Bright spark needed?

Question

If i remove a PSU from an old PC Tower. Plug it in, not connected to anything else, throw the switch, should the fan start up, or does it have to be connected to the mobo HD etc. I'm just trying to find out if its working or not

Answer 1

sewrobb is wrong, unless he means only the old AT power supplies.

An atx PSU will not start unless the power on pin 14 (normally green) is shorted with any ground pin (usually black). This happens when you plug it into the motherboard. You can use a piece of wire, paper clip or similar to short these two pins and plug in and switch on the power supply to see if it is working.

Do this at your own risk. Check your particular supply for accurate information on the power on and ground pins.

The link below shows how to short the pins for testing.

Answer 2

I believe it needs to be connected to a motherboard as it requires a feedback signal (power good) to maintain output.

Without the powergood signal it fails to start fully.

However it may just be dead.

Answer 3

Oh Your Pic is my Hero!!!!!

Answer 4

Depends on the type of power supply.  In the old days of AT the power supply was totally independent of motherboard control and the switch on the front of the case directly controlled the power supply. In this case the power supply could be tested totally independently of the motherboard or any other equipment.

If it is an ATX power supply - as is most likely the case - then the power supply needs to be connected to the motherboard.  If the motherboard does is faulty then that could make the power supply appear to be faulty as well.  Also, the power supply is turned on by a switch connected to the motherboard.  If the wire that connects that switch on the front of the case with the connector on the motherboard has fallen off then the power supply won't turn on.  The fan could also fail inside the power supply.

I would say the best way to test is to try the power supply with a computer that otherwise works fine. If you test the power supply with a computer you know works then you can totally rule-out the power supply.  

Answer 5

Needs to be connected to a motherboard, but if you want to power the PSU without connecting it it can be done, look at the following page for instructions...

http://www.overclock.net/faqs/96712-how-...

Answer 6

It will start running but it depends if there's a processor or not. If there isnt it will start running even before you throw the switch. So i advise you to test it with a working processor in it.

Hope you're answered.

Answer 7

No it doesn't need to be connected. When you switch it on whether it's supplying power or not the fan should start. The fan runs on the same circuit as the output. If you switch it on and the fan's not working the unit is dead. Either the imput or the output has blown. If your replacing it they are around about £40 to £50 depending on the rating and where you get it from.