2006? Mac Pro CPU A and CPU Overtemp LED on Plug In

Discussion in 'Mac Pro' started by Abraxen, May 16, 2018.

  1. Abraxen macrumors newbie

    Joined:
    May 16, 2018
    #1
    Hello,

    I just picked up a 2006 Mac Pro off Craigslist for $30. There are parts in it that I can transfer to another 2006 if need be, but I'd like to see if I can get this one working.

    When I plug in, seems like power goes through, the computer makes a click, and then both the CPU A and CPU B Overtemp LEDs light up solid. If I attempt to power it just click on, then off, and nothing seems to start up.

    I have no idea what the previous owners did to this thing, and my google searches have indicated this may be a sign of logic board failure. Seems strange to me that the CPUs would be over temp on a cold machine, which also leads me to believe that maybe they goofed up something with the CPUs and/or heat sinks?

    Very minimal dust from what I can see without taking anything apart.

    Just wanted to check if it's worth getting into this thing. Like I said I can take some parts into the other Macs, and while I have time to fix it if it's fixable, I don't really have the time to waste if it's a no go.

    Thanks!
     
  2. Abraxen thread starter macrumors newbie

    Joined:
    May 16, 2018
    #2
    Well I cracked it open and replaced the processors with two that were known to be working and still getting the same behavior. Also has the same behavior with just one CPU installed.

    CPU A Failure LED will quickly light up if I try to start without RAM risers installed.

    I have another 2006 Mac Pro I can take heat sinks out of, but I’m not sure if that would be the issue. I’m guessing it’s also not a PSU issue. However I don’t really know, and I’d rather not take apart a working Mac to test.

    Any thoughts as to if this is a logic board issue?
     
  3. Abraxen thread starter macrumors newbie

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    May 16, 2018
    #3
    Well I’m getting ready to sell the working 2006 Mac Pro so I figured I’d make one last check to see if anyone has any thoughts.
     
  4. ActionableMango macrumors G3

    ActionableMango

    Joined:
    Sep 21, 2010
    #4
    There are too many possible things it could be. Only way to tell would be to start swapping parts with a known good Mac Pro until it fires up correctly, but it sounds like you don't want to spend the time to do that, and I don't blame you.

    You might try to see if the 1,1 Service Manual has a troubleshooting procedure. I know the 5,1 Service Manual does.

    Personally I don't think instantly failing like that could be heat. I'm leaning toward Power Supply or Logic Board. I've also seen a short do that.
     
  5. Abraxen thread starter macrumors newbie

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    May 16, 2018
    #5
    Is there a good source for service manuals?

    I think I did finally find a post that quoted the service manual. Had to dig through a lot of forum posts and comments to find it. The first suggestion for this behavior was the PSU. So I’m going to try that out. That’s a pretty quick swap compared to pulling heat sinks.
     
  6. ActionableMango macrumors G3

    ActionableMango

    Joined:
    Sep 21, 2010
    #6
    Sorry I don't remember, I just Googled for it and found the 5,1 manual somewhere. The 5,1 manual has several pages of procedures for testing and LED indication which is used to narrow down the problem hopefully to a specific hardware component.
     
  7. Abraxen thread starter macrumors newbie

    Joined:
    May 16, 2018
    #7
    Well, swapped PSUs and no luck. I also tested the PSU from non-working machine in the working one and it’s functional.

    Have to be fairly certain at this point it’s a logic board issue.
     
  8. Lennyvalentin macrumors 65816

    Lennyvalentin

    Joined:
    Apr 25, 2011
    #8
    If overheat LEDs light up right on startup it's not going to be heat, even if you don't have any heatsinks installed at all! :) Without heatsink, it takes a (short) while for the heatspreader slug to heat saturate to the point the CPU overheats, and if there's a sink installed, even with no heat transfer paste applied you would probably even be able to boot the system to login/desktop without any fans going before having issues with accumulated heat.

    So most likely main logic board failure of some sort. Maybe a bad electrolyte capacitor somewhere, lots of stuff built in that time era had bad caps (also, these things age and die naturally on their own...) You don't happen to see any bulging or obviously damaged/leaked caps on any of the boards, do you?

    It's also possible the problem is with with one (or theoretically even both) CPU riser cards as well; old Intel dual CPU systems like this one shared a common bus for the CPUs, if one CPU is having some sort of issue it could lead to neither of them working properly. Do you have identical riser cards you could swap out with? Maybe that's what you did when you swapped CPUs previously...?`

    Anyway, good luck and stuff.
     
  9. Abraxen thread starter macrumors newbie

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    May 16, 2018
    #9
    What exactly do you mean about CPU riser cards?

    For the most part I gave up on this Mac for now. I just picked up a 2010 Mac Pro so it’s time to sell the working 2006 and my 2008. Meaning unless something is pretty easy, I’m not going to be taking apart the working 2006 any further.
     
  10. Lennyvalentin macrumors 65816

    Lennyvalentin

    Joined:
    Apr 25, 2011
    #10
    Don't the CPUs sit on daughter cards on these older Macpros? Maybe I misremember... :p
     
  11. Abraxen thread starter macrumors newbie

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    May 16, 2018
    #11
    No, directly on the logic board.
     
  12. Lennyvalentin macrumors 65816

    Lennyvalentin

    Joined:
    Apr 25, 2011
    #12
    Ah, right. Then it's just the socket 20xx (maybe socket 13xx also) mac pros that have the daughter boards I suppose. :p

    G5 powermac? It was pretty wicked, hardware design-wise.
     
  13. Abraxen thread starter macrumors newbie

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    May 16, 2018
    #13
    No, 2006 Mac Pro. 2006 though 2008 have the CPU directly on logic board.
     
  14. Lennyvalentin macrumors 65816

    Lennyvalentin

    Joined:
    Apr 25, 2011
    #14
    Sorry, my bad, I meant to say maybe the G5 also had the CPU daughter cards. I know your Mac is intel-based (it's in the thread title after all. :))
     
  15. Macschrauber macrumors 6502

    Macschrauber

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    Dec 27, 2015
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    Germany
  16. Abraxen thread starter macrumors newbie

    Joined:
    May 16, 2018
    #16
    Yes, I did try that as one of the earliest trouble shooting steps.
     

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