Mac Pro 5,1 Backplane Logic Board failure

Discussion in 'Mac Pro' started by macguru9999, Apr 27, 2019.

  1. macguru9999 macrumors regular

    Joined:
    Aug 9, 2006
    #1
    Yesterday my Mac Pro 5,1 Backplane Logic Board failed on my spare computer. Its only powered on sometimes, I installed some known good ram in the cpu tray, powered up and it shut down. Investigation revealed it would briefly get power then sparks came from these surface mount components just below the second drive bay, and of course it shuts down. I have stripped the machine and ordered another 5,1 backplane. Any idea what these suckers do ? (see attached photo) While I have had the machine I have just had a 680gtx plugged into the 2 power sockets but of course i dont know where the machine has been for the last 8 years ! P1010146.jpg
     
  2. tsialex macrumors 601

    tsialex

    Joined:
    Jun 13, 2016
    Location:
    Brazil
    #2
    I don't know what this part of the backplane really does, it's not PCIe AUX Power related anyway, so I can't tell why it failed, but this capacitor failure is very common with tantalum ones and not so much with ceramic types.

    Over current and shorts are a common cause of explosive failure for ceramic capacitors, you should check your PSU before anything.
     
  3. macguru9999, Apr 28, 2019
    Last edited: Apr 28, 2019

    macguru9999 thread starter macrumors regular

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    Aug 9, 2006
    #3
    Is there any guide online to testing a mac pro power supply ? My fear is that I will connect up the new backplane and blow it as well ....
    My experience tells me that a short on the backplane caused by component failure is the most likely cause, but it would still be nice to take out the power supply connect to mains power, turn it on and verify the voltages are within specs.
     
  4. macguru9999 thread starter macrumors regular

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    Aug 9, 2006
    #4
    I may as well do the pixlas mod on the power supply whilst I am testing it ....
     
  5. startergo macrumors 6502a

    startergo

    Joined:
    Sep 20, 2018
    #5
    I would recommend Pixlas 4.1 Mac Pro mod pixlas mode
    for various reasons, one of which is monitoring power draw
     
  6. krakman macrumors regular

    Joined:
    Dec 3, 2009
    #6
    I remember finding something on google/youtube... some non mac user used a MAC PRO psu for his test bench because it was rated for 900W...the video shoed the pin outs and voltages. the thick wires should be 12 V and then there was some talk about the matrix of smaller wires....
     
  7. kohlson macrumors 68000

    Joined:
    Apr 23, 2010
    #7
    I suggest the 2010 Mac Pro Technician's Guide, which can provide some pretty good insights into diagnosis and repair.
     
  8. macguru9999 thread starter macrumors regular

    Joined:
    Aug 9, 2006
    #8
    Yes, that guide helps with the backplane board replacement , I already have a copy, but does anyone have an electronic schematic (circuit diagram) of the 5,1 like the kind Lewis Rossman uses with Open Board View software ??
     
  9. spidertnt macrumors member

    Joined:
    Aug 11, 2014
    #9
    Not available for that model ....are you thinking of trying to repair it ?
     
  10. macguru9999 thread starter macrumors regular

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    Aug 9, 2006
    #10
    No, not when I have bought another backplane. I just wanted to know what CE 500-501-502 actually did....
     
  11. macguru9999 thread starter macrumors regular

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    Aug 9, 2006
    #11
    UPDATE: So I ordered another Mac Pro 5,1 backplane, its a mid 2010, and pulled down the machine and reassembled it fully. It appears to all be working perfectly. The part was from usedmacs in California, $150usd , but postage was quite expensive as I live in Sydney.

    In the meantime I saw a mid 2012 model on ebay for a good price so I moved all my cards and drives over to that, so now I have 3 of these machines :) I am not sure what if any advantages the mid 2012 offers over the 2010 model but its just gratifying seeing "mid 2012" in about this mac. I have always read that there is no functional difference ....
     
  12. tsialex, May 10, 2019
    Last edited: May 10, 2019

    tsialex macrumors 601

    tsialex

    Joined:
    Jun 13, 2016
    Location:
    Brazil
    #12
    Backplane and CPU trays are identical.

    Apple added one more digit to the system serial number for 2012 Macs, so you have 11 digits SSN with mid-2010 and a 12 digits one with mid-2012.

    Another thing of note, Apple used Xeons with little faster clock with mid-2012 compared the mid-2010 equivalent models, useless if you are upgrading the Xeon processors anyway.
     
  13. macguru9999 thread starter macrumors regular

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    Aug 9, 2006
    #13
    Yes, I moved my CPU tray across as well because it has an upgraded hex core 3.46 cpu. No problems there ...
     

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12 April 27, 2019