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How to test a desktop computer power supply





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Uploaded on Sep 22, 2009

Links for getting a power supply tester are on my website:

There are several ways in which you can test a desktop computer power supply. My perfered method is to use a power supply tester. This is because it's much faster, simpler, and there is less risk of having a component burn out or getting a nasty shock yourself. You of course can test a power supply using a volt meter as well. A volt meter will give you more information about the power supply, but in most cases is not needed. The only time I use a volt meter is when I suspect the issue could be the power supply even when my power supply tester shows that everything is fine.

With a power supply tester all you have to do is connect the main power connector and the processor connector from the power supply to the tester. Then apply power to the power supply and you will get a reading of each voltage.

When using a volt meter you will need to jumper the green wire to one of the black wires using a small piece of wire. Once that is done you can apply power to the power supply and begin testing each colored lead. Be sure sure to document each voltage, and then review them when complete for identifying issues.

In general any voltage more than 5% off in either the positive or negative is an indicator of a bad power supply. You should be expecting voltages of +3.3, -12, 12, -5, and +5 if you are getting numbers outside of the 5% margin on those then that confirms the power supply is bad. I personally hold power supplies closer to 4% as at 5% you will have issues and I expect small drops to happen with power distribution.


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