Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!unmvax!gatech!cwjcc!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: sci.electronics
Subject: Re: DC power supply for IBM PC?
Summary: Why not by a stand-by power pack and use it?
Message-ID: <1650@neoucom.UUCP>
Date: 2 Jun 89 11:41:01 GMT
References: <4682@drivax.UUCP> <1989May28.214142.26384@utzoo.uucp> <4694@drivax.UUCP>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 41


Since a 12-MHz AT-clone is being discussed as the target system,
volumetric efficiency must not be a terribly high priority option
in specifying the system.

What comes to mind is using a stand-by power pack that would
normally be used for AC power failure protection.
My questa stand-by power pack already has lugs on the back
to accomodate an external 12-14 volt DC source in lieu of the
internal battery.  The questa is about the width and height and
about 2/3 the length of an average shoe box; it puts out 200 watts
for 20 min., which is the life of the internal battery.  My
particular unit has to be derated to 150 watts for continuous duty
from external power.

150 watts is more than enough for an AT-clone and monochrome
monitor.

By the way, questa is a fairly high-priced brand; you can probably
do better by shopping around, but you might want to check to see if
the unit under consideration already has an external DC input to
save you the bother ov having to kludge it yourself.  I got my
questa at a close-out sale for $100 from a dealer who thought it
was only a filter of some kind.  A rough guideline for shopping is
about US$1 per watt out max output.

One other alternative is to go buy the Tandy LT-1400.  It has 768K
meory two 720K drives, full ports, drives external kbd/monitor,
etc. and has been "discounted" to $999 list.  With our
corporate/educational discount of 15%, I can buy it for $849.95,
which makes it difficult to resist.  The CPU, is only a 7.16 MHz
V20, but that seems in keeping with the bulk of computational
demands that are placed on a _portable_ machine.  I seldom have
need to do complex ray-traced rendering while riding in my car...
The pctools program rates the LT-1400 at 1.6 the performance of a
standard 4.77 MHz XT, which is about what the subjective feel is in
normal operation too.


Bill
wtm@impulse.UUCP