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Testing a power supply

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battmain

Instructor
Oct 11, 2002
67
US
Trying to help out a friend with a bad pc. It has no power. A new power supply fizzled a few seconds after installing it, so suspecting a bad motherboard.

Is there a way to test the power supply with a multimeter without hooking it up to the motherboard?
 
You can pickup a PS tester at a local PC Shop for about $15
 
Yep, multimeter, PS tester, or tongue, they can all tell you if you have power coming from the PS... but the PS tester might be the best bet :)

CJ

Don't drink and post, save that for driving home!
 
Ok, thanks. I see CompUseless has a test for 20 bucks. I'll get one from there.

CharlieJax, come on down and I'll use yer' tongue to test it with. lol! :) (Memories of testing a nine volt as a kid!)
 
yeah there are 4 core voltages.

How do I test a power supply while it is out of the case?

Answer: That depends on what you mean by test. No matter what, the power supply will not run without a load. PC Power and Cooling makes an ATX Power-Tester that supplies a load to one 5V line and then lights an LED if the power_good signal trips. This basically tells you whether the supply is dead or not.

To test the power supply thoroughly, you'd want to load all of the 3.3V, 5V, 5VSB (standby) and 12V lines to the maximum ratings specified by the power supply manufacturer. If you look back in the 6th edition of my book (you'll find the 6th edition PDF file on the 12th ed. CDROM) on page 357 you'll find information on how to construct power supply loads using common automotive bulbs or heavy duty wirewound resistors.
 
Just to test if there's power from a power supply, I usually short the green and black wires from the atx power supply. The green and black wires are side by side in the middle of the connector. If the fan turns, then the power supply is supplying juice but no guarantee that seperate voltages are ok or even if it's able to support a constant load. Shorting the wrong wires can be dangerous to your health...

anthony
 
Richyd,
What book?



Update. I got a tester and both power supplies are good. So I get to keep the good power supply as a spare. The motherboard is bad. I used an old motherboard I had sitting around and was told the hard drive had Win 2000 on it. It turns out the drive had Win Xp and it bombed on the new board which had a different type of video card. There isn't an available slot for the old video card, so he's trying to find his Winxp CD to finish the process. We might have this thing going soon.
 
Sorry that was an article i copied from another website but I forgot to edit the response.
Rich
 
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