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SMC Reset on a Late 2006 iMac

8031 Views 13 Replies Latest reply: Dec 22, 2010 8:46 AM by rkaufmann87 RSS
D. Ryder Calculating status...
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Dec 13, 2010 8:24 AM
I have a late 2006 Intel iMac (Model ID iMac5,1) that is having trouble powering on. It will not power on unless I unplug it first, plug it back in and then push the power button immediatly. I tried resetting the SMC according to the procedure here: http://support.apple.com/kb/TS1587 (unplug, hold power button for 5 sec, release, plug in) but that did not solve the problem. I have also seen in the forums and elsewhere in the tech library an SMC reset methodology of unplug, hold power button, plug in, release button.

How can you tell if an SMC reset has occurred? Is there something other than a problematic SMC that could be causing my power-on problem? What is the correct SMC reset procedure for my iMac model?
MacBook, iMac 2007, iBook G4 & others, Mac OS X (10.5.8), 3 AirPort Express home network, Time Capsule
  • rkaufmann87 Level 8 Level 8 (40,585 points)
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    Dec 13, 2010 8:42 AM (in response to D. Ryder)
    Here is the correct procedure for doing an SMC reset on an Intel based iMac.


    _SMC RESET_

    • Shut down the computer.
    • Unplug the computer's power cord and all peripherals.
    • Press and hold the power button for 5 seconds.
    • Release the power button.
    • Attach the computers power cable.
    • Press the power button to turn on the computer.

    You can also try doing a PRAM reset.


    _PRAM RESET_

    • Shut down the computer.
    • Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
    • Turn on the computer.
    • Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
    • Hold the keys down until the computer restarts and you hear the startup sound for the second time.
    • Release the keys.
    iMac and Macbook Pro, Mac OS X (10.6.5), iPhone 3GS Airport Extreme Airport Express
  • WZZZ Level 6 Level 6 (11,880 points)
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    Dec 13, 2010 8:50 AM (in response to D. Ryder)
    How can you tell if an SMC reset has occurred? Is there something other than a problematic SMC that could be causing my power-on problem? What is the correct SMC reset procedure for my iMac model?


    You should see a message about the SMC reset in the logs. Open Console in Utilities and go to system.log. You were using the correct procedure. Might be a good idea to do the reset with all peripherals except keyboard and mouse disconnected.

    You should also do a PRAM reset. At startup hold CMD-Option-P-R together until you hear two more chimes, three total, then let go.

    I'd open Disk Utility in Utilities, highlight the drive and choose Verify. If you get any errors, you will need to boot from the Install Disk and run Disk Repair from there. See "Try Disk Utility"

    http://support.apple.com/kb/TS1417

    You should also run the Hardware Test in Extended. It may be necessary to run it several times before it picks up any errors.

    http://support.apple.com/kb/ht1509
    iMac G3/400 OSX 10.4.11, iMac 21.5" OSX 10.6.5
  • WZZZ Level 6 Level 6 (11,880 points)
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    Dec 14, 2010 3:17 PM (in response to D. Ryder)
    Sorry for the late reply. Now I'm not certain an SMC reset will be logged; before this, I was assuming it would be. In fact, I did an SMC reset last summer and reviewing my secure log where it would normally show up from that long ago, I see nothing. But if you did it according to that procedure, then I don't see why it wouldn't have taken effect.

    Have you tried the other suggestions above?
    iMac G3/400 OSX 10.4.11, iMac 21.5" OSX 10.6.5
  • WZZZ Level 6 Level 6 (11,880 points)
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    Dec 16, 2010 7:08 PM (in response to D. Ryder)
    Tried running the Hardware Test?
    iMac G3/400 OSX 10.4.11, iMac 21.5" OSX 10.6.5
  • den.thed Level 7 Level 7 (23,325 points)
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    Dec 16, 2010 7:12 PM (in response to D. Ryder)
    Question is which fan there are 3 in an Intel iMac, +(HD, CPU and Optical Drive)+ to check download the iStatPro Widget. > http://www.islayer.com/apps/istatpro/

    Or as WZZZ suggested above run the Apple Hardware Test, because it sounds like you have a faulty or disconnected temperature sensor.
    Early Core Duo - 320GB WD Caviar Blue HDD - 2GB RAM - 21.5 LG Display - iPad -, Mac OS X (10.6.5), - Maxtor FireWire HD's - WD Passport - Nikon - Epson - 80GB Classic - 2GB Nano
  • rkaufmann87 Level 8 Level 8 (40,585 points)
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    Dec 16, 2010 7:12 PM (in response to D. Ryder)
    Reset the SMC once again that should take care of the fan problem. the instructions for an iMac are:




    _SMC RESET_

    • Shut down the computer.
    • Unplug the computer's power cord and all peripherals.
    • Press and hold the power button for 5 seconds.
    • Release the power button.
    • Attach the computers power cable.
    • Press the power button to turn on the computer.
    iMac and Macbook Pro, Mac OS X (10.6.5), iPhone 3GS Airport Extreme Airport Express
  • WZZZ Level 6 Level 6 (11,880 points)
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    Dec 17, 2010 5:27 AM (in response to D. Ryder)
    isn't the SMC powered by a battery? Is it possible the battery has died?


    I don't think the SMC is but the PRAM is. There is a PRAM battery; it's a commonly available CR2032 Lithium button battery and its lifetime is around five years. It might be weak or dying. But I don't know if it directly controls the fan behavior. It might be related more to your initial question concerning erratic power on. This article lists what it does control.

    http://support.apple.com/kb/ht1379

    Not sure if this is your model, but just to give you an idea what might be involved in replacing it.

    http://www.ifixit.com/Guide/Repair/Installing-iMac-Intel-20-Inch-EMC-2105-and-21 18-PRAM-Battery/1082/4

    If it's just the CPU fan, it might be a bad sensor, but the Hardware Test, since you ran that 3 times, should have reported that. If you don't already have it or something like it (and you probably do, since you know it's only the CPU fan) I'd get free iStat Pro, so you can see the temps and fan speeds. Although, you seem to be saying the CPU fan is always running fast, even at startup, so that doesn't sound temperature related.

    http://www.islayer.com/apps/istatpro/

    If you can't get to the bottom of this on your own, I think it might be wise to bring it in to an Apple Store and let them run their diagnostics which are far more sophisticated than the Hardware Test; the Hardware Test might be missing something. I don't think they charge for that, but ask first to be sure.
    iMac G3/400 OSX 10.4.11, iMac 21.5" OSX 10.6.5
  • WZZZ Level 6 Level 6 (11,880 points)
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    Dec 22, 2010 5:42 AM (in response to D. Ryder)
    That's very interesting. Thanks for the feedback.
    iMac G3/400 OS X 10.4.11, iMac 21.5" OS X 10.6.5
  • rkaufmann87 Level 8 Level 8 (40,585 points)
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    Dec 22, 2010 8:46 AM (in response to D. Ryder)
    Glad you got it figured out and thank you for the star.
    iMac and Macbook Pro, Mac OS X (10.6.5), iPhone 3GS Airport Extreme Airport Express

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