Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!nancy!wsrcc!wolfgang
From: wolfgang@wsrcc (Wolfgang S. Rupprecht)
Newsgroups: sci.electronics
Subject: Re: Power supply for IBM PC interfacing projects
Message-ID: <1990Sep12.142550.9853@wsrcc>
Date: 12 Sep 90 14:25:50 GMT
References: <15286@shlump.nac.dec.com> <1990Sep12.021220.11551@swbatl.sbc.com>
Organization: Wolfgang S Rupprecht Computer Consulting, Washington DC.
Lines: 26

adams@swbatl.sbc.com (Tom Adams - 235-7459) writes:
>Could someone explain what a PC power supply needs connected in order to
>function?  I've tried to use old PC supplies on the bench and can't seem
>to get any voltages out. 

I have just such a gem here.  The trick is that on cheap imports, they
just assume that the 5v has some moby load on it.  The Taiwan clone
"200w" KPI supply I have needs a 1 ohm (25w)  load on the 5v to work
well.  Well defined as the 12v supply actually being within 10% of its
rated voltaage. ;-(

With no load the thing goes into over-voltage trip mode.  With a small
load of 1/2A, it does power up. It just has poor regulation on all
supplies.

You see it looks like there is really only one regulator in this whole
box.  They just assume that all supplies track, and you will naturely
want to draw at least 5A at +5v.  aaaaaarrrrgggg!  

Anyone have a brand name for a PC supply that actually *would* put out
12v @ 3A without wasting 25watts at 5v?

-wolfgang
-- 
Wolfgang Rupprecht    uunet!{nancy,usaos,media!ka3ovk}!wsrcc!wolfgang
Snail Mail Address:   Box 6524, Alexandria, VA 22306-0524