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computer turns off and on?


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#1
xonic

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I just built a new computer for someone and when I turn it on, it just turns off and turns back on again over and over. I've tried 3 different power supplies and it still does it. I'm kind of stuck now I'm really not sure what it is. I'm guessing it's either the motherboard or CPU.

Motherboard: Asus P7H55-M Pro
CPU: Intel i3-530 Dual Core 2.93Ghz
RAM: Crucial 4GB
PSU: Antec NeoPower 550W (ATX 12V + EPS 12V)
HD: Seagate 1TB


Thanks in advance

Edited by xonic, 30 July 2010 - 09:41 PM.

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#2
phillpower2

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HI xonic Welcome to GTG
Have a look at this checklist & see if it helps;
http://www.tomshardw...61145_13_0.html
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#3
xonic

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HI xonic Welcome to GTG
Have a look at this checklist & see if it helps;
http://www.tomshardw...61145_13_0.html


The 2nd step says I must plug in the 4/8 pin connector, but should I have the bigger one plugged into the motherboard as well? When I did this the computer just restarted itself over and over pretty much. It doesn't turn on if I only have the 4/8 pin connector in. I've never had this problem before and I've built at least 6 computers. :)

Thanks.
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#4
phillpower2

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You should only plug in either the 4 or 8 pin plug for the cpu and
the main power plug, this has either 20 or 24 pins, is it when you
connect the main power plug that the computer keeps on restarting?
This could suggest a short circuit or the reset connector on the
front panel header in the wrong orientation (wrong pins).
Try a barebone setup outside of the case if your connections are
all in the correct position then if you have used standoffs make
sure they are in the correct locations.
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#5
xonic

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You should only plug in either the 4 or 8 pin plug for the cpu and
the main power plug, this has either 20 or 24 pins, is it when you
connect the main power plug that the computer keeps on restarting?
This could suggest a short circuit or the reset connector on the
front panel header in the wrong orientation (wrong pins).
Try a barebone setup outside of the case if your connections are
all in the correct position then if you have used standoffs make
sure they are in the correct locations.


When I had both the 24 pin and 4 pin connected, it would just turn off and on.
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#6
phillpower2

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I would remove and set up the board outside of the case,
inspect the main power connector from the psu and the
socket on the MB it plugs into, if they look in good order
only connect the basics, gfx, HDD, 1 stick of ram, keyboard,
if it doesn`t start and then restart itself, I would then
use a small screwdriver to short the 2 pins that switch on
the computer via the MB switch header , if it boots up ok
you should check the power on + reset switches on the case +
if you used standoffs that they are in the correct locations.
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#7
xonic

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I would remove and set up the board outside of the case,
inspect the main power connector from the psu and the
socket on the MB it plugs into, if they look in good order
only connect the basics, gfx, HDD, 1 stick of ram, keyboard,
if it doesn`t start and then restart itself, I would then
use a small screwdriver to short the 2 pins that switch on
the computer via the MB switch header , if it boots up ok
you should check the power on + reset switches on the case +
if you used standoffs that they are in the correct locations.


I noticed that one of the gold metal pieces inside the 24pin connector coming from the PSU is missing, could this be the reason?

edit: nvm, I guess that's just how they are
edit2: with the mobo out of the case with both power connectors in, 1 stick of ram it does not restart itself. testing more in a bit

Edited by xonic, 29 July 2010 - 12:14 PM.

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#8
xonic

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update: I did get a signal from the monitor but when I put everything else in, it just shuts off and turns back on. when I dont have my HD plugged into the PSU it stays on.

I guess it's my power supply?
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#9
phillpower2

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I noticed that one of the gold metal pieces inside the 24pin connector coming from the PSU is missing, could this be the reason?

Possibly, I have never encountered this type of problem but maybe someone else on the forum has and could advise, has it damaged the contacts in the MB socket?

update: I did get a signal from the monitor but when I put everything else in, it just shuts off and turns back on.

when I dont have my HD plugged into the PSU it stays on.

To clarify for us, it only does it when the HDD is connected to the setup, is that correct.

I guess it's my power supply?

Or the HDD PCB!

Can you loan another psu to try and get yours tested! same goes for the HDD.

EDIT: PCB = Printed circuit board

Edited by phillpower2, 31 July 2010 - 03:35 AM.

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#10
xonic

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Alright, I tried another PSU and it does the same thing. If I have both of the powercords connected (4pin and 24pin) it keeps restarting, but if I only have the 24pin in, it doesn't. But I do need both in, correct? The picture that was in the first link you posted confused me a bit about them.

Also, it says "Did you install the standoffs under the motherboard? Did you place them so they all align with the screw holes in the motherboard, with no extra standoffs touching the board in the wrong place? A standoff installed in the wrong place can cause a short and prevent the system from booting."

Does this mean if there's no screw in the standoff this can happen? does it mean a standoff in the case, but not touching the motherboard can cause this?

Edited by xonic, 29 July 2010 - 04:59 PM.

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#11
xonic

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I've tried 3 different power supplies and it still does it. Even with the CD drive in, so it's not the HD. So I'm down to the motherboard or CPU I guess?
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#12
phillpower2

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Does this mean if there's no screw in the standoff this can happen? does it mean a standoff in the case, but not touching the motherboard can cause this?

Yes!
I should have asked this earlier but is the MB under warranty?
If it is & you are happy you have checked everything is as it
should be I would return it, I could be wrong but I doubt a bad
cpu would cause this issue & more likely to be a bad board which
could include a short circuit.

Edited by phillpower2, 31 July 2010 - 03:49 AM.

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#13
xonic

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Manufacturer Warranty
Parts 3 years limited
Labor 3 years limited

so you think it's the motherboard
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#14
phillpower2

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It is looking like the MB is bad but a couple more things I would check before returning the board;
follow the canned text of Digerati to double check the PSU, if only to be certain you have done as much testing as you can,

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronic repair facilities.

Fortunately, there are other options that are almost as good. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

Swapping in a known good supply is a tried and trued method of troubleshooting, used for years even by pros. If you have access to a suitably sized, spare power supply, carefully remove the suspect supply and replace it with a known good one and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

Note the required voltage tolerance ranges:

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply.

Other than the above the only other suggestion I could make would be to remove & inspect the CPU & socket (bent or missing pins), after that I can`t think of anything we havn`t checked.
Thanks to Digerati for the psu test procedures
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