Re: Deskpro EN: No Power

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Has anyone used a compaq power supply on a 20 pin atx motherboard?  I
bought one
of those 24 pin to 20 pin adaptors and most everything
looks in order except for
a few of the pins.  Are any of the 3.3 or
-12 volt pins on the compaq power
supply supposed to mix with any of
the other 12 volt or 3.3 volt pins on the 20
pin side of the


Re: Deskpro EN: No Power

On Thu, 11 Aug 2005 23:31:17 GMT, (mstngGT_chris_01)

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I may've missed the front-end of this thread but there are
two general types of Compaq PSU i've seen used in the past
few years.  One is a standard ATX and the other is a
proprietary (pinout, but comes in several different wattages
and systems) unit that cannot be used on any other standard
motherboard.  I don't know exactly what your adapter is like

You won't "usually" need -12V on any remotely modern
motherboard.  Some Compaq PSU had a 3.3VSB (standby) power
rail that is not connected (do not connect it) to any
motherboard rails, not to the main 3.3V power rail either.

The best thing to do is plug an AC cord into the Compaq PSU
and take voltage readings on all wire-groups (colors).  Note
what's live without the PSU being plugged into anything (Not
even the motherboard) and which pin #s these live pins are.
Compare that to a standard ATX which should only have power
on the 5VSB and PS-On pins.

With the Compaq PSU connected to nothing but a HDD on one of
it's 4 pin connectors, see if you can determine the 5VSB pin
and jumper it to any ground lead with a paperclip.  The PSU
should then turn on, it's fan spinning and the connected
drive spinning as well.  If you can't get it to at least do
that much without it connected to the motherboard, there is
no point in trying to run the motherboard at all as that is
similar enough to the environment needed when the
motherboard would turn the PSU on.

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