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What is the procedure for testing Power Supply with Voltmeter?

Rockula
Rockula asked
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Last Modified: 2013-12-11
I have an Antec 380W Power Supply that I think is dead. I have an Apple computer that had a dead power supply, and Apple provide's info on exactly what to touch what to, and I was able to determine that the power supply is dead. But on this Antec power supply, I'm not sure what is what, where to touch, etc. I don't have electronic knowledge, so when Apple said what to touch, like say "1 with red, and 6 with black and you should get a reading of XXX, if so, then proceed to the next step, if not, then replace the power supply...", it was very easy. I didn't have to be an electrician to figure out if it was dead or not.

To check say the 3.3VDC power, I'm assuming you touch the red probe to one of the three that I think are on my PS. But then where do I touch the ground? To any of the COM points? Or does it have to be a certain one for each voltage I'm trying to measure?

Another thing that is confusing, on this site:
http://www.smpspowersupply.com/connectors-pinouts.html
Is that it shows a typical 20-pin connector, but my wires don't totally match their wires. My wires are exactly reversed. My wiring is just like theirs, only my pin is upside and backwards from theirs. In the end, 11 is 11, and 6 is 6, etc.. but not in the exact same positions as their diagram. So, I guess that really doesn't matter.

I guess I need to know how to check my pins, and if I can touch any of the three 3.3V points, along with ANY COM ground to get a reading, or does it have to be a certain ground. Same for the 12V and the 5.5V. And there are several 5.5V points. Which one do I touch?

Thanks!

jason
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Gary CaseRetired
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... by the way, the easiest way to test your PSU (and better than a multimeter, because it puts some load on the PSU, which is a more reliable test) is to get one of these very-handy-to-have gadgets:
http://www.newegg.com/Product/Product.aspx?Item=N82E16899887004

Author

Commented:
Boy... how silly of me to miss. It says "Pin Side View". So yeah, when looking at the pin holes, and not from the top where the wires go in, it does match.

I'll look into the PSU gadgets. I need to make me a Newegg order anyway.

So, if I touch the red 3.3 and black to ground, and get nothing, and the same for any of the 5.5v or the 12v postives to ground, and get nothing, then that sucker is probl dead right? I don't see how it couldn't be.

Now whether my mobo is toast or not, is another question all together I guess. Because I've not researched if there is a way to tell if it's smoked or not.

I'll report back.

j

Author

Commented:
Oh, one more thing. The PS has to be plugged into the Mobo when I test it right? my Apple one was. But I think if I plug the PS into the wall, I connect it to the Mobo, as well as connecting the CPU terminal from the PS too right? Or can I leave it off? I guess it doesn't matter. If power is flowing thru it, than it would indicate it was good. But somewhere I read something about having to terminate the CPU power connection with a screwdriver or something. I just can't remember the context.

Thanks!
Jason
Gary CaseRetired
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Commented:
The power supply DOES have to be ON to test it :-)

... and that doesn't just mean plugged in.   You can force it on (without connecting it to the motherboard at all) by shorting pins 16 and 17  (actually 16 and any ground) => i.e. the green wire with any black wire.   They have to stay shorted -- this isn't like the motherboard's "soft power" switch where you just apply a momentary short.

Author

Commented:
Can you please give me an example of how to short the connections? I knew it had to be on, but I didn't know for sure if it had to be connected to the mobo before plugging it into the wall and turning it on.

Thanks!
Jason
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Commented:
Be SURE you're shorting the correct connections !!

You can completely disconnect the power supply; then short pins 16 and 17 => that just means to electrically connect them together.   You can use a paper clip;  another wire; etc.    After you're got them shorted, plug the power supply in to the wall and it will turn on (if it's working at all).

Commented:
Ah... so pins 16 and 17 are the ones. Not some little dongle that connects to the mobo from the front of the case. That is the soft power switch you were talking about, and not to be confused here. I gotcha.

It's weird cuz I plugged the power cable into the back of the PSU, and the computer started to run. I wasn't ready for that, so I flipped the off switch on the back of the PSU and it never turned on again.

This PSU came with this Antec Sonata Piano Black Case, and I bought two of them at the same time. One fried out after about a year and a half, and this one just went, which makes it about three years old.

I'll let you know what I find out!

Jason

Commented:
PSU has to be dead. I just tested it and got nothing. Now if only I knew if the mobo was cooked or not? I'm not sure there is a way to tell, other than good old fashioned hooking it up to see huh?

Thanks!
Jason
Gary CaseRetired
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Commented:
Yes, the "... good old fashioned hooking it up to see ..." is about it :-)

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