Powering up a 20-year old MicroVAX II

[Brent Hilpert]

"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.