# PC turns on for split second then turns off, repeatedly.



## ta2 (Nov 1, 2009)

Recently transferred my components to a new case. Changed the power supply, graphics card, sound card and hard drives.

The problem is that when I turn on the computer, all the fans start up and everything for about a second, then it turns off. I fixed this by taking the battery out and flicking the CMOS clear switch and putting the battery back in. It then comes up "press F1 for setup / F2 for defaults". Everything works good now.

The problem is that when I take the power cable out, or flick the PSU power switch, this whole scenario repeats itself and I have to do a CMOS clear to fix it. I have put in 2 different batteries, though I cannot be 100% certain that they are charged, I bet that's not the problem.

No idea what the cause is. Any help is very much appreciated.

Thanks!


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## Tyree (May 10, 2009)

PC Specs?
Prebuilt- Brand name & Model Number?
Custom Build- Brand & Model of Mobo-CPU-RAM-Graphics-PSU.


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## ta2 (Nov 1, 2009)

Custom Build

ASUS P5E
Intel E7200
Corsair XMS 4x1GB
XFX 8400GT
Corsair 400W


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## Tyree (May 10, 2009)

Are you sure the Mobo is not shorting to the case?


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## ta2 (Nov 1, 2009)

Tyree said:


> Are you sure the Mobo is not shorting to the case?


 Nope, how would I check that?


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## Tyree (May 10, 2009)

Remove the Mobo to be sure there are standoffs under ALL of the Mobo mounting holes. 
Best solution for testing:

Remove EVERYTHING from the case
Set the motherboard on a non conductive surface. The motherboard box is perfect for this. DO NOT PLACE THE MOTHERBOARD ON THE STATIC BAG! It can actually conduct electricity! We are going to try and assemble a running system outside of the case.
Install the CPU and heat sink.
Install 1 stick of RAM.
Install the video card and attach the power supply connection(s) to the card if your card needs it.
Connect the monitor to the video card.
Connect the power supply to the motherboard with both the 24pin main ATX Power connection and the separate 4 or 8 pin power connection.
Connect power to the power supply.
Do NOT connect ANYTHING else. Make sure you have the power connector on the CPU fan connected.
Use a small screwdriver to momentarily short the power switch connector on the motherboard. Consult your motherboard manual to find which two pins connect to your case's power switch. Then touch both pins with a screwdriver to complete the circuit and boot the system.

If all is well, it should power up and you should get a display. Then assemble the parts into the case and try again. If the system now fails to boot, you have a short in the case and need to recheck your motherboard standoffs.

If the system does not boot after this process, then you most likely have a faulty component. You'll need to swap parts, start with the power supply, until you determine what is defective


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## Rob_Rocker (Mar 15, 2010)

Just experienced the same problem. Found this thread and tried out the obvious. Took out the 250 GTS video card, rebooted the same issue. Swapped out the PSU. Still the same issue. Swapped out memory one stick at a time, same issue. Reset the CMOS. That did the trick. 

Not sure what happened to cause the split second on/off repeatedly during startup issue. BIOS settings were saved so that's a plus. So before sending back a MOBO reset the CMOS first. I was sweating having to buy the same MOBO (so the architecture would stay the same and I would not have to reformat the harddrive) or getting a new CPU.

So the first thing to try out: is resetting the CMOS that's the easiest and least expensive, then take out the RAM one stick at a time and reboot after each removal (to check if maybe one of the sticks of RAM has a bad module) Then if these haven't worked remove the Video card and finally the PSU before thinking it's the MOBO or CPU.

If anyone has an idea on what the BIOS may not like that would create a problem that requires the CMOS to be reset please let me know. All I was doing was changing out the CAT5 cable before this happened, because I was having problem with my internet connection. I never opened up my box, so static electricity coudn't have been the culprit.

Thanks,
Rob_Rocker (PC newbie)ray:

Ta2, repost on what you found the problem to be. Hopefully the thread will help some other poor soul...BTW my MOBO is also an ASUS P5E


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## ta2 (Nov 1, 2009)

Resetting the CMOS fixes it... *BUT* every time I take the power out (remove mains lead or switch PSU to off position) then it screws up again.


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## Tyree (May 10, 2009)

@ Rob_Rocker. Was the power cord unplugged from the PSU while changing cables? If not, that could have cause the problem you experienced.


@ta2
Did you do the bench test?
Why are removing mains leads or switching PSU to the off position?


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## linderman (May 20, 2005)

replace the CMOS battery


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## ta2 (Nov 1, 2009)

I would be turning off the PSU or taking the mains out if I go on holiday or if I have to turn off the power to change a lightbulb or something. Not often.

I have tried replacing the CMOS battery with two brand new ones, and the same problem still happens.


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## linderman (May 20, 2005)

motherboard problem if the battery is new / and you are hitting the save & exit command when you make bios adjustments right ?


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## ta2 (Nov 1, 2009)

Yup. I'm thinking that the PSU might be shorting it somehow. I have a spare, I just haven't gotten around to testing it.


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## Rob_Rocker (Mar 15, 2010)

@Tyree-
No the power cord to the PSU was left in the machine when I changed out the CAT5 cable. However, the PC was powered off during the Cat5 cable switch. 

What are your driving at? Really, it would not be any different than when one takes the machine out for cleaning, re-imaging, parts swapping etc. Unplug everything and plug it back up (cords and all.) How would that have anything to do with it? I've even (in the past) unplugged a CAT5 and plugged it back in with the PC up and running and I had no problems. Let me in on what you are thinking?

Thanks for the speedy response and subsequent replies. I'm almost tempted to get another P5E and have it as a back-up in the event this one croaks. I really like the E8500 and P5E, fast and quiet. I've had it for two years now with no issues until this. 

@TA2, hang in there and let me know what you come up with (i'm curious). Those ASUS boards have heavy duty capacitors, I can't see the board taking a dump, the CPU either but stranger things do happen. Anyhow, I put the PC on a bench here at work and reset the CMOS, I haven't run it but 5 minutes (seems ok except BF2 Bad Company won't launch, I'll reinstall it tonight. When I get home and go through my programs and recycle the PC a couple of times, I'll get a better feel if this main issue was an anomaly. I'll repost in a few days. Thanks TSF team and the other posters.

Rob_Rocker (PC newb)
Asus P5E -MOBO with an E8500 -CPU (no OC'ing)
2GB DDR2 Kingston -RAM
iNVidia 250 GTS w/ 1GB memory -Video card
650w "gold" Seasonic -PSU
Lian-Li P90 -Case


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## Lloyd Johnson (Mar 15, 2010)

I recently had a similar problem with my build. It was any easy fix.

The problem was that the motherboard was short circuiting on the motherboard tray, so whenever i would flip the power switch everything flickered on and then shut off. You can probably tell if this is the problem if the motherboard doesn't quite fit correctly and you cant get all the screws in.

To fix it, all you have to do is use a few motherboard stands to lift it off the tray and everything should be fine.


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## linderman (May 20, 2005)

Lloyd Johnson said:


> I recently had a similar problem with my build. It was any easy fix.
> 
> The problem was that the motherboard was short circuiting on the motherboard tray, so whenever i would flip the power switch everything flickered on and then shut off. You can probably tell if this is the problem if the motherboard doesn't quite fit correctly and you cant get all the screws in.
> 
> To fix it, all you have to do is use a few motherboard stands to lift it off the tray and everything should be fine.






*certainly worth checking into* ray:


does your board have the 9 brass stand-offs screwed into the bottom of the case ? 

or

does your motherboard mounting location have those silly "mound" looking raised dimples ? is your motherboard mounted directly to those mounds ?


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