Red light showing from processor/memory board

Discussion in 'Mac Pro' started by eyeangle, Mar 21, 2014.

  1. eyeangle macrumors regular

    eyeangle

    Joined:
    Jan 2, 2014
    Location:
    Melbourne, Australia
    #1
    I searched this but found different people say different things. I recently had my logic board replaced by a mac technician and now a red LED light is always on next to the processor. Even when the Mac is turned off.
    IMG_0485.JPG
    The memory seems to be alright showing all 24 GB in About This Mac and the mac runs properly it's just this red light wasn't on before the logic board was replaced.
     
  2. WildBB macrumors member

    WildBB

    Joined:
    Mar 13, 2014
    Location:
    Pandora
    #2
    In my experience on prior Macs, if the red lights on the motherboard stay on, it indicates a problem/failure/error/temp issue...etc... Not sure about the newer model, but I am guessing it follows suit.

    Why don't you return it to the Mac tech who worked on it and ask him to troubleshoot. I think it is like having your engine light come on in your car... it could be quite a few different things.
     
  3. APlus84 macrumors member

    APlus84

    Joined:
    Sep 13, 2009
    Location:
    Hawaii
    #3
    Occasional Light

    I get an occasional (infrequent) blinking of this same light. Today it was when I was making an MKV with HandBrake. Handbrake does like to use the processor.

    Mac seems to work fine.

    Service on Molokai is not an option so any ideas would be appreciated.
     
  4. mikeboss macrumors 65816

    mikeboss

    Joined:
    Aug 13, 2009
    Location:
    switzerland
    #4
    excerpt from the service manual:

    Processor Diagnostic LEDs
    The dual-processor board and single-processor board include a diagnostic LED for each processor. The following illustrations show the location of each LED and its associated processor. These error LEDs are normally off. A red illuminated LED indicates the associated processor may be missing or in overtemp state (PROCHOT).
     
  5. APlus84 macrumors member

    APlus84

    Joined:
    Sep 13, 2009
    Location:
    Hawaii
    #5
    Thanks.

    Hopefully, it is just a little cooling. It is dusty here as we don't run A/C at $0.46KWh. I'll check it out.
     
  6. martyr macrumors newbie

    martyr

    Joined:
    Jun 19, 2007
    #6

    Hey There,

    I'm getting the same flashing light on one of my dual CPUs. Typically only happens during a stress test like Geekbench. I'm assuming it is temperature related.

    Curious if you investigated it further, etc.

    Thanks!

    Josh
     
  7. BillyBobBongo macrumors 68020

    BillyBobBongo

    Joined:
    Jun 21, 2007
    Location:
    On The Interweb Thingy!
    #7
    Had this not that long ago on my Mac Pro, believe it or not changing the cable to the monitor fixed it.

    Pull all the cables out the back of the Mac, turn it on, and see if the light turns on.
     
  8. MIKX macrumors 6502a

    MIKX

    Joined:
    Dec 16, 2004
    Location:
    Japan
    #8
    Check your Northbridge Spring Retainer Rivets on the processor tray .. and yes. . de-dust the heatsinks.
     
  9. tsialex macrumors 68030

    tsialex

    Joined:
    Jun 13, 2016
    Location:
    Brazil
    #9
    This red led on my Mac Pro usually shows memory over temperature. Usually happens in hot days when I’m using RAMDisk to compile things.
     
  10. martyr macrumors newbie

    martyr

    Joined:
    Jun 19, 2007
    #10
    Interesting. It's definitely not hot in the room here - currently snowing in Calgary - but take a look at the "Relative to ProcHot" reading, along with all the other sensor readings and let me know what you think.

    [​IMG]

    I'm thinking I might have to re-apply some thermal paste and may be tighten the heatsinks. Running two X5690s.

    Thanks for your help, btw!
     
  11. tsialex macrumors 68030

    tsialex

    Joined:
    Jun 13, 2016
    Location:
    Brazil
    #11
    Really weird. You definitively have something wrong.
     
  12. martyr macrumors newbie

    martyr

    Joined:
    Jun 19, 2007
    #12
    Okay, that's what I was thinking. I've been reading a lot about the Northbridge heatsink retainer clips breaking on these. The thermal paste might need replacing on the CPUs. And the CPU heatsinks might not be seated properly.

    Bought this used by somebody that knows what they were doing but I haven't lifted the CPUs yet. Dealing with one issue at a time. Haha.

    I'll try and remember to post back here and thanks for all the continued help.
     
  13. expede macrumors regular

    expede

    Joined:
    Jan 15, 2018
    Location:
    Sweden
    #13
    Hi!
    This is what the "Apple Technician Guide say;

    "These error LEDs are normally off. A red illuminated LED indicates the associated preocessor may be missing or in overtemp state (PRICHOT).


    [​IMG]

    Best regards

    EDIT: Saw that this an very old question. Sorry. He, he!! The question is very old.
    /Per
     
  14. martyr macrumors newbie

    martyr

    Joined:
    Jun 19, 2007
    #14
    I wanted to follow-up here.

    I removed the CPU B heatsink and re-applied some $20 Cooler Master Nano thermal paste (the good stuff!) The good news is that this completely fixed the flashing red light. The value of "Relative to ProcHot" normalized and my fans started acting as normal as well.

    My thinking is that there was not enough thermal paste, causing the processor to keep bumping up against the processor's limit. This, in turn, caused the motherboard to go into emergency mode and maxed out the intake and exhaust fans, even during idle after the temperatures had calmed down.

    Fixing the red light and running the fans normally were huge wins for daily use of this bad boy. It's so quiet now. Just the GTX 980 Ti humming away that I gotta fix. I think I saw some additional Geekbench performance with the new thermal paste as well. Btw, I re-applied the same thermal compound to CPU A - I didn't want to neglect her.

    So, that problem is solved.

    Next what happened was that Slot 6 of my RAM was causing issues, not being recognized and showing the red LED on the motherboard. I ended up buying a new stick from OWC to replace the one in question but that didn't work either. I removed the CPU B again to see if I messed something up and I found that one of the gold "caps" on the CPU had fallen off and was now lodged in the base pins. Pictures below.

    I managed to remove the piece lodged in the base pins but couldn't get the base pins realigned without a magnifying glass and a sewing needle. But, it still boots and gets a respectable 23000 on Geekbench so I put 3 sticks of 16GB in Slots 1, 2, 3 and 5. Packaged it up. And called it a day.

    For now...

    IMG_0169.jpg IMG_0170.jpg IMG_0164.jpg IMG_0155.jpg IMG_0156.jpg
     
  15. orph macrumors 68000

    orph

    Joined:
    Dec 12, 2005
    Location:
    UK

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