Can I rewire a switching power supply to use with an ancient motherboard?

[Larry Mudd]

I made an impulse-expenditure of $5 at a computer swap-meet today, for a shiny new power supply.

The idea was to drop it in the creaky old pentium I keep in the other room for web-browsing, .mp3 playing, and the occasional head-to-head Starcraft session. It's picked up the habit of sounding like a dying elephant for the first half-hour or so that it's turned on -- so I tend not to turn it on.

Now that I've got home, I noticed that my new purchase is a switching power supply, and said creaky old pentium does not have a motherboard which supports such new-fangled craziness-- it has the old school 12-pin AT PS sockets.

Can I get away with spoojing the leads from the new PS onto the plugs from the old one, and just insulating the ends of the eight "extra" wires?

The colour-coding is conveniently the same, although the red leads have a lower amperage in the new PS -- 5v/20a, down from 5v/23a.

Is this likely to be doable? Or should I bother?

My intuition is that it should work fine, but I'd appreciate input from folks with a more solid electronics background.

[Larry Mudd]

...I see that some of the "extra" wires are for the switch..

I'm guessing if this were to work at all, I'd need to connect the green wire labeled "P.S. On" and one of the grounds to the power switch. Would this work?

Also, what about the reset button? And what is the wire labelled "P.G." for?

[Q.E.D.]

Even the older AT power supplies were switching power supplies. It sounds like what you have there is an ATX power supply, which AFAIK, is incompatible with an AT mainboard. For one thing, the ATX supply has a wire called POWER_GOOD which tells the PS that the mainboard is happy about the volatage levels. However, there are Pentium-class AT form-factor mainboards that have both ATX and AT connectors, and will drop in to your existing case, and they're failry cheap.

[Larry Mudd]

Thanks, Q.E.D., for saving me some futile tinkering.

I've been planning to upgrade my main computer in November-- I'll probably end up dropping its old mb in that case.

[Larry Mudd]

Mwaha!

A more elegant solution to my immediate problem presents itself--
I'll just cannibalize the muffin fan from the new one for use in the old one-- they're exactly the same.

Two wires to splice instead of twelve -- and no doubt that it'll work. :smack:

My $5.00 investment has not been in vain.

[Larry Mudd]

And by god, they're socketed.

[ftg]

Old AT PS's are dirt cheap. My local Goodwill sells them for $3 used. A new once could cost a whopping $10. Note: don't test them without a load. Plug it into a HD and old MB to test.

I have seen the opposite connector: Adapts an AT PS for an ATX MB. I don't see how they would work. Since they're about $8, even if a ATX->AT connector existed, it's cheaper getting an AT PS.

If it really is just the fan though, replace it.