No display after tinkering with computer - I think motherboard is dead

By sb3700 ยท 5 replies
Oct 25, 2010
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  1. Hi

    I think I may have a dead motherboard but I'm not sure. This is my first dead one so I have a lot of questions :)

    Yesterday, when I tried to turn on my computer, the monitor would not recognise any video input (i.e. it knew the cable was in as it went cable unplugged once I unplugged it, but it saw no video input). My first guess was a dodgy video card, but I've tried my video card in a different PC where it worked, and another working video card in my PC where it didn't work, so it's either something wrong with my AGP slot or the motherboard AFAIK.

    I've also tried another monitor and different VGA and DVI cables (normally, I connect with a VGA cable - I tried a new cable, as well as using DVI instead).

    This has been working fine for years (so it's old). I had the case open the day before to test a failing HD, and I may have messed something up on my motherboard. I do remember playing with the AGP slot with my video card to try and get my hard drive in but nothing drastic, and it was still working after I finished tinkering

    Before I go out and replace the motherboard, I wanted to be sure though.

    Current state:
    • When I power it on, the CPU and PSU fans both start. My IDE DVD drives and my floppy drives also work (receive power). This only really means that the PSU works AFAIK
    • My hard drive (SATA if relevant) may or may not work - the fans are louder than the normal running sound of my HD. It doesn't appear to ever reach Windows though as I can't see it on the network or through LogMeIn.
    • My internal speaker (the beeper) doesn't appear to work - when I started the comp with no RAM, nothing beeped. This may be because the speaker connector is inserted wrong - it's meant to be a 4-pin connector with (5V, Gnd, Gnd, Speaker) as the pins according to the mobo manual. My connector has 2 pins only (+ (yellow), <empty>, <empty>, - (black)) which doesn't seem right. The + and - are written on the speaker connector cable. I've tried swapping the connector around but no luck. I vaguely remember that I've heard it beep before so it not working is a new problem.
    • I've tried using the Clear RTC Ram setting which should reset the BIOS.
      I've tried removing my video card and connecting the monitor to the socket for on-board graphics. It didn't work. This could be because it's never worked (first time using it), it's broken, or its disabled in the BIOS.
    • I've looked for loose screws but found nothing so far.
    • I've disconnected nearly everything inessential.

    Steps I'm still taking:
    • Check all the ICs to make sure they are in properly
    • Check HD in another comp
    • Try motherboard outside comp case (to avoid any shorting with the case / to get a better look)

    Motherboard is P5P800-VM
    Graphics card - not sure. I can find out if relevant but its an Asus

    Also, is it safe to use a multimeter on the motherboard. I want to check the speaker and also use it to check if its alive current, but I have no idea how.

    Any other ideas? Is my motherboard definitely dead?

    Thanks in advance
  2. Route44

    Route44 TechSpot Ambassador Posts: 11,984   +72

    You certainly have done a great deal of diagnostic work already. The first thing that jumps out at me is the harddrive.

    Try this: When you slave it to another system access this harddrive through that system and do a full harddrive diagnostics on it.

    Did you check the BIOS to see a) if this harddrive is recognized in the BIOS and b) if the onboard sound was enabled or disabled in the BIOS?

    Check the motherboard's capacitors for any bulging caps.

    * Keep in mind if you need a new motherboard, depending on how old it is, you'll at least need new RAM and possibly video card.
  3. sb3700

    sb3700 TS Rookie Topic Starter

    Thanks for replying.

    I've confirmed it is an issue with the motherboard. I found an older motherboard and tried connecting everything to it and it works fine. Unfortunately, that old motherboard is too big for my case.

    Is the bulging caps related to www . (sorry for malformed, can't post URLs yet, happy to delete if I shouldn't be posting links)

    Regarding hard drive: hard drive works fine in other computers, and right not I'm running it through a USB external enclosure with no problems. Doing diagnostics sounds like a good idea though.

    I couldn't check the BIOS because there was no display and I don't know my BIOS well enough to change settings blind.
  4. jamesodriscoll

    jamesodriscoll TS Rookie Posts: 91

    Hi sb3700,

    Regarding your BIOS. I doubt there is a BIOS issue as you would still be able to get an image on the screen but in case something has changed you can try re-setting the BIOS.
    In order to do this all you need to do is remove the CMOS battery from the mobo and leave it out for 10 mins. (this is longer than is needed but i tend to leave it this long anyway).

    This will re-set the BIOS to the default settings and you can try plugging in your hardware again and see if this helps. As i said i doubt this is an issue because even if the BIOS had gone wrong you should be able to get some image on boot.

    If you want to test the mobo out of the case then you could do the following:
    • Place the board on an antistatic surface
    • Locate the front panel of the mobo and locate the POWER button pins. (normally labled POWER or PWR)
    • Plug in a KNOWN working PSU unit and using a small flathead screwdriver gently connect the two ON PWR pins. on the rare occasion you have 3 pins for the Power it will always eb the middles pin and on of the end ones :p)
    • If the CPU fans starts and the PSU unit starts then there is power running throught the board.
    • If nothing happens then you now know it could be one of two things. The mobo or the CPU. I would then recomment replacing the CPU with a KNOWN working CPU and retrying the test.
    • If, again, nothing happens then you know that the mobo is at fault. IF the cpu fans starts and the PSU unit starts with the "known working" CPU in then you know that there is a fault with your old CPU.

    Hope this helps
  5. sb3700

    sb3700 TS Rookie Topic Starter

    Thanks James

    I've done the reset. I removed the battery, moved the Clear RTC jumper which clear the BIOS settings and waited about 5 minutes. I agree that the BIOS is not the issue but I had read somewhere that the problem could be caused by the BIOS being "confused".

    I've tested the mobo both in and out of the case (resting on an anti-static mat). I've used my current PSU which I replaced maybe 6 months ago and which works when I've tested with another motherboard. On my (broken) mobo, both the CPU fan and the PSU fans power up.

    It could still potentially be a CPU issue, but right now I think it's most likely the motherboard. I'll check for bulging caps, shorted pins and other physical issues which I might be able to repair (or maybe not?). Otherwise, I'll just replace it (and probably the whole computer).
  6. jamesodriscoll

    jamesodriscoll TS Rookie Posts: 91

    No probs

    tbh if the mobo is broken you cant really fix it so it may be time for an upgrade lol

    glad i could help


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