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Power supply or motherboard dead?

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Deathray2K

Member
A couple days ago, I was doing some work in VS when my computer just switched off. I tried to turn it back on and nothing happened. I tried moving it to another outlet, in case I'd overloaded a circuit (There were 3 computers plugged into it, the other 2 are just fine), but to no avail. Just to be clear, when I pressed the power switch, absolutely nothing happened. No fans started, there was no activity at all. By then I figured either the PSU or the motherboard were dead, and probably the PSU. However, I tested the power supply using Corsair's instructions:
You can easily test a power supply for functionality with a simple paperclip. First, disconnect all the cables from your motherboard and other devices, but leave the power supply plugged into the wall. Next, bend the paperclip until you have a U shape. Find the 24-pin ATX connector and plug one part of the paperclip into the socket where the green wire ends, and the other end into the socket where a black wire ends. Make sure the power switch on the back of the PSU is on, (should be the I symbol) and the fan should spin up. If it doesn’t, your power supply may be bad.
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and the fan did indeed spin up. Just in case, I also tried shorting the power switch to make sure that wasn't the problem.
Also, the light on the motherboard does come on while the power supply is turned on.

So, now I suspect the motherboard is most likely at fault, but I don't really trust that PSU test being very accurate, and I don't want to replace the motherboard only to find out it was just the power supply all along. So, what do you smart folks here think? PSU or mobo?

The motherboard is an Asus P8P67, the power supply a Corsair HX850. Neither is particularly cheap, so I'd like to avoid replacing both.

Edit:Correction, if I cycle the power supply and then hit the power switch, I get a moment of very slight movement in one case fan before it all goes dead.
 
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Myself i do think it's the PSU. if you have another one you should try it before. i never see a MOBO stop just like this.so it is a power failure.
 
There are other possibilities than either PSU or MB. Check the PSU with a multi meter. If PSU checks out, try a minimal install with just CPU, GPU and, one stick of ram.
 
Well, I just tried connecting it to a known good PSU, and I got a flashing standby LED... I tried to find out what that meant and what I found on Google is all over the map.
I tried a minimal install, same results.
 
Deathray2K said:
Well, I just tried connecting it to a known good PSU, and I got a flashing standby LED... I tried to find out what that meant and what I found on Google is all over the map.
I tried a minimal install, same results.
Click to expand...

You disconnected all drives and tried one stick of ram? Did you try another stick of ram all by itself? Did you make sure the one stick of ram was in the right slot for that configuration? If you don't have a multi-meter buy one. They're cheap and eliminate a lot of questions.
 
That's right, I tried a minimal install (1 dimm, cpu, gpu only) with 2 different sticks of ram installed in the recommended slot. No difference.
Sorry, I don't have a multi-meter available, nor would I know how to use one. I'll fix that later, but for now I just need to figure out what I'm RMAing.
 
Deathray2K said:
That's right, I tried a minimal install (1 dimm, cpu, gpu only) with 2 different sticks of ram installed in the recommended slot. No difference.
Sorry, I don't have a multi-meter available, nor would I know how to use one. I'll fix that later, but for now I just need to figure out what I'm RMAing.
Click to expand...

That's why I'm suggesting a multi-meter. They can be had for ~$20 and can tell you if it's the PSU (they come with destructions). Plus, multi-meters come in handy for a plethora of home projects.
 
I have no intention of RMAing blindly, I just hoped someone would have further insight into what the problem was.
I can get a multi-meter but I don't have any idea how to test a PSU with it, or how to interpret the results of that testing.
 
Deathray2K said:
I have no intention of RMAing blindly, I just hoped someone would have further insight into what the problem was.
I can get a multi-meter but I don't have any idea how to test a PSU with it, or how to interpret the results of that testing.
Click to expand...

Which is why I mentioned, "they come with instructions." No one can tell you to turn knob A a 1/4 turn to the left, reboot and, hold a taco over your left ear and you're good to go. You have an issue that could have many different causes.
 
Well, I have a multimeter around somewhere, but my point is that knowing how to use a multimeter is not the same thing as knowing how to use a multimeter for testing a PSU. The instructions that came with (Not that there's any chance I could find them) aren't really helpful for this particular problem. I wouldn't know what distinguishes a working PSU from a partially working PSU.
 
Deathray2K said:
Well, I have a multi-meter around somewhere, but my point is that knowing how to use a multi-meter is not the same thing as knowing how to use a multi-meter for testing a PSU. I wouldn't know what distinguishes a working PSU from a partially working PSU.
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You check the power outputs on the various lines for their listed ratings according to the label on the side of the PSU. If they are seriously off according to the ATX Power supply guide/definitions then, you know it's the PSU. If you are unwilling to try and learn how to do this then, by all means, rma it. I'm not trying to force you to do anything. I'm just trying to offer options.
 
I understand, and I do appreciate your help.
In any case, I decided to test the PSU in another computer and it worked, so I can eliminate that as the problem. I guess then that it's the motherboard. Unless you have some reason to think otherwise?
 
Deathray2K said:
I understand, and I do appreciate your help.
In any case, I decided to test the PSU in another computer and it worked, so I can eliminate that as the problem. I guess then that it's the motherboard. Unless you have some reason to think otherwise?
Click to expand...

It may be the CPU but, it's more likely the MB. It could be the GPU and it wouldn't hurt to try that in the other machine.
 
Deathray2K said:
I have no intention of RMAing blindly, I just hoped someone would have further insight into what the problem was.
I can get a multi-meter but I don't have any idea how to test a PSU with it, or how to interpret the results of that testing.
Click to expand...

Looks like you've already eliminated the PSU as the cause, but for future reference:
http://forums.anandtech.com/showthread.php?t=257485


I agree that there are several possible causes of the problem. You COULD just start RMA'ing things...but it makes more sense to try to troubleshoot the problem...and the cause before sending components off for replacement.

Do you have the option of testing the CPU in another computer?
 
Thanks for the link BoomerD, it's very helpful.
I can't test the CPU in another computer unfortunately, this is my only 1155 system.
I'll test the GPU as well, tomorrow. Right now I'm done for the night, after going through Asus's support system and being told to RMA, then finding the RMA form completely useless... I'll do some more testing tomorrow.

Is there any way to check if the cpu is the problem without another machine?
 
Deathray2K said:
Thanks for the link BoomerD, it's very helpful.
I can't test the CPU in another computer unfortunately, this is my only 1155 system.
I'll test the GPU as well, tomorrow. Right now I'm done for the night, after going through Asus's support system and being told to RMA, then finding the RMA form completely useless... I'll do some more testing tomorrow.

Is there any way to check if the cpu is the problem without another machine?
Click to expand...

Not really...unless you have a different 1155 motherboard to swap the current one with....
 
If the case fan moves just momentarily and shuts down it sounds like you have a short to ground and it's shutting the power supply down. Look for loose screws around or under the board or a place where something isn't lined up and shorting. To eliminate or confirm this, take the board out and run it in on a flat surface and see if it works or behaves the same way; you're going to have to take it out to RMA it anyway..
 
Yeah I tried that just now, still nothing. I've ordered a new motherboard (From a different manufacturer, I'm fed up with Asus), and I'm RMAing this one, then I'll sell it. Anyone interested in a P8P67? 😛
 
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