Old iMac keeps turning off randomly

Discussion in 'iMac' started by rogefoo, Jan 24, 2017.

  1. rogefoo macrumors newbie

    Joined:
    Oct 29, 2009
    #1
    I have an old (early 2009) iMac that has been running fine up until about a week ago. All of a sudden it will turn off randomly. Just completely shut down. When I turn it back on, it fires up fine... like nothing happened. The shut downs are just a complete shut down, as if someone pulled the power cord from it. It's instantly to a black screen. I don't change anything, press the power button, and it comes back. There don't seem to be any connections between what I'm doing and the machine turning off. Any thoughts on why or how to fix it??
     
  2. DeltaMac macrumors G3

    DeltaMac

    Joined:
    Jul 30, 2003
    Location:
    Delaware
    #2
    Is it really power going off? and not just the display going off (dark)? You would still be able to hear the fans running if it's only the display.
    If power goes off, and you can restart (you hear the boot chime sound after pressing the power button), then probably the power supply is failing.

    There's a set of 3 or 4 LEDs inside that can tell you a little more about what might be happening. You have to remove the front bezel to see them properly.
     
  3. rogefoo thread starter macrumors newbie

    Joined:
    Oct 29, 2009
    #3
    --- Post Merged, Jan 24, 2017 ---
    It is really going off. Black screen, all sounds are gone. What's so strange is that I don't have to wait any amount of time to turn it back on... it just comes back on as if nothing happened. Then it'll do it again a few days later. Bizarre.
     
  4. Richdmoore macrumors 68000

    Richdmoore

    Joined:
    Jul 24, 2007
    Location:
    Troutdale, OR
    #4
    I had something like this happen with a 2007 MacBook. I eventually figured out it was overheating (while converting movies from DVD to m4v via handbrake).

    Two quick schools of thought.

    If you push your computer, is it more likely to turn itself off? It could be an issue like I had with the overheating.

    Are you running any USB powered hard drives or other high power draw devises? Maybe the power supply has become weak and can't support the the power load. You can try to troubleshoot by reducing screen brightness and disconnecting USB drives.

    Good luck.
     
  5. kiwipeso1 Suspended

    kiwipeso1

    Joined:
    Sep 17, 2001
    Location:
    Wellington, New Zealand
    #5
    I had an original iMacG5 which had the problem with capacitors which is basically the same symptoms, auto-off on overheat.
    I would not be surprised if it was that issue with your iMac, as it is fairly old now, and near end of life.
     
  6. padams35 macrumors regular

    Joined:
    Nov 10, 2016
    #6
    I had similar symptoms starting earlier this month with a 2011 iMac, except that for me the random poweroffs seemed to coincide with the slightest plausible electrical flicker. There was even a chance at shutdown when I turned on the overhead lights! Anyway, mine stopped blackscreening after I replaced the surge protector with an EMI/RFI filtering model. Maybe the old power strip was going bad. Maybe the iMacs capacitors couldn't handle line noise anymore. Maybe the SMC reset that occurred while the iMac was unplugged to exchange surge protectors was all that was required.
     
  7. DeltaMac macrumors G3

    DeltaMac

    Joined:
    Jul 30, 2003
    Location:
    Delaware
    #7
    Ah, good point!
    @rogefoo - Have you tried plugging in power cord to another electrical circuit? Another power strip might even be a good fix. Cheaper than other hardware possibilities, too :D

    In my experience, if you have a shutdown because of overheating, it usually will take 10 minutes or more before you will get much response to start up again, maybe longer until hot parts cool down.
     
  8. rogefoo thread starter macrumors newbie

    Joined:
    Oct 29, 2009
    #8
    I'll look into those ideas. I really appreciate the willingness to help. Thank you guys so much!
     

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