Look, it's just a switching mode power supply.  There's no magic about
attaching a motherboard.  The reason Ben's trick below works is because
sometimes they cross couple the current limiting / protection circuitry. 
Some chips that require both +5 and +/-12 will die if one rail dies, so the
conservative P.S. designer will kill the whole supply rather than let one
rail stay up and kill chips.

An incandescent bulb is a bad choice, though, because they are usually 1A
bulbs, and you're probably drawing a lot more current than you need to keep
the supply on (and making heat, and reducing the available power you have
at your disposal before you eat a fuse.)  Probably a 1k resistor is more
than sufficient.  If you can, get a potentiometer, and find the minimum
value that keeps the supply alive and then add 15-20%, and there you go. 
15 minutes with a voltmeter, and you'll have a bunch of wimpy but utile
bench supplies!

Phil Mendelsohn

On or about 20 Jun 2001, Ben Kochie is alleged to have said:
> -----BEGIN PGP SIGNED MESSAGE-----
> 
> there are some supplies that don't like to power up unless there is
> something attached.. sometimes sticking a small 5v and 12v light bulb on
> some of the motherboard output lines can do the trick.
> 
> Thank You,
>         Ben Kochie (ben at nerp.net)
> 
>  "Unix is user friendly, Its just picky about its friends."
> 
> On Wed, 20 Jun 2001, Brian wrote:
> 
> > Here at work we often have to scrap old non-booting systems.  I'd
really
> > like a nice 12 volt power supply at my desk but I don't want to have to
> > attach a mobo to it.  Is there any way to get the power supply to run
on
> > its own?
> >
> > The only info I can find is for ATX power supplies (which is as simple
as
> > jumpering two pins together with a paper clip) but nothing on AT power
> > supplies.  Anyone have any idea how to accomplish this?
> >
> > And yes, I know they say not to do it because you may damage your power
> > supply, but I have an overstock of these 145 watt units so I don't care
if
> > I destroy a few trying :-)
> >
> > -Brian
> >
> >
> > _______________________________________________
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> > https://mailman.mn-linux.org/mailman/listinfo/tclug-list
> >
> 
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