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Computer turns on, then off, then on etc..

By Kidlife · 17 replies
Sep 20, 2007
  1. Hello,

    I am having a problem with my computer, and while I'm pretty sure the motherboard is to blame, I thought I'd check for input before I buy a new one. My computer has been working wonderfully since I built it sometime in May, until yesterday, when I went to turn it on. Here is what happens when I hit the power switch: the computer starts to power up (power LED lights up, fans start spinning, hard drive starts spinning). About 2 seconds after I hit the power button, the computer shuts off, and stays off for about 2-3 seconds; then it will turn itself back on, but of course only for 2 seconds. This cycle of on/off/on/off will continue forever until I either hit the switch on the back of the power supply, OR if I hold down the power button for about 5 seconds.

    OK, so my first reaction was it had to be a problem with either the motherboard or power supply. The first thing I did was unplug everything from the motherboard, leaving only the CPU attached, the power LED wire, and of course the MB power connector and 12V CPU power connector. I then turned the computer on by shorting the power jumpers. Same result.. the CPU fan would twitch, the power LED would come on.. and then shut off.. turn back on.. rinse, and repeat. The next thing I tried was swapping the power supply with a known working one. Same result.

    So.. I'm guessing there is something wrong with the motherboard. I've never heard of a problem like this.. it seems quite weird to me. Of course, I'm not too great with computers, so I feel I might be missing something obvious. Any ideas on something I might have missed would be appreciated :) Otherwise its time for a new motherboard :mad:

    Oh, I don't have another computer that I can test the CPU on... not sure if the CPU could possibly be the problem.

    Gigabyte GA-965P-DS3 Motherboard (rev 3.3)
    Intel® Core 2 Duo E6600
    Mushkin XP2-6400 2x1Gig
    Antec NeoHE 500W HE Power Supply
    XFX GeForce 8800 GTS 320MB
    WD Caviar SE 160GB SATA

    Thanks for any ideas!
  2. AlbertLionheart

    AlbertLionheart TechSpot Chancellor Posts: 1,997

    I think it may be the power supply unit (PSU). This may be overheating and the thermal cut-out is doing what it should. Check the fan(s) in the PSU work OK - if not, try cleaning them with a small clean paintbrush.
    Best bet is to try another PSU - maraginally cheaper and a lot easier to replace than the motherboard.
  3. Exonimus

    Exonimus TS Rookie Posts: 71

    I'm not sure overheating could be the problem. Not two seconds after booting up. But yeah, I would also try another power supply, and if that doesn't work, it's probably the motherboard

    edit: you were talking about the fan in the PSU, sorry. Reading is an art by itself :p
  4. Tedster

    Tedster Techspot old timer..... Posts: 5,746   +14

  5. I_love_FionaXie

    I_love_FionaXie TS Rookie

    You could try doing a CMOS reset on the motherboard.

    Btw did u do a OC on this motherboard?

    just curious

  6. Kidlife

    Kidlife TS Rookie Topic Starter

    I have swapped the PSU with a known working one and still have the problem. I'm going to send the board to Gigabyte as its still under warranty, and I can't think of anything more to try. I appreciate all the suggestions :)

    No, this board was only 4 months old, running at stock speed.
  7. DeepBlu

    DeepBlu TS Rookie

    Try to start your system with 1 piece of RAM, try each RAM alone once. Also Could be overheat, but not with PSU , with the CPU , CPU overheat causes the mobo to switch off. well it's not enough time for the CPU to go overheat as it just started, but as the processor is powerful which making it go hot fast, a check won't harm, try to touch the processor heatsink while starting to know if it is over hot , but watch your fingers from getting fried, also make sure that the heatsink is well seated on the processor itself, tell me how it goes.
  8. coolade

    coolade TS Rookie

    Kidlife - I am currently having the exact same problem. Power will cycle (green light on mobo) for about 1 second, then turn off and back on again, till I switch the PS off... When I take out the 8-pin CPU connector (which I'm told is not a good idea) the mobo seems to have consistent power to load up, including the video card. However, obviously the CPU isn't running at this point.

    I'm running:

    Corsair 620W PS
    Adata ddr2 800 RAM
    ABIT IP35-E Mobo
    EVGA 8800GTS

    I already sent back the mobo, cpu and memory for testing. Apparently the first mobo wasn't working properly, so they replaced it, tested the components and sent a new one back. I just tried to load everything up yesterday and still no luck, which was frustrating as all hell...

    I originally thought the prob was w/ my ram b/c it requires 2.1v to work, and the mobo default is 1.8v. They said they changed the voltage for me, but I suspect maybe they didn't. I'm going to buy some lower voltage ram to try and boot up so that I can change the voltage in bios.

    I've tried two different power supplies, both of which work when I hook it up to a different system setup. Can't be that. I'll post more details as I try more stuff out and I hope you can do the same...
  9. Kidlife

    Kidlife TS Rookie Topic Starter

    Coolade - As of right now, I've sent my motherboard back for repair/replacement as I'm pretty sure that is the problem. I will let you know what happens when I get it back.
  10. meltdown05

    meltdown05 TS Rookie

    The problem can be attributed to a variety of things, but I have mainly seen this when a CPU is faulty. A few days ago I was testing an older CPU in my system (which is a great system that I am using to write this post with) to see if it was still functioning properly so I could sell it. After putting this older CPU in my system to see if it started and functioned properly, the system came on for 3-5 secs and then shut off, and continued to repeat this cycle on its own. When I put my new CPU back in, the system started up and works as usual. This has happened to me countless times and this was the most recent time. Alot of these cyclical "on-off" issues that people have with their computers can be attributed to a bad CPU. The computer shuts off because the CPU isn't starting the POST process and the system cuts off. Unless you have an ancient model PSU, I don't believe it is the culprit. You did well in shipping the mobo in for a replacement because that is probably the only other component that could cause your problem. However, I would look into trying another CPU or perhaps shipping it in for a replacement as well. Hope this helps because I have been building computers for years and know how frustrating it can be. Stick with it and good luck
  11. sol1109

    sol1109 TS Member Posts: 43

    My kids computer recently did the same thing and it took me four days to figure out how to stop it. It turned our to be something related with an auto update to XP SP3. Once I removed that and locked out auto update it has been stable since. The problem was how to remove it since I could not get the computer into a stable mode to begin with. It turned out that on BSOD their system would auto reboot. This was disabled in the BIOS and then I set the CD drive as the first boot device. Using the windows CD and option 4 from this site I was able to remove SP3 if you think this could be it give it a try.

  12. Halobec

    Halobec TS Rookie

    Gigabyte Mainboard BIOS loop

    Gigabyte motherboards often power down and start back up after you make a change in the BIOS like setting the memory timings or something similar. If the changes made are not right, Gigabyte motherboards can go into a BIOS post loop, In other words, if you cannot reset the BIOS as defined in the manual, the motherboard is bricked.
  13. MassEffect

    MassEffect TS Rookie

    same prob

    hi all

    i have the same problem on my new system but it has been working fine untill today so at the moment i am flashing the bios and you let you guys know if that works or not
  14. AlbertLionheart

    AlbertLionheart TechSpot Chancellor Posts: 1,997

    Have you tried will all the USB devices disconnected? Sometimes these especially powered hubs can cause this!
  15. MassEffect

    MassEffect TS Rookie

    i have tried resetting with no avail ( Disappointment ) so then tryed taking out all parts and testing them one by one ( Fail ) was speaking to someone and they reckon it the power suply
  16. AlbertLionheart

    AlbertLionheart TechSpot Chancellor Posts: 1,997

    I suggested that in post #2 - now might be a good time to revisit that if you have not done so!
  17. MassEffect

    MassEffect TS Rookie

    ok im using a 500 Watt and have a spare 350 Watt ps woundering if it would run this system

    MOB - Gigabyte Ga - er45 - up3p
    Graphic - MSI N250GTs
    CPU - Intell Core 2 Duo @ 3.0Gbz
    Ram - Gskill @ 4Gb
    HDD - 1Tb

    and the ps is a 500 Watt antec earthwatts
  18. AlbertLionheart

    AlbertLionheart TechSpot Chancellor Posts: 1,997

    It would be good enough to test for the fault to find out either way if your 500W PSU is the culprit.
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