Powering up a 20-year old MicroVAX II

[Brent Hilpert]

"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.