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From: inuy@vax5.cit.cornell.edu
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Can an IBM power supply live on an Amiga 2000?
Message-ID: <1990Nov10.132754.933@vax5.cit.cornell.edu>
Date: 10 Nov 90 17:27:54 GMT
References: <7652@cica.cica.indiana.edu>
Distribution: na,comp
Lines: 55

In article <7652@cica.cica.indiana.edu>,
graham@venus.iucf.indiana.edu (JIM GRAHAM) writes:
> In article <90313.094443MBDZM@ROHVM1.BITNET>, MBDZM@ROHVM1.BITNET writes...
>>Can I hack an IBM a/t supply (about $50) to work?
>
> Yes you can.  I've done it.
>
>>The voltages seem to
>>be ok +5, -5, +12, -12, but there is a line marked "TIC". That is the one
>>I can't figure out.  Is it there on the IBM supply? Can I fake it?
>
> Darn! Wish I had my notes with me.
>
> I can't remember what the TIC line is all about.  I do remember that I
> did not have to worry about it.
>
> On my supply, there were several identical connectors (all with 4 pins).
> Additionally, there was one long connector which normally went to the
> mother board of the pc.  This connector was the one with the "TIC" line.
>
> I am presently running an Amiga 500 with A501, external floppy,
> two (2) Seagate ST238R HD's, Omti controller, and interface between
> the A500 and the controller off this single supply, and it doesn't even
> get warm.
>
> It is NOT a stock AT supply.  It's from some mail-order company.
>
> When I was playing around with the hookup, I learned that it has internal
> "sensing" of the load (which, in my opinion is not exactly efficient...
> the load should be "sensed" AT THE LOAD).  However, it regulates very nicely
> and I'm quite happy with it.


A few notes on PC power supplys.

First, I have yet to see one that uses remote
sensing.  This ensures the voltage is correct at the load by compensating for
any voltage drops in the wireing going to the load.  While this sounds like a
good idea **VERY** nasty things happen if the senseing wires become
disconnected while the power supply is connected.  The power supply suddenley
sees the load has no voltage being applyed to it, and it begins cranking the
voltage up trying to compensate for the 'losses' in the connecting wires.  WHat
winds up happening is the power supply cranks the voltage up full boar,
sometimes with very nasty results.  Best bet is to jumpre the sense and output
terminals right at the supply, and use haevy wire going to your load.

Next, most PC style switching power supplys do not like being ran without a
load.  I have a 'dummey' device that consists of a few 25 watt power resistors
that draws about 2 amps off the 12 volt line, and about .75 amps from the 5
volt line.  This seems to be a good combination.

Last, if you where wondering, the PG line on a PC power supply stands for power
good.  It goes high once the power supply has stabelized after turning it on.

Matthew Kleinmann