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Bad PSU?

by jtrory / March 3, 2009 12:30 AM PST


I think my PSU has died, but I want to be more sure so I'm looking for a second opinion.

This morning, I tried powering on my computer and nothing happened. No lights, no fans spinning... nothing. For a while now, whenever I have turned my computer on, it's taken two or three tries to get it to fully power up (the lights and fans would come on for a split second, then die). I'm thinking this was my PSU telling me it was kicking the bucket.

Anyway, I have replaced the power cable, tested all the connections, and there doesn't appear to be a power light on the mobo, indicating I believe that the mobo is not receiving power.

The one curious thing is that when my computer is plugged in, but the PSU is turned off, my power strip's "grounded" light turns on. When the PSU is turned on again, it goes off. What does that mean? I don't remember if the grounded light is supposed to be on or off.

Another thing is that whilst there is no power light on the mobo, there is light coming from two LEDs on my Ethernet port, suggesting to me that there is some power coming from somewhere.

If anyone can help me confirm it's the PSU, I'd really appreciate it, or for any other ideas. Thanks.

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Those ethernet LEDs
by R. Proffitt Forum moderator / March 3, 2009 1:08 AM PST
In reply to: Bad PSU?

Are no sure sign so let's dismiss that.

The test for if its the PSU is to either measure the output with a Volt Meter or just switch it with a new good PSU.

"it's taken two or three tries to get it to fully power up (the lights and fans would come on for a split second, then die)."

This happens under a few conditions with a GOOD PSU. Here they are for you to research on google.

I don't write more since plenty written already.

2. An IDE cable off by row, pin, upside down or a dead hard disk.
To test this I unplug the IDE cables.

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Not bad caps or IDE cables
by jtrory / March 3, 2009 1:35 AM PST
In reply to: Those ethernet LEDs

Tried unplugging the IDE cables and still nothing, and the caps are fine. Where would I get a voltage tester from? Home Depot? And how do I use it on a PSU?

I'm thinking I should just get a new PSU from Newegg and see what happens. If it turns out it's not the PSU, Newegg will probably let me return the new one.

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Then treat it like THE DEAD PC.
by R. Proffitt Forum moderator / March 5, 2009 5:38 AM PST echoes what I do next. I pull out the motherboard, CPU+HSF, the PSU and the speaker.

Now with just those 4 parts I can test for a power up. If no power up then I'm looking at the 4 bad or horribly misconfigured parts.

-> In closing some boards do not power up if the CMOS battery is dead. Use a Voltmeter.
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If you have the motherboard, etc...
by R. Proffitt Forum moderator / March 5, 2009 6:34 AM PST

Out of the case and it won't power up, the POWER ON switch can be broken. We use a pen tip or something else to give it the ON signal.

We also check that CMOS BATTERY and the CMOS CLEAR jumper. That's a reason I come across weekly.

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Tried the pen thing
by jtrory / March 5, 2009 6:42 AM PST

Bob, I tried jumping the power switch on the mobo with a screwdriver but it did nothing. The only thing I'm wondering now is if it's the CMOS battery. Even though the mobo is fairly new, and I've never had to change a CMOS battery before, it's one of the only things I haven't tried and is worth a shot.

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Not the CMOS either
by jtrory / March 5, 2009 8:43 AM PST
In reply to: Tried the pen thing

I changed the battery and it did nothing. I'm sending the PSU back to Newegg for a replacement, because I'm still pretty sure it's the power supply. My only concern is that if it's not, I've really got no way of testing the other parts without buying more, and I can't keep buying and returning things from Newegg.

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There is a PSU test worth knowing about.
by R. Proffitt Forum moderator / March 5, 2009 8:53 AM PST
In reply to: Not the CMOS either
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practically anyplace that sells power supplies
by ramarc / March 3, 2009 1:14 AM PST
In reply to: Bad PSU?

will test it for you for free. (a simple tester is about $15.)

as for your LEDs on your mobo and ethernet port, PCs use multiple rails... 3.3v, 5v, and 12v. i can't remember exactly but i think the CPU uses 3.3v and 12v power while most other mobo components use 5v. a power supply's 12v or 5v output can 'die' while the other rails will still be functioning.

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Still nothing
by jtrory / March 5, 2009 4:51 AM PST

Bought a new PSU and my computer still will not power on. I tried checking the connection of the power button itself, but it's hard to tell - I can't see it very well. Also, my old PSU had a separate power cable for the fan, that plugged into the mobo. Odd? I think the fan power is supplied by the 24+4 cable, but I'm not sure...

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dying power supplies are vengeful
by ramarc / March 5, 2009 6:03 AM PST
In reply to: Still nothing

they can often take a mobo or other components to the graveyard with them. the only power supply to die on me took my mobo, a video card, and a hard drive along for the ride. Sad

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All gone
by jtrory / March 5, 2009 6:24 AM PST

I stripped everything down to the mobo, and still nothing with either PSU. Does that mean then that it could be the mobo? It's barely two years old! What about checking the CMOS battery, could that do it?

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