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Computer won't stay on for more than a few seconds

Last response: in Components
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December 25, 2009 7:22:15 PM

I recently purchased a Corsair TX750W 750 watt PSU for my computer along with a Radeon HD 5870. When I was first installing the power supply I turned on the computer without the 4 pin power connector to the cpu connected a few times because I had forgotten to plug it in. After successfully installing both the power supply and the video card I used my system for gaming for about 6 hours and then went to bed, shutting the computer down normally.

The next morning when I tried to turn the computer on it powered on for only a couple of seconds before turning off again. This happened every time I tried to turn it on so I opened up my case to check the connections. All the connections were properly connected so I thought maybe It was something to do with my video card. I tried powering on the system without the video card connected (using the onboard card) and still it did not turn on for more than a few seconds. When I disconnect the 4 pin connector to the motherboard for the cpu the computer turns on and stays on but of course, does not boot. What does this mean? Is the mobo connector shorted out, the PSU bad, the CPU fried, or all 3?

More about : computer stay seconds

a b ) Power supply
a b U Graphics card
December 25, 2009 7:52:26 PM

I'm sorry I can't be of much help but I can say it is unlikely that the PSU is bad and even more unlikely that the CPU is fried.
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a b ) Power supply
a b U Graphics card
December 25, 2009 8:04:46 PM

The 4 pin cpu fan has to be connected or the system won't boot; this helps prevent damage to the cpu from overheating. Try a different power supply even if it's a cheaper unit. If that doesn't work, then you may have a bad motherboard. Request an rma from the manufacturer's website unless it's only a few days old. Newegg is pretty good about rma's; the manufacturer will generally take 24 hours to respond to an rma request, and about 2-3 weeks to replace the board. Don't expect a brand new box with all accessories; they will send you a tested used board unless it's your third or fourth rma for the same board.
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December 25, 2009 11:05:02 PM

Thank you for your help o1die, however I thinik you are misunderstanding the connector I am talking about due to my being vague. By 4 pin connector I mean the black 4 pin connector that connects to the motherboard near my CPU(molex I think its called?), not the white 4 pins for the fans. The fans still spin with the 4 pin disconnected but the computer does not boot. I am going to try reconnecting the old PSU to determine if the PSU is indeed the problem. Any more help would be much appreciated. Thanks again.
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December 26, 2009 12:07:32 AM

Okay so I reinstalled my old psu and video card and tried to power on my system but I had the exact same problem. When the 4 pin (molex?) connector near my cpu has the corresponding plug in it my computer will not stay on for more than a second, but when I disconnect it my computer turns on and stays on. However when the 4 pin is disconnected the computer will not give a video signal or boot, I assume this is because the 4 pin connector is supplementary power to the mobo for the cpu. In any case, I believe I have ruled out the PSU as the cause of the problem. This leads me to believe that the cause of the problem is the mobo, I must have caused something to be damaged during my installation of the PSU.

EDIT: I found out the name for the 4 pin connector - it's the 4 pin EPS12V connector to power the CPU.
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December 26, 2009 12:25:14 AM

Sounds like a CPU problem if the CPU was overheating it might be fried or the it`s the PSU but it is highley unlikely.
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April 28, 2010 1:45:52 AM

Im running into a very similar problem.
But the CPU doesn't have time to overheat. The power only stays on for a second...maybe less.
Ive replaced the MOBO and PSU, TWICE.
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a c 104 ) Power supply
a b U Graphics card
April 28, 2010 6:38:07 AM

According to this link, that psu doesnt have a 4pin Mobo plug, it has an Eight pin plug, the only square 4 pin I can see listed there is part of the main Motherboard plug, 20+4, the ones listed as 'peripheral' are molex's btw, what model is your mobo and maybe we can narrow this down a bit :) 
http://www.tigerdirect.com/applications/searchtools/ite...
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April 11, 2013 5:05:35 PM

Ryugen said:
I recently purchased a Corsair TX750W 750 watt PSU for my computer along with a Radeon HD 5870. When I was first installing the power supply I turned on the computer without the 4 pin power connector to the cpu connected a few times because I had forgotten to plug it in. After successfully installing both the power supply and the video card I used my system for gaming for about 6 hours and then went to bed, shutting the computer down normally.

The next morning when I tried to turn the computer on it powered on for only a couple of seconds before turning off again. This happened every time I tried to turn it on so I opened up my case to check the connections. All the connections were properly connected so I thought maybe It was something to do with my video card. I tried powering on the system without the video card connected (using the onboard card) and still it did not turn on for more than a few seconds. When I disconnect the 4 pin connector to the motherboard for the cpu the computer turns on and stays on but of course, does not boot. What does this mean? Is the mobo connector shorted out, the PSU bad, the CPU fried, or all 3?


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