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can i test a ATX2.2 p/s by shorting the power pin?

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October 10, 2007 5:39:36 AM

Hi there, hopefully this is a nice simple question. I've always tested my old power supplies by shorting out the soft-power pin to a ground pin and then (briefly) turning on the p/s to see if the fan spins up. On a 20-pin ATX plug, the power pin is 14, and I would connect it to pin 15 with a bit of wire or a paperclip.

Well, I just bought a new ATX 2.2 p/s, with the 24 pin ATX plug and the separate 4 pin 12v plug. My question is, does the same trick still work? Counting the 4 extra pins on the 2x12 ATX plug, the soft power pin is now 16, and the pins next to it are both grounds - so can I short those the same way, and expect the p/s to turn on? Or is there some kind of new-fangled safety that makes this trick not work?

Your help greatly appreciated. If this trick still works, then I guess I have a brand new dead power supply. If anyone is curious, it is an Antec 430W "Earthwatts" model EA-430. Thanks!

Adam
October 10, 2007 6:14:27 AM

The "PWR ON" wire should be the green one. I believe that the PSU needs a minimal draw on the 5V in order to turn on. I can't remember .5-1A or something like that. The PSU is probably OK. I'm not sure about this, but I don't think it's a good idea to run a switching PSU in a no load condition. Maybe someone else has some input on that.
October 10, 2007 6:50:22 AM

Thanks Zorg. Is that new? On all my old power supplies, if you short that green wire to ground you can at least see the fan spin up and verify that the p/s is partially functional.

So, if that trick doesn't work, what's a good way to test this thing? Because if this p/s is good, then I've gotten two DOA mobos in a row, which seems unlikely. I'd like to verify that it's good before I go any further but I'm not sure how to these days.
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October 10, 2007 7:31:35 AM

Hmm... would a ATX2.0 tester work on an ATX2.2 p/s? Because the "short the power pin" test works fine on an ATX 2.0 (I just tried it).
October 10, 2007 8:12:04 AM

adam_w said:
Hmm... would a ATX2.0 tester work on an ATX2.2 p/s? Because the "short the power pin" test works fine on an ATX 2.0 (I just tried it).
Well it says 20 and 24 pin, I haven't used them but I'm sure they work.
Quote:
Antec Power Supply Tester

ATX power supply tester: Test your PC's power supply to make sure it's working correctly. The green LED lets you know that it's normal, while yellow is for insufficient and red is for over-voltage conditions. It’s a must-have to ensure that your system is properly powered.

Easy to use: No need to fuss with voltmeters or probes. Simply plug the power supply outlets into the 24-pin or 20-pin connector to verify the voltage of each ATX12V rail.

Power good signal: A separate signal tells you whether your power supply is working or not. It’s a quick and easy way to see if your power supply is adequate—saving you time and trouble.

October 10, 2007 8:13:19 AM

How sure are you that your case power on switch works. Try shorting the motherboard power on switch pins momentarly and see it the supply turns on. Do not try the green wire short with it plugged into the system because it stops the overcurrent circuit in many supplies from turning the thing off. This will of course cause the blue smoke to escape which allows all computers to work. Once the blue smoke gets out you are in real trouble.

:) 
October 10, 2007 8:18:32 AM

Quote:
Power good signal: A separate signal tells you whether your power supply is working or not. It’s a quick and easy way to see if your power supply is adequate—saving you time and trouble.


I spent a little more and have one with a LCD display that shows the actual voltage values and how long it takes power good to come up. Interestingly enough I have replaced several supplies where the power good signal took to long to come up causing the system not to turn on. The all LED testers generally do not seem to find this problem.
October 10, 2007 4:44:39 PM

Azimuth, I've tried shorting the power header to verify that the case power switch wasn't the issue. And the shorting the ATX pins thing is nothing I would do anywhere near the motherboard, it's just something I've done in the past as a last test before throwing the psu away. The process I followed is:

1. Take the psu out of the case, unplugged from everything, sitting on the floor
2. Stick a bit of wire so it's connecting the green soft power pin to one of the grounds next to it
3. Plug the psu into the wall, turn on the hard power switch for a second, then turn it off and unplug it.

On every other (non-dead) psu I've tried, that makes the fan spin up; on this one, nothing happens. I know I should probably get a psu tester, but I'm loathe to, because by the next time I need it, we'll probably be on ATX 2.7 and the plug will have 28 pins :) 
October 11, 2007 5:46:09 AM

Hey, thanks for all the advice guys, it was indeed a bad psu. Replacement is in place and it's formattin away.
October 11, 2007 6:30:56 AM

Happy to hear that the tester worked, and that all is well.
!