Mac Pro 4.1 no power

Discussion in 'Mac Pro' started by broink, Apr 19, 2019.

  1. broink macrumors newbie

    Joined:
    Apr 18, 2019
    Location:
    Bucharest, Romania
    #1
    Hello everybody.

    I need some help, if anybody can answer me.

    I recently bought a 2009 Mac Pro 4.1, 2,66 ghz single processor.
    He came with broken PSU, with a pc GPU and no power cord.
    It was really cheap.

    I've tested the first time, put a power cord and push the on button. I've heard the classic DING and nothing else. Second time, it didn't work.

    So, I've acquired from ebay a new PSU, almost identical, the old one was DELTA Part No 614-0435 and the new one is AC BEL Part No 614-0436, same output 980W. I think they are the same:
    [​IMG]

    I've put it in, press the on button, nothing happens.
    I've take it apart, removed everything (HDD, battery, cables, bluetooth) for the minimum configuration test.
    When the power cable is attached, two red lights (OVTMP CPUA / OVTMP CPU B) are on for almost a second. When i take it off, again, the two red lights. When I press the diag button, the (5V STBY) it turns on. This was the first step according to the service manual. So all good, no?

    Second step is to reinstall processor cage with fans and processor board. Do not reinstall processor(s), heatsinks, or memory. Did that, 5V STBY turns on. The manual says: Momentarily jump the SYS_PWR solder pads to turn ON the Mac Pro.

    Well, nothing happens here.

    Expected behavior:
    • Front and rear processor cage fans (and PCIe fan, if installed) should spin slowly
    • One red-colored error LED illuminates on the processor board (next to the memory slots).


    7. Press and hold the DIAG button.
    Expected behavior:
    • PSU PWROK (green), 5V STBY (amber), EFI DONE (green), GPU OK (green) LEDs illuminated
    • No startup tone
    • Front and rear processor cage fans (and PCIe fan, if installed) should spin slowly


    Nothing on pressing the DIAG button, same yellow light from 5V STBY led.
    In the manual, is nothing (or I cannot find it) if this step is failed.

    Anybody have any idea what I should do?
    Is a failure from the logic board or the new PSU ?

    Thank you.
     
  2. macguru9999 macrumors regular

    Joined:
    Aug 9, 2006
    #2
    sounds like you have 2 good power supplies

    probably the backplane board is faulty, it usually is when a 4,1 fails to start
     
  3. Alaska_guy macrumors regular

    Joined:
    Mar 30, 2018
    #3
    Try this... Pull the power supply out completely, plug the power supply into a wall outlet for a minute or so. It should have zero load. Unplug it from the power outlet, put the power supply back in the machine and see if it will power on. Mine was having the same issue and this resolved it for me.
     
  4. Alaska_guy macrumors regular

    Joined:
    Mar 30, 2018
    #4
    Just wanted to report back that I tried to turn my mac on today and it wont do anything again. Still waiting on the power supply. I will report back if this solved the issue in hopes it helps you as well.
     
  5. Alaska_guy macrumors regular

    Joined:
    Mar 30, 2018
    #5
    Installed the replacement power supply and same symptom, completely dead. Imagine the logic board took a dump.
     
  6. macguru9999 macrumors regular

    Joined:
    Aug 9, 2006
    #6
    Backplane board most likely. The swap takes a bit longer but its not too bad, if you can find one at the right price on ebay.
     

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5 April 19, 2019