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Starting a power supply without a motherboard.....

T

The Pentium Guy

Diamond Member
The unit's some Compaq power supply that doesn't have an On/Off switch.
The trick to turning on a PSU without a motherboard is to connect the green and black wires:
http://wiki.extremeoverclocking.com/wiki/Power_Supply

Meh, this thing doesn't have a switch. I do this and nothing happens. The computer's from at least 3-4 years ago and it had Windows 98 on it, so it's an AT power supply instead of ATX.

Anyone know how to deal with these older units?

Update: it's green to black, but the PSU switches on for a fraction of second, that's it.

-The Pentium Guy
 
Wait... it's an AT?

So it has TWO connectors for the motherboard and not a 20-pin connector?

If it's AT, it HAS a mechanical switch it plugs into. I think you might be mistaken.
 
Double check the pinouts with this site: http://pinouts.ru/pin_Power.shtml

Sometimes the turn on isn't green. I've seen it purple, blue, gray. If you have ONE WIRE that's a different color than ALL of the rest and it's in the same place as where a green would typically be, it's probably the turn on lead.

Remember, you're not going to hurt yourself jumpering the wrong pins. Even if it's 12V to ground. Because the pins aren't live UNTIL you jumper the correct pair.

Godspeed!!
 
After some testing, I guess it is green. The power supply turns on for just a fraction of a second and then switches off immediately. I only noticed this because the fan in there moves a slight bit and then stops. I checked and made sure the contacts were secure, it's not loose contact or anything...

I think what the power supply needs is a voltage 'jump' of some sort to keep it going. I'm not 100% sure what though.
 
If the PSU has any fan leads, try hooking up a fan to it so it has a current draw. Just make sure it isn't a super high speed fan if its not secured to something.
 
some older power supplies dont like running with no load and will shut themselves off. try putting a load on 5 and 12 v and trying it, like hooking an old hd up to it and try it.
 
You have to short the green with the black and leave it shorted. Be sure you have something else connected to the PSU because power supplies do not run happily without a load.
 
Originally posted by: The Pentium Guy
There's a 50W peltier attached to it...
Click to expand...

Just a thought, but on my 24p Enermax PSUs, there had to be a load on specific lines for the PSU to work.
 
Hi, There seems to be some confusion here. An AT power supply has two 6 pin single row connectors with locks and a heavy 4 wire cable. It does not start when shorting any two leads together. The heavy cable is for a double pole single throw switch that turns it on even if not connected to anything except the wall outlet. An ATX supply has one double row 20 pin or 24 pin etc connector with a lock. It does turn on when the green is connected to a black. If you just touch the green to the black it only runs while they are touching. Leave them connected to keep it on. Hope this helps a little, Jim
 
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