4,1 Mac Pro Won't Power On after Sudden Shutdown

Discussion in 'Mac Pro' started by msh, Sep 27, 2018.

  1. msh macrumors 6502

    Joined:
    Jun 13, 2009
    Location:
    SoCal
    #1
    Machine suddenly shutoff and now won't power on.

    Followed steps in tech manual; red LEDs flash when power connected and STBY yellow LED lights when diagnostic button pushed. Nevertheless, I replaced the power supply and it did power up and boot normally and stayed on for about 8 hours before I did a manual normal shutdown. Restarted the next morning normally then another abrupt unattended shutdown while idle after about an hour. Now won't start at all.

    I have taken it down to almost (everything except removing the CPU from its socket) a minimal configuration per the manual and still can't start it even from the jumper pads on the back plane. So it must be the backplane or the CPU tray, right? I am guessing the backplane board as I remember Apple replacing that during the 4th year of ownership.

    Is it worth replacing the backplane in this thing or just getting a used 2010 for about $500? Will the 4,1 2 x 16gb 1066mhz dimms work in a 2010? It is a pity to trash this machine as the chassis alone is such a beautiful and well made thing.
     
  2. MIKX macrumors 6502a

    MIKX

    Joined:
    Dec 16, 2004
    Location:
    Japan
    #2
    I recently had the same problem .. . but after removing and thoroughly de-dusting the PSU I got CPU A working.

    Did you check the Northbridge heatsink retainer spring rivets on the CPU tray? They break with surprising frequency.

    replacing them and re-newing thermal paste has fixed quite a few cMPs.

    In the end it seems it was a CPU socket problem. I ended up getting a refurbished CPU tray with 32gb ECC RAM.
    works like a charm now.

    Probably just old age.
     
  3. msh thread starter macrumors 6502

    Joined:
    Jun 13, 2009
    Location:
    SoCal
    #3
    That I haven’t tried. Thanks for the suggestions. I will probably take it to a repair shop.
     
  4. msh thread starter macrumors 6502

    Joined:
    Jun 13, 2009
    Location:
    SoCal
    #4
    It was the logic board (backplane). But I will keep in mind the heat sink rivets and new paste for the cpu.
     

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3 September 27, 2018