MoBo light on, but computer turns off and on endlessly?

Hello, I just put together my first build last night. I turned on the PSU switch and the green mobo light came on. Then I pressed the power button on my case. Lights came on, fans began to spin, and for about 5 seconds everything seemed fine. Then it all just turned off, for about 5 seconds. Then on again for 5. Then off again, then on again. Over and over again until I turned off the PSU switch. The mobo light stays on the entire time, though.

Here are my components:

Case: Rosewill CHALLENGER Black Gaming ATX Mid Tower Computer Case

Power Supply: COOLER MASTER eXtreme Power Plus RS500-PCARD3-US 500W ATX12V v2.3 Power Supply

Processor: Intel Core i7-3770K Ivy Bridge 3.5GHz (3.9GHz Turbo) LGA 1155 77W Quad-Core Desktop Processor Intel HD Graphics 4000 BX80637I73770K

Motherboard: ASUS SABERTOOTH Z77 LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard

Memory: Seagate Barracuda ST1000DM003 1TB 7200 RPM SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive

Hard Drive: G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1866 (PC3 14900) Desktop Memory Model F3-14900CL9D-8GBXL

Video Card: EVGA 02G-P4-2678-KR GeForce GTX 670 FTW 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card

Hopefully someone can help me shed some light on this. Thanks!
18 answers Last reply
More about mobo light computer turns endlessly
  1. 1st thoughts are the PSU or something not connected correctly. Did you breadboard before installing components?
  2. Since I don't know what breadboarding is, I'm pretty sure the answer is no... I did try to do an external build before installing as advised by the Newegg YouTube tutorial, but I could not find the little beeping device that they used to test the build. So I just began installing to my case.
  3. Sorry...breadboarding is assembling outside the case before installing. Most (maybe all) ASUS boards lack a speaker to test via sound.
  4. hmmm, does anything show up on a monitor???

    there might be some more details on screen
  5. I've connected an HDTV to my PC using and HDMI cable, but the TV just says there is no signal. Is there anything else besides an HDMI cable that I need to hook up my PC to the TV?

    It may also be possible that the computer isn't staying on long enough for the TV to respond...
  6. Another question - is the PSU fan supposed to be constantly spinning assuming that the PSU is not defective? I just noticed that the PSU fan stops spinning at the same intervals that the computer switches on and off. Is this an indication that the PSU itself is broken?
  7. PSU fan should run continuously. If it turns off, that means a power loss to the computer.

    Sounds like a faulty PSU.
  8. I just looked at the links for your PSU and your GPU. It states that the PSU has only one 6 pin power cable and the GPU requires two 6 pin power cables.

    Possible that you need a higher wattage PSU? I would recommend this an an alternative:
  9. My GPU came with two 6 pin power adapters so it wasn't an issue, thankfully. But I think you are right about needing a higher wattage PSU. Thanks for the recommendation.

    If the PSU fan is supposed to spin continuously, then the problem with the current build is most likely is the PSU not staying on. I will contact Newegg about a return. Hopefully they will waive the restocking fee since they sent me a defective component.

    Thanks for your help!
  10. its possible the psu is shutting down not because it is bad, but because something is making the system shutdown. If the system shuts down, the psu will also
  11. So much for my definite culprit. :( I guess I'll have to test the PSU to be sure. Be back w/ the results.
  12. I'd suggest the PSU, mainly due to the power you're pushing through that.

    I've learned my lessons before, remember you're powering roughly a 1500 dollar computer, do you REALLY Want to trust that to a 40 dollar PSU? Go with a brand name, Antec, PC power and cooling etc.

    For an example, my horror story.

    Few weeks ago computer would begin to shut off randomly believed it was a HDD problem.

    Checked later on, Power supply was running 2 volts on the 3 volt rail. Don't buy a cheap power supply

    At the price it is I'd suggest get an Antec, Corsair or PC Power and Cooling. They tend to be stable. Forewarning, don't get any low cost "Green" or such, they might be high efficiency but they're often lacking.

    Also check when you seated your CPU it's properly seated and no thermal compound has gotten on the contacts (Seen it before)
  13. The more i think about it, the more confused I am.

    It sounds sort of like the PC is shutting itself down, as if the CPU were getting too hot.

    However, when PC's shut down to protect themselves, they shut down, they don't enter a reboot sequence.
  14. Thank you all for your input. I think I know where the problem is, but I still don't understand.

    After perusing my MoBo's manual, I realized that it has a Power On Self Test LED indicator feature. And the CPU light is on. :( What could the issue be? Both the MoBo and the CPU are LGA 1155.

    Amorenn, could you elaborate on your last comment? What are the "contacts" that you're referring to that should be clear of thermal paste?
  15. I believe he is referring to the contacts on the processor, the pins...

    that would explain why the cpu light is on

    the cpu is either not seated properly, or like Amorenn said, paste could be messing up the connection, shorting pins or something.

    You should remove the cpu, carefully inspect the pins on the bottom as well as the holes on the motherboard for excess thermal paste or anything else that shouldn't be there.

    If the cpu and motherboard are clean, and the cpu is properly installed you might have a bad CPU. It's rare, but not unheard of.
  16. Thanks for elaborating. Before I go about removing the CPU and checking for excess paste, I'd like to confirm one thing: is connecting the CPU fan to the MoBo the same thing as plugging in power to the CPU? I keep reading on forums to make sure that the CPU is plugged in, but I'm not sure if the CPU fan connection is also the same thing as the CPU power connection.
  17. No.

    Plugging in the fan provides power to the fan and thats it.
    The CPU has no dedicated power connections, it just pops into the motherboard.

    When you power on the system does the CPU fan spin?? If not that could cause the system to shutdown, because of heat or just because it requires the fan to spin.

    The forums that say to make sure the CPU is plugged in mean to make sure the CPU is properly seated, and to make sure the CPU fan is plugged in. If the CPU fan is not working, the CPU can build up heat quickly, and possibly overheat.
  18. Well, I solved the problem of it booting on and off. The problem was so basic it's embarrassing to say what it was... I has connected the 24 pin power cable, but not the 4/8 pin. I connected that and now it's powering up just fine. CPU_LED is now off. I guess mistakes just don't get any more noob than that. Thanks to all who offered their help on this. I have two new problems now, but I'll start a new thread for that.
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