Testing a power supply?

I don't see why you couldn't do that with a multimeter. Even if the motherboard power supply connecters are not connected, the power supply still sends power to the disk drives, so it probably sends voltage to all wires making it measurable by the multimeter even when not connected to the pc at all. Locate a manual (search the internet) that tells you what the voltage should be at each wire, with respect to the ground wire and measure it with the multimeter.

I agree, ATX power supply's supply power constantly to the main board, so the voltage should be present. Let me know if this works, thanks.

You would have to open the power supply case, you would need to know what points to check the +12 volts, +5 volts, - 12 volts, and -5 volts, and what range is acceptable.

A easier solution would be to purchase a Post-It Card that can check your entire system during Post, including if the correct voltage is beening provided by the power supply, clock cycles and etc.

Have you check that the fan is working in the power supply? If the fan is not working, it causes the power supply and CPU to heat up and cause incorrect voltages, causing problems, and will eventually burn up completely.

You can test it for voltage only, connnecting a multimeter set for current (AMPS) across a voltage source will either burn up the power supply or meter.
Consult a m/b manual for proper input voltages if I remember correctly there are only 3.

Yes, you can test the ATX power supply, but you have to complete the circuit of the power supply first. A quick a dirty home method, would be to connect the green (Power On #14)and black (Ground #13) connectors on the power supply with a paper clip. This closes the circuit. Now you can use the multimeter in the normal fashion.

(The black connector which you should use is

Maybe I should have made it a little more clear, I was wondering how to turn it on, which I got an answer for, but does anybody know which voltages go to which wires?
Sorry for the cofusion...

I did not include the color for the wires because I have found that some makers used different colors.

Pin 1 3.3v (optional)
Pin 2 3.3v (optional)
Pin 3 Ground
Pin 4 +5
Pin 5 Ground
Pin 6 +5
Pin 7 Ground
Pin 8 Power_Good (+5)
Pin9 5v_Standby
Pin 10 +12v
Pin 11 3.3v (optional)
Pin 12 -12v
Pin 13 Ground
Pin 14 Pwr_on
Pin 15 Ground
Pin 16 Ground
Pin 17 Ground
Pin 18 -5v
Pin 19 +5v
Pin 20 +5v

The plugs for the hard drives have 2 voltages.

Orange wires 12v
Red wires 5v

If you are trying to check this power supply unloaded your voltage measurements may not mean anything. Many Power supplies will work wonderfully on the bench but will cause flackey problems all the same once they are installed and under load. Also, using a Multimeter does not guarentee that the P.S. is good I have seen many power supplies look good on a multimeter but have a lot of AC ripple. You would need an Oscope to really check ripple. And finally, I would suggest that if you question a power supply and if looks good with a multimeter. I would still use a known good one to make sure that I eliminate the power supply as being the problem. Get yourself a good 400w P.S. to use as a tester. Its a small price to pay ( $60 to $80) but may save you a lot of headaches.

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