how do I test an atx power supply?

March 20, 2011 at 18:42:24
Specs: Windows Vista, p4/2g
I have a pc that is not even trying to boot up. I see a green light on the MB, but no responce when I press the power button. I think the button's ok, so I need to test the Power Supply. I only have a Volt Meter.

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March 20, 2011 at 19:59:58
The lpower supply gives several voltages +/-12, +/-5, +3.3, +5sb. The green LED means the +5SB is working. It is present when ever the cord is on, +12, and +5 is at the drive connectors. The rest at the main power connector, It is common to have the 5vsb on and the rest of the power supply dead.

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March 20, 2011 at 21:58:46
Thanks! I have a problem with the PS.

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March 21, 2011 at 09:43:24
To test the PSU, unplug the main ATX plug from the board, bend a paper clip (or piece of wire) into a U-shape, put one end in the pin to the green wire & the other end to any black wire. This will bypass the power switch on the case & allow the PSU to power up as soon as it's plugged in or switched on. You can then test the voltages with your multimeter. Yellow = +12v, Red = +5v, Orange = +3.3v. The tolerance is 5% plus or minus.

However, amperage is what's important & there's no easy way to check for it. For example, just because your +12v may test within spec, it doesn't mean that it can supply +12v at say, 15A. The equipment for load testing costs 1000's of dollars.

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