iMac randomly shut down and won't reboot

Discussion in 'iMac' started by summero, Nov 11, 2011.

  1. summero, Nov 11, 2011
    Last edited: Nov 11, 2011

    summero macrumors regular

    summero

    Joined:
    Mar 13, 2007
    Location:
    San Diego, CA
    #1
    Last night my iMac i3 randomly shut down while I was watching a YouTube video. I tried rebooting and nothing. I left the iMac unplugged all night and this morning I was excited when I plugged it back in and heard the chime. It made it to the desktop, however, it wasn't long until it randomly shut down again. I tried resetting the SMC and get nothing. I tried another time and it booted up and stayed on a little while longer. I began browsing the web and it shut down. Whenever I press the power button, it sounds like the iMac is booting up, but it just doesn't. Is there anything else I can try doing? Or should I just take it in to the Genius Bar?

    Edit: I booted it up again, but this time the fans are blasting.
     
  2. derbothaus macrumors 601

    derbothaus

    Joined:
    Jul 17, 2010
    #2
    So do you get the cog wheel spinning forever? A black screen, a blue screen? No backlight, nothing? Why does no one give sufficient details for a prognosis? Every little detail matters. I would initially think you should repair the Disk with your OS restore discs or repair partition if on 10.7.
     
  3. 666sheep macrumors 68040

    666sheep

    Joined:
    Dec 7, 2009
    Location:
    Poland
    #3
    What for? It does not help for hardware problems and OP has one for sure.

    OP: do you have warranty/Apple Care?
    If so - take it to the Genius Bar - under warranty it's their problem.
    If not - see if all fans are running - maybe one has failed and shut downs are caused by overheathing. iStat is the right tool for this purpose.
    If you have original Install Discs (with 10.6) run hardware test in extended mode.
    Post results.
     
  4. summero thread starter macrumors regular

    summero

    Joined:
    Mar 13, 2007
    Location:
    San Diego, CA
    #4
    Hey guys, thanks for the reply. I had a black screen. I tried resetting the SMC again and it worked. Things are running fine as of right now. Let's hope it stays this way. If not, I'll head to the Genius Bar. Unfortunately I'm not under warranty anymore and I don't have Apple Care.
     
  5. 666sheep macrumors 68040

    666sheep

    Joined:
    Dec 7, 2009
    Location:
    Poland
  6. derbothaus macrumors 601

    derbothaus

    Joined:
    Jul 17, 2010
    #6
    For the REAL placebo effect:)

    Not for sure.
    If his cog wheel was just spinning and spinning it would be fixable with a directory replacement in about 15-20 min. If booting past blue screen then crash it could be memory or graphics card. He never said in what state the "it sounds like the iMac is booting up, but it just doesn't" meant. He has answered "Black screen" so yes a HW test is in order even though he is back up and running with an SMC reset.
    But the test probably wont find anything. As useful as SMART.
     
  7. 666sheep macrumors 68040

    666sheep

    Joined:
    Dec 7, 2009
    Location:
    Poland
    #7
    Not exactly. If dead fan or temp sensor is the culprit AHT will detect it.

    The REAL REAL placebo effect is Repair Permissions :p
     
  8. Detrius, Nov 12, 2011
    Last edited: Nov 12, 2011

    Detrius macrumors 68000

    Joined:
    Sep 10, 2008
    Location:
    Asheville, NC
    #8
    I refer to "Repair Permissions" as superstition, but placebo is accurate, too. Repairing the directory structure will not resolve anything. It's clear from the OP that the machine would not chime.

    Here's what's potentially useful: Check the Console for "Previous Shutdown Cause". Check for every time it shut down on you. Anything negative is likely a problem on an iMac (-60 on a laptop just means the battery died).


    Also, SMART is far more useful than you think. What makes people think it's useless is that people and programs are looking at it not knowing what it means, and therefore, programs are telling you that your drive is fine, even though the actual SMART data plainly says it's not (because the manufacturer doesn't want to replace a drive every time it gets bad blocks). The thresholds are intended to tell you whether catastrophic drive failure is imminent within the next 24 hours. It still has info telling you that the drive is acting up in a less severe manner.


    Okay... you talked me into it. Here's a little tool I've been working on for a while that I use to find potential issues in log files. I've attached it in double-clickable format. The included copy of smartctl was built on a 10.7 machine, and therefore, I'd expect it not to work on 10.6 or older. Don't panic; every machine has errors. In reference to the OP, the relevant info will look somewhat like this:


    Code:
    Summary of shutdowns and sleeps encountered
    shutdown: count	: description
    5	: 6	: (normal shutdown or sleep)
    3	: 2	: (normal restart or power button forced shutdown.  Expected normal behavior)
    0	: 2	: (battery/power disconnected.  Expected normal behavior)
    -128	: 3	: [COLOR="Yellow"](not known.  Did it boot from a different OS?  Potentially normal behavior)[/COLOR]
    

    The script will check the SMART status and tell you if there are any pending sectors, reallocated sectors, or errors in the drive's own internal SMART log. A drive that doesn't know it's bad will look like this:

    Code:
    ##########################################################################
    ####################### Checking SMART Status of Drives ##################
    ##########################################################################
    
    
    smartctl 5.42 2011-10-20 r3458 [x86_64-apple-darwin11.2.0] (local build)
    Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net
    
    === START OF READ SMART DATA SECTION ===
    SMART overall-health self-assessment test result: PASSED
    
    EDIT: Oh, and it will check all attached SMART-capable drives, but it only shows success for the first drive. It will notify you if any other internal drives have potentially bad SMART status.


    The source code is here:
    https://github.com/whschultz/Diag
     

    Attached Files:

  9. derbothaus macrumors 601

    derbothaus

    Joined:
    Jul 17, 2010
    #9
    So true.

    And thanks for the extra SMART info and app Detrius. Can always use more tools.
     

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