Early Intel iMac keeps shutting down and not powering on

Discussion in 'iMac' started by mattbrewster, Aug 7, 2009.

  1. mattbrewster macrumors newbie

    Joined:
    Aug 6, 2009
    #1
    Hi all,

    I have an early Intel iMac (Core Duo 20") that of late is experiencing problems...

    When I'm using it, it randomly shuts down and refuses to power on until a few minutes have passed.

    When it crashes/shuts down I disconnect all cables for a few minutes, and then try to power up. Sometimes it works straight away, other times I need to try again in a few more minutes.

    When I say "shuts down" I mean the power just goes, no screen, no LED, no noise, everything just dies. When I say "won't power on" I mean I press the power button but nothing happens, no screen, no beeps, no chime, no whirring, nothing.

    Any ideas about what to check first? I personally think it's either (a) overheating or (b) the power supply is knackered or (c) both of the above!

    I've tried a different power cable and also disconnecting all peripherals, no difference.

    Thanks
    Matt
     
  2. ArcspacE macrumors member

    Joined:
    Jul 31, 2009
    #2
    Could be heat.
    How old is your imac?
    Check out the 'HDDs failing' thread below.
     
  3. jmulls macrumors newbie

    Joined:
    Feb 15, 2004
    Location:
    New Jersey
    #3
    Same here

    Same thing happens here, but it restarts. I suspect it is a heat issue since it happens on summer days when we do not have AC on in the house. Annoying.
     
  4. ArcspacE macrumors member

    Joined:
    Jul 31, 2009
  5. mattbrewster thread starter macrumors newbie

    Joined:
    Aug 6, 2009
    #5
    It's an early 2006 iMac Core Duo 20" 250GB.

    i'll install iStat tonight and post back my results.
     
  6. mattbrewster thread starter macrumors newbie

    Joined:
    Aug 6, 2009
    #6
    OK I've installed iStat and have been using the machine for a while now. Temperatures are:
    • Local disk: 29
    • CPU: 36
    • Ambient: 26
    • GPU diode: 45
    • HD bay: 34
    • Mem controller 38
    • Optical drive 28
    Do these look acceptable or are any a problem?

    Thanks
    Matt
     
  7. indg macrumors 6502

    Joined:
    Feb 7, 2007
    #7
    it's not that the gpu temp is high, but due to a flaw in the logic board, the system thinks it's overheating and shuts down. a lot of 2006 intel imacs have this problem, yet apple refuses to acknowledge it. it affects imacs with both Nvidia and ATI GPUs.

    see my reply in another thread:
    http://forums.macrumors.com/showpost.php?p=8256017&postcount=4

    running the apple hardware test will not detect any problems because from the system's point of view, everything is running normally as it should be.
     
  8. killerrobot macrumors 68020

    killerrobot

    Joined:
    Jun 7, 2007
    Location:
    127.0.0.1
    #8
  9. mattbrewster thread starter macrumors newbie

    Joined:
    Aug 6, 2009
    #9
    I've already tried resetting the SMC (i.e. unplugging it for 15 seconds), no dice.

    Does the effectively mean that my £1200 iMac is essentially now an Apple-badged paperweight? Anyone know how much this will cost to fix, or if it's even fixable..?
     
  10. killerrobot macrumors 68020

    killerrobot

    Joined:
    Jun 7, 2007
    Location:
    127.0.0.1
    #10
    If the SMC isn't resetting it, and it isn't always repowering right after that then it seems like you need to take in for a diagnosis. Your temps are fine - the shut off should be around 95C.
    If it's the logic board, you'd be better of buying a new iMac, if it's the power supply it should be much cheaper to fix that.
    Sorry.:(
     
  11. mattbrewster thread starter macrumors newbie

    Joined:
    Aug 6, 2009
    #11
    Thanks for the reply. I'll phone up my local apple shop and book it in for a diagnosis, and my wallet and I will wait patiently for the result...
     
  12. MattMoB macrumors newbie

    Joined:
    Mar 15, 2008
    #12
    Hi Matt, did you ever come to a conclusion on this? i've got the same problem with my 2006 iMac, Just turns itself off.
    I took it into a genius bar just outside London and they flat out refused to help me(wouldn't even attempt to switch it on) as it's a vintage machine. Slightly disappointed with the service i have to say.
    Back to the point though, doing a bit of googling this seems to have been a common fault but i've found no reason or fix so far.
    Any help is greatly appreciated!!!
     
  13. MattMoB macrumors newbie

    Joined:
    Mar 15, 2008

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