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Troubleshooting a Power Supply

Last response: in Components
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May 18, 2010 8:27:05 PM

I had a PSU croak on one of my PC's at home. It's not under warranty, and before I spend the money I just want to make sure that there's nothing I can do about it. It simply won't turn on; I ground the green wire through a resistor, and plug it in, but the fan won't turn on, and I get no power on the 3.3v, 5v, or 12v rails.

What are some things that I should check before just spending the money on a new one? The capacitors are all fine, and there's no obvious damage to the PCB or any components. Just wondering if I'm overlooking something simple here.

Thanks,


- Jesse

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a b ) Power supply
May 18, 2010 8:37:51 PM

It looks as though you have already performed the basic test which is to insert a link between the pin with the green wire and the neighbouring pin with the black wire going to it. It is strongly recommended that you have some load on the PSU before turning it on to prevent damage. You have done this already by using a resistor, however a system fan plugged into a 4-pin molex connector would also be suitable.

If your PSU doesn't start at all when you power on then unfortunately it's dead and needs replacing. There's not usually much you can do to replace them. If you're unsure of the wattage you require then post back with your full system specs and we will be happy to offer advice on a quality PSU for your needs.
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May 18, 2010 8:47:38 PM

moody89 said:
It looks as though you have already performed the basic test which is to insert a link between the pin with the green wire and the neighbouring pin with the black wire going to it. It is strongly recommended that you have some load on the PSU before turning it on to prevent damage. You have done this already by using a resistor, however a system fan plugged into a 4-pin molex connector would also be suitable.

If your PSU doesn't start at all when you power on then unfortunately it's dead and needs replacing. There's not usually much you can do to replace them. If you're unsure of the wattage you require then post back with your full system specs and we will be happy to offer advice on a quality PSU for your needs.


Alright, I was afraid that was the case. Money's just a bit tight, so I was making sure I absolutely have to spend the money before spending it. I make my own PC's, so I can handle picking out a new PSU; thanks for the offer however. :)  I was mainly just trying to learn how to troubleshoot, if there were any further methods other than what I used.

Thanks,


- Jesse
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a b ) Power supply
May 18, 2010 8:54:49 PM

I can't think of anything else off the top of my head - usually the 'jump start' test is the bare minimum since this tests under extremely low load conditions so if it fails this it pretty much guarantees you have a dead PSU. If you're buying new then Corsair, Seasonic & the newer Antec models are recommended. Best of luck!
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May 18, 2010 8:56:59 PM

moody89 said:
I can't think of anything else off the top of my head - usually the 'jump start' test is the bare minimum since this tests under extremely low load conditions so if it fails this it pretty much guarantees you have a dead PSU. If you're buying new then Corsair, Seasonic & the newer Antec models are recommended. Best of luck!


Thanks :)  How are the Silverstone supplies these days? Jw :p 
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a b ) Power supply
May 18, 2010 9:05:48 PM

Silverstone are often hard to recommend since they often differ in build quality depending on the model and hence the OEM manufacturer. They have been known to be made by FSP, Enhance Electronics and Seventeam Electronics. Some models are better than others.

jonnyguru.com and hardwaresecrets.com are the places to look for competent reviews.
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May 18, 2010 9:06:28 PM

moody89 said:
Silverstone are often hard to recommend since they often differ in build quality depending on the model and hence the OEM manufacturer. They have been known to be made by FSP, Enhance Electronics and Seventeam Electronics. Some models are better than others.

jonnyguru.com and hardwaresecrets.com are the places to look for competent reviews.


Thanks, I'll check those sites out. It's been awhile since I've been in the market for hardware, and things seem to be quite different than they were 3 years ago. :D 
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a b ) Power supply
May 18, 2010 9:10:43 PM

Thats the downside to being involved in arguably the fastest growing technology in the world ;) 
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a c 144 ) Power supply
May 19, 2010 5:16:07 PM

Use a digital multimeter and check the PSU.

Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
You do not want to use a resistor here. You want to directly short the green wire to ground. It's a control lead. Open, it is floating at 5 volts. Shorted to ground, only a few milliamps flow through it.

http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. You can carefully probe the pins from the back of the main power connector.
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May 19, 2010 7:13:52 PM

jsc said:
Use a digital multimeter and check the PSU.

Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
You do not want to use a resistor here. You want to directly short the green wire to ground. It's a control lead. Open, it is floating at 5 volts. Shorted to ground, only a few milliamps flow through it.

http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. You can carefully probe the pins from the back of the main power connector.


I also attempted the test using a paperclip. My DMM had no reading on any of the rails. It's dead as far as I'm concerned. Thank you very much for your input :) 
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May 21, 2010 4:43:25 AM

Best answer selected by Pyroflea.
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