Re: tlug: strange machine part 2

[Rex Walters <rex@example.com>]

On Wed, Mar 04, 1998 at 09:38:05AM +0900, Scott Stone wrote:
> On Wed, 4 Mar 1998, Uc^ida Masatomo wrote:
> 
> >  Need to check power supply or case.
> >  In Japan they use 100V, while most power supplies are designed for
> > 115V, which is used in U.S. So combination of power supply and mainboard
> > causes a problem.
...
> >  It's not rational. But it often happens in Japan.
> 
> Really.  That is interesting.  We've brought quite a few machines over
> here from the states and none of them have done that... oh well, I have an
> extra case or two here, I'll try that... thanks.

Most PC power supplies I've seen are not autoranging, and many are
designed to +-10% margin.  Running a 110VAC power supply at 10% below
nominal will usually work but leaves you *NO* margin.  That is, it'll
probably "work" most of the time, but you risk the DC side regulation
going way out of wack with the slightest noise or load.  

If I were a bungee (sp?) jumper I'd be ve-r-r-r-y leery jumping after a
big lunch with a cord labelled "190 lbs +/- 10%".  :-)

A step-up transformer on the AC input should be all you need.  If you
get a really big honking soft-iron core transformer you get some
additional regulation and can probably survive minor brown-outs, etc.,
too.  (I'm told, though I haven't measured, that power is pretty clean
here in Tokyo.)

I can't imagine a motherboard caring about what AC mains it's ultimately
powered from -- everything's 5 and 12 VDC, right?  The only issue is the
power supply itself.  Unless it is explicitly labeled 100VAC (not 110 or
115 V) I wouldn't plug it in without a tranformer.

And of course, power regulation may not be the problem.  It's like faith
healing.  With a miracle cure, one of three things can happen:  the
patient gets better ("Hallelujah!"), the patient gets worse ("Need more
cure!"), or the patient dies ("If only we'd got to him in time!").  :-)

Cheers,
-- 
Rex
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