Power Issue - Mac Pro 2008

Discussion in 'Mac Pro' started by EWelton, Aug 14, 2013.

  1. EWelton macrumors newbie

    Aug 14, 2013

    I have a Mac Pro 2008 3,1 2.8ghz 8 core. Recently, the computer would not power on. I took it to the Genius Bar, and the tech said it was most likely the power supply but for me to take it home, disconnect the video card, and to power it on. If it powered on, then the video card was bad. If not, it was the power supply. When I disconnected the video card, the computer powered on.. suggesting a bad video card. But, when I reconnected the video card, the computer powered on and worked fine for a couple weeks. Then, the computer started cutting off in the middle of functioning. It would power right back on, but randomly cut off sometimes. I went out of town for the weekend and shut down while I was gone. Ever since I came back, it will not power on. The power light on the front comes on briefly, you hear a click, and that's it... doesn't stay on until the chime. I've tried unplugging the video card again, pressed the system reset button on the logic board, and removed and reset RAM boards. I have pressed the DIAG_LED button and verified that it is receiving trickle power. After 2 or 3 attempts at starting the computer up, LED's 5 & 6 marked OT light up solid red, which I read means a CPU temp issue. Seems to be a failed power supply from my reading, but want some input before I go spending money on one if the problem may be something else. Any suggestions on further troubleshooting or any expertise on this?? THANKS! Eric
  2. Korican100 macrumors 6502a


    Oct 9, 2012
    Yea that sounds like a bad power supply. Which 3,1's are notorious for having that problem. Once you replace it, I suggest a quality UPS to power your beast, keep the power supply in great shape.

    When my first power supply went bad, I had those moments that it would start working randomly out of the blue, then it eventually completely died.
  3. OS6-OSX, Aug 16, 2013
    Last edited: Aug 16, 2013

    OS6-OSX macrumors 6502a


    Jun 13, 2004
    The 3 "free" attempts:
    Zap the Pram
    Reset the SMC
    Take the Pwr Supply out and give it a good cleaning!:cool:

    Attached Files:

  4. Mactrunk macrumors regular

    May 12, 2005
    PSU replacement on 2008 MP was pretty easy for me.
    There are videos on youtube.

    I was afraid, but found it to be a fun and rewarding task.
    Local shop was asking $600 for the job.
    Back when I did it, I found a PSU for $220.
    Took me 30 minutes and saved me a bunch.
    Worked great and fixed the problems.

    Still running solid.

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