Can an unswitched power supply work on a MB that came with a switched PS?

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mojave

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Dec 24, 2002
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I'm in past my abilities on this one. Can a 400 W Antec ATX 12V power supply, unswitched except for an on/off switch on the back, work on an old Amptron motherboard, a PC that came with a switched power supply?

Background: I'm having strange system crashes plus intermittent "blackouts", the PC turns off and on by itself (no flicker from the desk light attached to the same outlet). I'm thinking maybe I need a new power supply and go to my local computer store. They have no switched power supplies, which is what the PC was built with 5 years ago. I got the Antec, thinking it might work, get home and put it in the PC. Nothing. Completely dark. The on/off switch on the back does nothing, no fan, no power.

It looks like the power supply is looking for a signal from the motherboard to go "on". I may just need an explanation of how switched vs. unswitched power supplies work.
thanks!
 
Joined
Sep 1, 2004
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1,756
I don't think you're talking about switching vs. non-switching powersupplies, a switching powersupply is one that can auto-detect whether the input AC voltage is 110V or 220V. I think you mean that your old computer had an AT powersupply, and you want to know if it can work with an ATX one. Your motherboard must have both AT and ATX powersupply connectors on it, for your new one to even fit. An AT powersupply has a shielded powercable leading to a switch that goes behind the powerbutton on the front, it hooks up to that with 4 wires. An ATX powersupply relies on two pins on the motherboard being shorted (they get connected to a powerbutton on the front that doesn't carry current, unlike the AT powersupply that carries a dangerous mains voltage line through the middle of the case). It sounds like you have an AT case, I would suggest transferring your motherboard to a new ATX case and hooking the front powerbutton on the ATX case to the power pins on the motherboard, they will be alongside the hard disk LED, reset, power LED etc. pins. There will be a 2pin plug named "power" or "ATX power" or something like that to make this connection.
 

JohnWill

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Oct 19, 2002
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106,429
I suspect the answer is no. Too bad, I have a bunch of those old AT supplies in my closet. :D
 

mojave

Thread Starter
Joined
Dec 24, 2002
Messages
7
Thanks, you guys. Yeah, I don't even know what I'm doing trying to keep a 5 year old computer alive. Arcadion, I'm going to be following your advice exactly except it's going to be a new mobo & CPU.
 
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