Computer will not turn on

By nimbus_racing · 58 replies
Mar 4, 2008
  1. No image on monitor. Power supply?

    Hello, sorry to start another thread on this issue but I have had a browse through the others and found nothing that seems to help. I have also looked at some of the tutorials to no avail..

    I'm fairly noob when it comes to this but I was doing my regular thing when my computer shut down randomly. It reebooted automatically and got to the asus screen where it shut down automatically again. It did this once more. After the third time it no longer rebooted (i.e. it shut down and stayed shut down).

    I tried to turn it on, but nothing. I noticed the LED on the motherboard is still on, so hopefully my hardware is still good.

    Are there any easy things I can try before switching PSU/Mobo etc? I've already tried different power cable and the unplug+hold power for 30 seconds+plug back trick. Still no good....
  2. raybay

    raybay TS Evangelist Posts: 7,241   +10

    It would be helpful if you gave us the brand and model of computer or motherboard.

    The fact that there remains a lit LED on the motherboard means almost nothing.
    The board can be totally worthless and still have that light on. It only requires 1/8 to 1/4 of a volt.
  3. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    It's an ASUS p4p800. Was trucking along nicely, no hint that anything was on the verge of going. I guess the one positive is the p4p800 isn't THAT expensive to replace if indeed the mobo is goners.
  4. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    After reading up a bit more, I've find out it's pretty much either the mobo and/or the PSU. I'm looking to replace one and see if that is the problem.

    Should I look at replacing the mobo or the PSU first?
  5. raybay

    raybay TS Evangelist Posts: 7,241   +10

    Don't give up on it yet. YOu may have tried some of these, but if not:
    First test the power supply, either with a $12 tester, or temporarily trade out the one you have with one from a different machine.
    Try rebooting in SAFE MODE (pressing the F8 key once per second as soon as you press the on button). That will be a useful test of some video cards.
    Test with only one memory module, then switch and test with the other.
    Try a different video graphics card of any quality... you are only looking for a screen that boots up.
    Try a borrowed hard drive.
    Disconnect your hard drive, and boot to a floppy disk for Windows 98, if you have a floppy drive. Be sure you have a basic setup... one memory module, video graphics connection, power supply and floppy drive. If you do not have a Floppy disk for W98, WMe, or MSDos, one of your friends will.
    Disconnect absolutely everything you can... optical drives, hard drive, etc. to see if you get signs of life in any way.
    Motherboards do fail, but rarely. CPU's almost never fail unless overheated.
    Look for such things as a CPU fan that doesn't turn. It could be bad, and the computer will not start without it. If it starts to turn when you press the ON button, there is hope. It will sometimes turn 1/2 to 3 turns if it is bad, or if the power supply is bad.
    Samething with a heatsink that has lost connection to its cpu due to inadequate thermal paste.
  6. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    thanks for the reply.

    I don't get any power at all, that is there are no fans spinning, LEDs lighting up or beeps so going through boot disks etc isn't an option.

    as a computer noob, i feel that is almost too much of a hassle. I would like to at least swap the PSU with one from my other computer and see if that works, but I really have no idea how PSU connections to other hardware works.

    Mind you moments before the computer failed, there was a burning smell (like that when you light a match) in the area. I'm not sure if this is coincidental or not, but I just thought I'd add it in case.

    Anyhow, my case+psu is a cheap one I bought for $50 so I'm leaning more towards swapping the psu to test and then replacing it if it works after the swap. As you said, mobos rarely fail and I have some faith in the product quality of Asus. So here's to hoping its the PSU and nothing further!
  7. raybay

    raybay TS Evangelist Posts: 7,241   +10

    The Power Supply appears to be very intimidating, but a test change-out is simple.
    You need to take these steps, among others.
    Remove the power plug from the wall.
    This is not rocket science. This is just a device with a lot of plugs.
    Look at how the power supply plugs into the motherboard. You need another one that has the same connectors. Some have a 20 pin connector. Others have a 24 pin connector. Some have an additional 4-pin connector.
    For regular use, you need a powerful power supply for an ASUS board, but for testing, any will do... if the plugs fit. A new replacment will cost anywhere from $50 to $150.
    You remove the power supply by removing the four screws from the back of the case, then carefully manipulating it out of the case while unplugging all the plugs to the hard drive, optical drives, floppy drive, and motherboard.
    When you put in the new power supply, the plugs can only fit one way. But you might want to draw yourself a diagram.
    This is not rocket science. Just be careful not to drop the power supply onto the motherboard, as that might damage something important.
  8. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    Ok, did a power supply swap. Sucess! The mobo works so I'll just get a new PSU.

    So I put the power supply back into the working computer it originally came from, connect everything back, but now I'm getting no picture from my monitor!?

    That monitor was always connected to that computer so I don't know what the problem could be. Monitor is definately getting power and is working (asks me to check signal cable when vga cable is not plugged in, but is just black when it is plugged in). Couldn't be anything to do with my reinstall of the power supply could it? I checked everything. Plugged the 20 pin and the additional 4 pin connectors back into the mobo and plugged the other molex cables into hdd/dvd etc (although i cant see how that may affect my monitor)

    Fix one problem, stumble across another!
  9. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    Just in case

    Remove the power cord
    Hold the ON button in for 30 secs (the computer that is, just leave the monitor on)
    Re-insert the power cord
    Turn back on

    Reply back
  10. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    thanks for the quick reply..

    tried that. still nothing

  11. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    Sorry haven't been checking here. Is this a plugged in PCI-E video card?
    If so please reseat (actually blow out dust first)
  12. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    yeah its a 7600gt dci-e.

    unplugging and replugging into mobo now..
  13. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    still no good...
  14. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    OK please test the screen ! (what on? I don't know, friends computer?)

    It's either card or screen at this point
  15. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    errrgh, swapped this and that and now it no screen will work on that computer.

    ive already unplugged and replugged the graphics card.

    what else am i missing?
  16. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29


    just took off the fan of my graphics card to clean out the dust and found this on the chip. some white cream? it is still wet. is this normal?

  17. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    Thermal Paste

    But it shouldn't be on the electronics (This may have been an overheated card (to get so wet)

    Oh and good pic
  18. kerz

    kerz TS Rookie Posts: 20

    OMG ... What’s not normal is that you took your card apart. AHHH ...
    The white stuff is thermal paste, and some thermal Paste is always wet and is needed to keep the chip cool and to spread the heat out over the heatsink it also keeps the chip from metal contact so it doesn’t weld itself to the heatsink.
    Make sure that when you put this back together you don't have the chip in contact with the heatsink. Smooth out the paste evenly then put it back together. .

    Is your card a dual head ??? …. can you hook to monitors to it ??? On some dual head cards they have 1 DVI and 1 analog. And on most newer cards the DVI is the default output. you'll need to get a DVI adapter if you have a analog monitor.
  19. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    Oh yeah, forgot to say how to put it back together !, thanks kerz :)


    Looks like a bit of dust on the RHS too
  20. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    So here I am posting from the computer that was initially the source of my problem. Got a replacement PSU and that is working fine, everything is working as per normal.

    That 7600 gt is dvi and analog. I was previously using it via analog with no problems and have tried connecting the screen via analog and dvi with adapter. Still no good.

    I will open up the graphics card again and see what I can do about spreading that paste, although how will I know if the heatsink is touching the chip?

    Bloody weird that it's stopped working the one day I used the PSU to check the other computer. I dearly hope the VGA card isn't damaged, still a darn good card.
    Any other ideas as to why it's not working?

    Edit: Due to the design of the VGA card its pretty much impossible for the two to be touching due to the four hooks on the underside. this is what the underside looks like..

  21. kerz

    kerz TS Rookie Posts: 20

    The metal plate on the fan side is the heatsink for the CPU. (or in this case GPU) Just make sure that the paste is covering the metal where the GPU indented. it only needs a thin layer.

    Did the DVI adapter you are using come with the card? If not, there are three possible types of these adapters depending on the cards DVI output. In most cases this is not the problem, but worth a check.[/url]

    The other thing to do is hook your monitor up to another PC and see if it works.
  22. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

  23. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29

    dvi adapter came with the screen. it was running through vga originally anyway. and yes I do get a picture on the screen when hooked up to another pc. this leads me to think its the graphics card. any more ideas?
  24. kimsland

    kimsland Ex-TechSpotter Posts: 14,523


    Video card at this point seems the go (or to go!)
  25. nimbus_racing

    nimbus_racing TS Rookie Topic Starter Posts: 29


    the fan on the card is still spinning as well...

    I still beleive it has something to do with when I put back the PSU. It couldn't just die on me on the same day I did the PSU test..

    psu had 20 pin + 4 pin connector to the mobo and molex cables to the drives etc
    what could I be missing?

    on the xpertvision (the manufacurer of my gfx card) site under faqs it says..

    What if my system hangs or I get a blank screen?
    Clean the golden fingers of VGA card with an eraser and plug it back to the slot again.

    edit: just tried cleaning the contacts and plugging into my lcd tv. still nothing :mad:
    I have made contact with Xpert Vision regarding warranty, dissapointing because they will probably ask me to ship it overseas and we all know what that is like..
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