[FredVN]

I left a 3-year-old Compaq desktop computer at my summer camp last fall. Apparently, the cold temperatures got to it. When I returned recently, it was completely dead. No pilot light, HDD spinup or fans. Checked power at outlet, replaced power cord and verified switch continuity. All OK.

I remember from years past that power supplies typically contain a “power good” circuit that totally shuts down the supply if any voltage is out-of-spec. Assumed stiff lube in a HDD might be stalling the motor and overloading the power supply. Disconnected power from all drives, removed PCI cards and disconnected all USB cables. Still dead.

I borrowed and installed 2 used power supplies both of which are believed (but not known for sure) to be good. Neither produced any change.

Thus I am assuming that the motherboard is bad and overloading the power supply. Before jumping to that conclusion (and probably junking the computer) I would like to verify the power supply is OK. Don’t have another computer to try it in.

Does anyone know pinouts on power supply connectors? I’m assuming a small load (say a 1K resistor on each supply) and shorting the power switch leads should make a good supply operate. Is that correct?

Thanks for any insight anyone can offer.

FredVN

[kiwiguy]

No, most power supplies need a few amps of load, not a few milliamps.

Pinouts are here though
http://pinouts.ru/Power/atxpower_pinout.shtml

[lwdarkwolf07]

This is a non lethal way to test ur power supply. unhook the main supply bundle of wires that supplies power to the Mobo. make sure ur power supply is unplugged. Take a paper clip and find the GREEN WIRE. Put one of the the paper clip into it and the other to the right or left of it. let go of the paper clip, plug in the supply and if ur supply turn on. your supply is ok, otherwise. Some things can be wrong. Power button not put in right, bad mobo, processor. one of the 3.

[Frank4d]

Originally Posted by lwdarkwolf07

Take a paper clip and find the GREEN WIRE. Put one of the the paper clip into it and the other to the right or left of it.

To clarify, jumper the green wire to one of the black wires. You can leave your case fans and drives connected which will provide the needed load.

My guess is if this PC has been sitting around un-powered for several months, and is already 3years old, the CMOS battery is dead. It is usually a CR2032 and is about the size of a US nickel. If you have a voltmeter you can check it. It should be about 3 volts.

[FredVN]

Thanks to all for the info. Checked the battery and it was dead, but replacement didn't change anything. Jumpering green and black leads got the power supply going with correct output voltages. Hence it appears the mother board or processor is bad.

Thanks for the help and education.