Mac Pro 2008 3,1 faulty logic board?

Discussion in 'Mac Pro' started by warmachine4pres, May 3, 2015.

  1. warmachine4pres, May 3, 2015
    Last edited: May 3, 2015

    warmachine4pres macrumors newbie

    May 3, 2015
    This post might get lengthy as I want to be thorough in my explanation so I can get a proper diagnosis.
    I recently bought a Mac pro 2008 3,1 (2x 2.8 GHz quad-core, 8gb ram, ati 2600xt) and it ran fine when I first booted it up (running osx 10.8 at the time). Although the computer was working, the previous owner let a lot of dust accumulate inside. I installed Yosemite on the machine then shut it off. After that, I took the computer apart for dusting. I dusted each part with an air compressor then I reapplied heat sink paste to the CPUs. After reassembly, I press the power button and the GPU fan starts spinning at full speed. There is no chime and the computer doesn't boot. I removed the graphics card and power on again. The front light doesn't blink, so the computer isn't recognizing that there is a problem. Next, I removed the ram, same thing, no blinking front light. I tried resetting the smc, checking the diagnostic LEDs ( but nothing seems to work. I did as much research as I could and concluded that it's a logic board issue. I thought I'd ask here first before buying one though. So TL;DR Bought a working but dusty Mac pro, dusted it, and now it doesn't work and am wondering if I should buy a new logic board or not.
  2. nigelbb macrumors 65816

    Dec 22, 2012
    You have done much much more than simply dusted it as you have removed the CPU heatsinks to apply new thermal paste. Did you remove the CPUs? have you bent any pins?
  3. warmachine4pres thread starter macrumors newbie

    May 3, 2015
    Yes I removed the CPUs. I don't think I bent any pins because the diagnostic lights would say that it doesn't recognize the CPUs.
  4. warmachine4pres thread starter macrumors newbie

    May 3, 2015
    I'm assuming that I either have a bad logic board or a bad PSU. I have no way to confirm either though.
  5. rueyloon macrumors regular

    Sep 24, 2013
    in case you are running extra drives using the internal "free" sata, don't. I had the same problem until I still using those ports and the computer is stable once again.
  6. Draeconis macrumors 6502a

    May 6, 2008
    Carefully reseat the CPU and heatsink, sounds like the Mac Pro isn't seeing the fan on the heatsink.
  7. CLMNT macrumors newbie

    May 5, 2015

    The compressor has an air filter ?
    There can be projections of water / oil and little cause short circuit.

    My mac pro is also a bit dusty but I restrain myself to spend a compressor as didn't have filter
  8. warmachine4pres thread starter macrumors newbie

    May 3, 2015
    What makes you say that? It is only the GPU fan that spins at full speed. The other fans kick in about 5 seconds after power on, but they run a normal speed.

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