circuit between bridge rectifier for 240V and
> > voltage doubler for 120V. In the bridge config two caps end up in series,
> > so 250V+250V=500V.
> Not if the config is the two caps being across the line, before and after the
> typical inductor that's also commonly a part of that filter...
> The series connection is usually the two _main_ filter caps, not the line
> ("mains") filter components.
OK, (you've seen the photos), I thought the ealier poster might be alluding
back to the electroytics discussion, so just threw in the comment.
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