The only problem you are lilely to have is associated with the actual DC voltage
present at that section just after rectification. 120VAC rectified and filtered
with caps produces a nominal 120*sqrt(2) or 170VDC.  Many good PC power supplies
will operate off of as low an AC voltage as 90VAC, giving the DC section a lower
limit of 127VDC, which MAY mean that you could put 125VDC in and it would work
out OK.

I wish you the best of luck, and please post your results here!

-Adam

Mark Peterson wrote:
>
> I need to power a PC from a nominal 125 VDC source.  The voltage may vary
> from 110 to 140 VDC.  I want a 300 W ATX supply that will be a direct swap
> with the existing 120 VAC unit in the PC.  I'm finding that this type of
> supply is very rare.  A couple vendors in China responded to my email
> inquiry stating that they would consider modifying their standard units.
> They lost interest when I told them I only need three or four of them.
>
> I've considered modifying a standard supply, which are abundant and cheap.
> I searched for schematics but found that they are nearly impossible to get.
> It appears that the first thing a standard ATX supply does is rectify the
> AC input, filter it a bit, and then present it to the switching part of the
> supply.  I'm wondering if I can simply connect the 125 VDC source just
> ahead of this switching section.  I'm going to do some experimenting but I
> wanted to check if anybody knows of a source of such a supply or if they
> have ever tried what I'm planning to attempt.
>
> Thanks.
>
> Mark P
>
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