No video output. Possible motherboard issue?

By brandonha
Aug 9, 2010
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  1. Ok, breakdown of the issue.

    Moved in June, my tower sat in the garage until Friday. I opened the case and cleaned out the dust, during this I removed the cpu heatsink and fan assembly as it was basically caked in dust making the fan useless. Cleaned the old heat paste off the cpu and heatsink with isopropyl alcohol, applied new paste ( electrically non conductive) popped all the cards (nvidia graphics, soundblaster xfi, ddr ram and a modem of some type).

    The cpu heat sink fan also did not spin up in the nearby socket, so I had to run the line to an auxiliary case fan jumper to get it running.

    Let it all settle, plugged it in and spun it up, unfortunately it only stayed on for a minute, no video. Swapped out a known good hdd and a known good video card (from an older machine, still nvidia, still running xp.) still no video output. I've checked the seating of the cards, all good, but along the way I found a new symptom. No power comes from any of the usb ports.

    I think its a shorted mother board, but before I drop the cash and order one, I'd like a second opinion from someone more knowlegeable than I in the subject of computers.

    I appreciate any and all input on the subject.

    Brandonha
  2. mailpup

    mailpup TS Special Forces Posts: 8,421   +217

    The CPU heatsink fan should be connected to the CPU power connector on the motherboard. It should be labeled as such. If the motherboard doesn't detect the CPU fan connected to that connector, I believe it is supposed to shut down to avoid damage.
  3. brandonha

    brandonha Newcomer, in training Topic Starter

    Returned cpu fan to its power connector, still shuts down and no video output.
  4. mailpup

    mailpup TS Special Forces Posts: 8,421   +217

    Can you eliminate the power supply as the source of the problem? You might be right about the motherboard but just to be more sure.
  5. brandonha

    brandonha Newcomer, in training Topic Starter

    Checked the power supply. Voltmeter reads 12.45v and 5.36v, at least before it shut off so I'm fairly confident that it is ok.
  6. Sharam

    Sharam Newcomer, in training Posts: 538

    Just came across this, pardon the intrusion.

    Can not trouble shoot with that power supply, 5.0V rail is running too high, 5.25V is highest I would allow if I had to.

    With that much over voltage on the +5.0V and the +12V reaching the max 12.6V as well as the cleaning you mentioned, I would check the capacitors on the motherboard, if OK, replace power supply before going any further.

    Wondering what the +3.3V reads!
  7. brandonha

    brandonha Newcomer, in training Topic Starter

    Checked again, getting first hand reading this time, rather than through my uncle. 12.18v and 5.22v.

    Edit: And no pardon needed, it's not a private party, as many people who care to can make their input.
  8. Sharam

    Sharam Newcomer, in training Posts: 538

    With power supplies I like to test them off the board as well but I'll take your readings as is, what about the +3.3V and the +5.0V stand by?

    Did you have a look at the capacitors for signs of bulging and /or leaking?
  9. brandonha

    brandonha Newcomer, in training Topic Starter

    Can pretty much guarantee it's not the PSU. All voltage is within the norm on the 24 pin.
  10. Sharam

    Sharam Newcomer, in training Posts: 538

    Thanks for the report back.

    Let the process before ny interuption continue.


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