How to test a desktop computer power supply

Links for getting a power supply tester are on my website:
http://www.defcon-5.com/noc/video.cfm?docid=372

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.

Category:

Howto & Style

Tags:

• Power
• supply
• testing
• tester
• volt
• meter
• replace
• install
• voltage
• computer
• desktop
• how-to
• educational
• instruction

[elkwyre]

is it possible to test a PSU without a meter?

I have a psu that i haven't yet installed but have connected to the mains and the fan does not rotate...does this mean its shot?

[DefconComputers]

You would jumper the black and green wires, and then test it with a multi meter if you don't have a tester.

Other than that, no real way. The fan in general should move though, so that is a pretty good chance that it's bad.

[moranatang]

what PSU tester is that

[DefconComputers]

@moranatang It's an Apevia. I have a link to it on my site in the description

[Onebadmonkey2]

If the readings aren't exactly 5, 3.3 or 12v, is that a big deal? My 12v reading fluctuates from 12 to 11.9 and my -12 reads about 11.7ish. I'm having computer issues lately too. It cannot wakeup from sleep without a bsod, so I'm suspecting power supply.

[linfan854]

@c0rrupts3ct0r555 yet mine lasted 12 years.

[adyandrey23andrey]

tried the green+black wire on my Compaq PSU and didn't work....i get just a little spark in the 24 pin connector and...that's it.

[dandj3]

I love your videos. I have just started a computer information systems degree and your videos help me understand everything that I am reading in the book. I also have just been hired as a pc tech. Your videos help me on the job as well. Thank you for all your useful information.

[saren1994]

I tried to use the jump-thingy on the psu while its not connected to the mb. after i'd gone trough all the pins and check if the voltages is ok, it still didnt get my motherboard going.. it was like 0.1-0.2 volts deviation on some of the pins, does it have to be exactly what it says in the manual? now i dont know if the motherboard is gone or the psu after a lightning outside :s any tips what to do?

[c0rrupts3ct0r555]

omg, is that a maxtor hdd i see? do yourself a favor and smash it, maxtor is the worst hdd u can buy.

[tinymansd]

What is the reason for using the paper clip?

[drannard123]

thank you very helpful, I do as you said and I am checking voltages on pins but it has no voltage and the exhaust fan won`t work,,can you give me a possible cause of no voltage ..I have a power supply the same model in your video demonstration...thank please help me.

[drannard123]

thank you very helpful

[curemymind]

You should of used a power supply tester that isn't soo high tech. I got one off of hong kong from ebay thats a 24 pin which u can test the 20 pin, the sata the 8 pin and the 4 pin. The 6 pin and the floppy :| and all with leds with letters of what the voltage should be and the led only turns on when it reachs that. And it only costed me 5 dollars and thats inculding the shipping plus the wait but it was soo worth it. But a multi meeter is wroth the investment also.