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My PC config (4 years old):

  • Motherboard: ASUS M2N 68 - AM Plus
  • CPU: AMD PHENOM X2 545.
  • HDD: WD 320 GB
  • RAM: 2 GB DDR2 800Hz
  • Power supply: Intext 450W switching PSU

About a month ago my PSU was gone with bursting sound. The green LED light on motherboard was not on, so I purchased a new 450 W Zebronics switch-mode PSU. The computer started and worked fine for 2-3 hours.

Then after some days I found its just powering off randomly. I checked the temperatures and it was heating up, so I took out CPU fan cleaned it and applied new gel.

But then at latter stages the frequency of restarts increased and some times even the CPU fan started and stopped in 1 mins or less.

Then again after 2-3 days the newly purchased PSU was gone and I got it replaced with same model.

Now I am still facing same problem, I tried using my PSU on other machine and it worked fine there, but my machine did not worked fine with alternate PSU.

Sometimes after starting up (may be 1-2 failures) it works perfect for 2-2.5 hours. If I start it again latter it just restarts in every 5-10 mins

Also one thing to notice is , if I remove the HDD power supply from PSU or remove the 12V ATX cable (4 pin) from the motherboard then CPU fans starts and continue to rotate, but off course system does not start.

I am confused about this. Please advice. Thanks.

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Sounds like a (alsmost) short circuit. Something is drawing to much power. –  Jan Doggen Aug 16 '13 at 7:23
    
Could you try removing the HDD and booting from a bootable USB drive or CD just see if the issue still remains? That way you would see if it's the HDD that is faulty. Maybe the system could also be made to boot with the 12V ATX connector disconnected from the M/B (using Windows safe mode or some other stripped-down mode of whichever OS you are running). Basically disconnecting or replacing one component at a time and testing to see the results should allow you to find the part that has failed. If the rebooting is due to excessive current draw, the faulty part should also heat up noticeably. –  zagrimsan Aug 16 '13 at 7:41
    
Thanks for your replies. I tried to remove each component and tested it, but it does not work after HDD/12V power supply is connected.Here point to note is, if 12V not connected then, it works even after connecting HDD. Also I may try running it with Bootable USB or using Ubuntu from it. But the system won't start up if I remove 12 V connector, although keyboard/mouse and hdd lights turn on, nothing happen on screen. As soon as connect 12 V power cable, it starts booting process. How can I start booting after removing that cable in Win7 or winXP , dual boot mode(stripped-down mode). –  Pushkar Aug 16 '13 at 8:33
    
Regarding short circuit , i have cleaned the front (visible ) side of M/B , but haven't checked the back side, will also clean it up tomorrow. –  Pushkar Aug 16 '13 at 8:37
    
You have a weird generic brand power supply get a named brand or get a much bigger one. The 450w rating on the Zebronics is likely only achievable at 60 Fahrenheit. (yes some companies cheat like that). Get a corsair, thermal take, any of the name brands. –  cybernard Aug 17 '13 at 23:42

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