How to turn on POwer Supply of computer without attaching it to motherboard?

Question

technically how does motherboard send signal to power supply to turn itself off when you shutdown.
And when I remove power supply from mother board and system, plug it in to power yet it was not turning on. The CPU power button might be touching one or several pins of the power supply to turn on. What are these pins???

I am refereing to an ATX system.

I would like to know this for troubleshooting purposes.

Thanks so much.

Answer 1

You want to read the ATX power supply spec at http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf.

The signal to turn on the power supply is called PS_ON#. Basically, short this to ground to make your rails come up.

See figure 11 to get the connector pinouts and wire colors. PS_ON# is supposed to have a green wire, and the grounds are black.

The old AT power supplies used to need a load to operate. You had to go find a huge resistor and place it between one of the supplies and ground for the PSU to come up. ATX supplies are more forgiving, and have this handy signal for this purpose.

--N.

Answer 2

DO NOT turn the supply on without it being hooked up to the computer. These supplies are designed to work with a load (the computer) hooked up to them. If you turn on the supply without it being hooked up you will burn it up and you will have to buy a new one.
The only way to test a supply is to keep it hooked up and use a voltmeter to check the output voltage.
If you do not know how to use a voltmeter I would suggest taking the supply to a computer shop and have them test it.
Hope this helps, Roy
For what it is worth. I don't know if anyone comes back and reads these things or not but I was wrong. I was thinking about the old supplies and wasn't aware that the new ones could be turned on without damage. Thanks to everyone that gave the right answer. I learned something new. I have been looking for a cheap 12 volt supply and now I have several at no cost. Thanks all, Roy.

Answer 3

It really depends on what you are trying to achieve??

I use a 500W PC Power Supply on my bench that has a mains on/off switch already on it. If you want a PSU for troubleshooting go buy a decent one that has one of these switches.

Each mainboard has a line of 'jumpers' on it for the PW_LED, Reset SW, etc... one of these is Power On/Off. You can just use a screw driver to short this PW_ON jumper to turn it on.

Roy C: There is nothing wrong with a PSU without load. A standard ATX Switchmode PSU is quite happy with no load. I've got a friend that leaves one on 24x7 that he uses to connect a cheap 12v fridge (keep Coke and his lunch cold in his office). The fridge goes home with him every night and the PSU stays on with no load. The PSU has lasted nearly 3 years with no problems.

Answer 4

http://www.pcpower.com/products/assets/S61EPS/S61EPS2.jpg
Please refer to the 24pin ATX connector (Motherboard power). Pin #16 w/ a green wire should be shorted to any adjacent pin w/ the black wire (pins 3, 5, 15 & 17). Fan of power supply should immediately spin. If you connect a case fan to one of the 4 pin molex, it should also spin.

Answer 5

nicely, maximum desktops enable shutdown and skill off from the applying. do merely that.l in need of that, you may plug the skill cord right into a skill strip with a skill change. The visual demonstrate unit and peripherals could be close off too. Use a strip with a surge protection and get yet another benefit.