Windows 7 Desktop Computer Turns On and Off Again

Evga P55 desktop motherboard - intel chi...
February 12, 2012 at 19:03:18
Specs: Windows 7, core i5 750
So a few months ago I switched cases from midi one to a full tower. After the whole process I tried to start it up and when I did the fans started up for about half a second and then stopped. It repeats the process until I switch off power running to the PSU.

So I tested my PSU doing the old paper clip trick and that's okay.
Tested my CPU in another computer, tick.
Tested my motherboard too, check.

As a short term solution I switched to an older motherboard and continued with my upgrades. So now I have a new PSU and a new graphics card and still when I try my original motherboard it just starts and restarts over and over.

I realise the only thing I haven't changed is my RAM. Could faulty RAM do this to a computer and more exactly, do this to one computer and not another??

What else could be the problem? Thanks. (first time poster BTW)

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February 12, 2012 at 20:17:14
Did you reuse the same power supply or use one that came with a case?

Try the motherboard outside the case. If you switched cases you may have a metal standoff inserted where one should not be. You should have standoffs under every screw hole and ONLY under screw holes.

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February 12, 2012 at 21:21:18
Initially I used a PSU that came with my midi case but just yesterday I tried using my new one (AX 850) and still the same problem. When I did test it with my new power supply I had it outside the case on an anti-static mat.

If I did have a standoff where it shouldn't be, would that short be enough to permanently mess with the motherboard? Because it does work in other systems just not with my current hardware.

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February 12, 2012 at 21:34:37
"Because it does work in other systems just not with my current hardware".

What does work in other systems? The motherboard? If so, then that isn't the problem.

All you need to bench test a board are the following items: power supply,

Motherboard, CPU/HS/fan, 1 stick of RAM, Graphics card or onboard graphics, monitor, keyboard. Be sure you applied thermal paste to the CPU and connected the CPU fan to the header marked CPU fan. Also need to connect the auxiliary power connector to the motherboard in addition to the 20/24 pin main power connector. If you don't have onboard graphics and are using a graphics card that requires an additional power connector be sure to connect it too.

No other hardware, cards, drives, wiring, etc. To start the board momentarily short the two pins that are marked POWER.

If the board starts then you can install in case and retest with only the case to bard wiring added. Then if all is well you can add the drives and additional cards, if any. Do not add any external hardware other than monitor, keyboard and mouse until after Windows is fully installed.

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Related Solutions

February 13, 2012 at 04:16:09
Hi OtheHill,

any thoughts on the 'earthing' standoff being missing or incorrectly located/fixed?

Good Luck -Keep us posted.

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February 13, 2012 at 09:53:43
Could incompatible RAM cause this by any chance? Apart from that I'm not sure what else could be the problem. Everything works on it's own in another system but not together either on a bench or in a case.

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February 13, 2012 at 11:41:20
You have to start with the minimum and add one part at a time. Otherwise something is not compatible or connected wrong.

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February 13, 2012 at 15:12:38
Did you try bench testing as I described in #3 above.

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February 13, 2012 at 16:21:22
Yes I had done that already. Same result, i.e start, stop, start, stop. Thanks for giving me a hand by the way.

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February 13, 2012 at 19:33:30
"I realise the only thing I haven't changed is my RAM".

Does the above statement include removing the heatsink/fan from the CPU?

Then I would guess the CPU is overheating and shutting down. If you have time try to boot into the BIOS (setup) screens at start up. There should be a screen in there that shows the temperature of the CPU and the system.

There is also an option to select what temperature to shut down. It is possible that option is set lower than necessary.

Post any results you find. Clarify how long the computer stays running. Does it automatically restart or do you need to restart it? Can you restart immediately after it shuts down?

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February 14, 2012 at 03:26:04
Hi Souptard,

If I understand correctly, the mobo fails when installed in the full tower, but *WORKS OK* elsewhere or when free standing on a bench.

Have you used the new psu for this testing?

If so, suggest checking the standoffs.

a) generally one standoff is metal and used for earthing.
This standoff goes in the mobo earthing mounting hole.
The hole can be identified as it has a metal contact ring printed on the mobo.

b) could the new tower require longer standoffs?
e.g. if you are using the original (shorter) standoffs, could something on the mobo be touching the case.

Good Luck - Keep us posted.

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February 14, 2012 at 10:00:21
To clarify, You are not getting the board to run when outside the case either?

The difference may be the power supply then.

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February 17, 2012 at 11:25:54
No it doesn't work at all either in the case or out of it. I also got some brand new compatible RAM and tried it... still just starts for half a seconds then restarts and repeats until I switch the power off. All the fans run including the CPU fan for that second. Motherboard doesn't even get a chance to show a debug code on the onboard LED display. I've tested the new PSU again too and it works just fine.

Here are my specs: Intel core i5 750 - processor
EVGA P55 SLI - motherboard
AMD Radeon HD 6950 - graphics card
Corsair AX 850 - PSU
2x 4GB DDR3 KVR1333D3N9K2 - RAM

I'm gonna hand it into a shop and see what's wrong with it. That is unless anyone has any more ideas?

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February 17, 2012 at 13:51:19
Did you try running outside the case using ONLY the hardware described in #3 above. Don't connect ANY case wiring. Start the board by momentarily shorting the two start pins.

Verify you have BOTH the 24 pin main power connector and the auxiliary CPU power connector. If your graphics card requires addition power make sure those are also connected. Your CPU fan must be connected to the header marked CPU fan.

If nothing happens then remove the one stick of RAM, re-seat any add in graphics card, and try again. You should get audible error codes then.

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February 17, 2012 at 15:08:52
Yeah tried that and still same outcome.

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