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Lights flash, fans turn on and off, comp remains off.

By pph4m
Mar 24, 2006
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  1. Hi, I would firstly like to apologize for not being able to update my user CP or tell you what my CPU/Mobo is. I can't get my computer to turn on and can't access the info.

    This happened while I was trying to reset everything on my computer (because there was a problem with my NIC). I unplugged everything and replugged them into their respective places, and now I can't seem to turn my computer on. Everything was working fine (except the NIC) prior to my resetting. Now the problem is when I turn on the power, there would be a small delay before it would turn on, and when it does turn on, the lights in front of the computer (for the on switch) flash, the flashing intervals are synchronized with the rate the CPU fan turns on and off. The case fan is running constantly however and it is blowing out cool air. I have done some searching on the forums, and I have heard that it was because I unplugged the 12-20 wire that connects the power button (in the front) to the CPU. I unplugged this wire and the fans still turn on and off, except the front LED's can't flash. If anyone can help me, that would be most appreciated.
  2. lewekleonek

    lewekleonek TS Rookie Posts: 59

    You gotta do some more diagnostics.
    But before I'll start listing them, I have one question:
    Before you've removed components from your computer did you un-plug it from AC outlet? Cause if you didn't you may've damaged motherboard or any other component for that matter. I know it sounds silly but I'm just making sure.
    Anyway, do as follows:
    Unplug the power. Open the case and re-sit you memory modules and if you have to re-sit your CPU chip. Re-sit all your add-on cards (sound, video etc.) Make sure you re-install the CPU heatsink properly. Make sure that all cards and modules are snug and properly sitted in the motherboard.
    Note! Dont' ever operate your CPU without properly installed heatsink, ever!
    Plug it back in and the try to boot. If it's still no go:
    Unplug it. Pull all the cards out except for the video card. Disconnect all your drives: hard drives, cd/dvd-rom/rw drives, floppy drive(s) etc. Actually disconnect everything from you motherboard except for: CPU, 1 memory module and video card (and of course power supply - make sure the 12V+ cpu plug is in the motherboard!). Plug in and power on. See what happens. If it's still no go move the memory module to a different slot; power on; still no go - pull the video card out: plug-in power on; still no go:
    - Your power supply, motherboard, memory module or CPU has gone bad - you gotta swap them out with differnt component to test if this fixes the problem; start with power supply, then memory module, then motherboard, then cpu.

    If it did on the other hand boot up with barebone set of devices: power supply, motherboard, cpu, 1 memory module, start adding componets:
    1. video card - boots o.k. go next step. it does not replace your video card
    2. your main hard drive
    3. cd/dvd-rom/rw drives one-by-one
    4. etc. etc.

    Good luck!
    Debugging requires a lot of patience and a very methodical approach. Try not to miss steps.
  3. pph4m

    pph4m TS Rookie Topic Starter

    thanks for the tips lewek, I managed to find my problem. turns out it wasnt any of my hard drives or cards, it had something to do with resetting power supply. I had to change it from 115 to 240 and back again for it to function properly.
  4. howard_hopkinso

    howard_hopkinso TS Rookie Posts: 25,948   +19

    I`m glad you`ve solved your problem.

    However, I`m a little concerned about your psu. I don`t know why you`ve had to change the voltage and then change it back again.

    It might be a good idea to consider getting a new, good quality psu.

    A faulty psu can cause untold damage to a computer system.

    Regards Howard :)
  5. Shadowrunner

    Shadowrunner TS Rookie Posts: 149

    Somethin's shorting by the sounds of it. It could be any number of things from an extra mount on the mobo or even a bent CPU pin. I'd say do a complete and fresh rebuild. Works for me, I love rebuilding my computer. Just watch teh CPU and the RAM, those things are pretty touchy ya know? Itt'l be in your best intrest to ground yourself aswell, this can be done by taking the PSU out (presuming you've already done it in the rebuild) pulg it in, turn it on, (PSU only) and tap it a few times, ir just touch something meteal. Hope this helps. ;)
  6. Shadowrunner

    Shadowrunner TS Rookie Posts: 149

    ahh already done, i dont tend to read things fully, but if it happens in the future after you've just built a new system, do it again...
  7. lewekleonek

    lewekleonek TS Rookie Posts: 59

    That's a strange one indeed. This is not a good power supply if you have to do that. I've never run into such a problem. Is this a brand/labeled pc or a custom made one. What kind of a power supply you got there?
  8. Tedster

    Tedster Techspot old timer..... Posts: 10,074   +13

    brands mean nothing in the power supply world.

    go to Tom's hardware and read about their testing of PSUs.
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