[mdlug] Old 386 needed - Power Supply

[Jay Nugent]

Greetings Ray,

On Tue, 21 Apr 2009, Raymond McLaughlin wrote:

> Jay Nugent wrote:
> > Greetings,

    ...snip...

> Thank you Aaron and Jay,
> 
> I have been, and continue to mull a more detailed reply, but will here
> quickly point out that I have, on hand, several serviceable AT and ATX
> powers supplies. Each of these provide both a +12 (yellow) and a -12
> (blue) output. Shouldn't this look like 24v to any DC device connected
> to it? 

   CAUTION.  The +12 and -12 are referenced to the ground lead -- and this
is oftentimes directly connected to the chassis of the power supply as
well as the motherboard.  Sound ground *MUST* be isolated between the
power supply and the PC/laptop if you expect this to work.  Never the two
shall meet :(

 
> Just quickly, shouldn't the 24 volts described above provide a
> satisfactory "first approximation" of the 22 that the laptop requires?

   I would expect 24 volts would work fine.  24 is within 10% regulation 
of 22 volts.  I would find it unlikely to cause the magic smoke to escape.
Be carefull though...many wall-wart supplies may "say" that they are 24 
volts, but they usually mean they will *produce* 24 volts at rated load.  
At less than rated load they *may* produce a much higher voltage.  Always 
measure with a meter BEFORE connecting the laptop to it the first time.
 
      --- Jay

Train how you will Operate, and you will Operate how you were Trained.
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