MDD overheating

Discussion in 'PowerPC Macs' started by Eugen Mezei, Sep 29, 2015.

  1. Eugen Mezei macrumors member

    Joined:
    Mar 21, 2015
    #1
    Bought an MDD 1,25 GHz singleprocessor.
    It overheats and goes into standby. After a while it awakes by itself or a click of the mouse or kb brings him back. For a while, until it goes to sleep again. I also receive overheating messages in single user mode.

    Opened it up and I dont see the big fan spinning. Is it supposed to rotate only above a certain temperature or all the time?
     
  2. jbarley macrumors 68030

    jbarley

    Joined:
    Jul 1, 2006
    Location:
    Vancouver Island
    #2
    It should be running all the time, it is software controlled and varies from minimum rotation to maximum depending on the temperature.
    Sounds like your system is shutting down from over-temperature to protect itself, just as it is designed to do.
     
  3. Eugen Mezei thread starter macrumors member

    Joined:
    Mar 21, 2015
    #3
    I verified all wires, seems o.k. I can get the fan out and try it on a separate source.
    Where are the temperature sensors located? Maybe they are not connected or somehow wrong. Or is the sensor in the CPU itself?
    Can the fan be replaced by any similar size or is it special?
     
  4. gavinstubbs09 macrumors 65816

    gavinstubbs09

    Joined:
    Feb 17, 2013
    Location:
    NorCal boonies ~~~by Reno sorta
    #4
    The big 120mm fan from what I've seen with both of my MDDs (dual 1GHz, dual 1GHz FW800) both stayed at one constant speed regardless of temperature. I would test the fan and replace it with a Cooler Master sickleflow 120mm fan (I put a green one in mine) and re-paste the processors. That should help with both noise and overheating.

    g4mddgreenfan.jpg
     
  5. jbarley, Sep 29, 2015
    Last edited: Sep 30, 2015

    jbarley macrumors 68030

    jbarley

    Joined:
    Jul 1, 2006
    Location:
    Vancouver Island
    #5
    Gavin, not many are unlucky enough to have two systems with the same fault. The large heatsink fan should be variable as indicated by the third connection wire.
    Sorry bad info I was thinking of something else, it is a 2 wire connector and the fan is controlled with software via AppleFan.kext
     
  6. gavinstubbs09 macrumors 65816

    gavinstubbs09

    Joined:
    Feb 17, 2013
    Location:
    NorCal boonies ~~~by Reno sorta
    #6
    The stock fan in an MDD is a red and black wire, so I'd assume if there was any control over speed it would be through voltage.
     
  7. 128keaton macrumors 68020

    128keaton

    Joined:
    Jan 13, 2013
    #7
    Hmm, are you sure it wasn't PWM? On my QS I put a Corsair 120mm fan at 7.5v (replacing the large, loud fan), removed the metal PSU fan guard and repasted my CPU. Almost silent aside from the darn CPU fan. Lil booger sounds ratty and whiny. I really need to sit down and take a look at my MDD. No idea what the specs are and whatnot. I have one more fan I could use, hopefully it will help my MDD not sound like a jet, which it is notorious for sounding like.
     
  8. jbarley macrumors 68030

    jbarley

    Joined:
    Jul 1, 2006
    Location:
    Vancouver Island
    #8
    You're correct about the 2 wire, although mine is blue+red, I've edited my original misleading post as such.
    Not sure what I was thinking at the time, I apologize. :oops:
     
  9. mikiotty macrumors 6502

    mikiotty

    Joined:
    Mar 15, 2014
    Location:
    Rome, Italy
    #9
    In my particular MDD (Dual 1.25GHz FW800) the fan runs at constant speed until the CPU board reached 57°C. The fan ramps up and cools the CPU down to 55°C, then it ramps back down.
     

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