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Mike
Mike, Mac Support Specialist
Category: Mac
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Experience:  Apple trained Technician, A+ Certified, 20+ years of Mac support, repairs, training, and consulting
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My iMac shut off during a power outage last night and it wont

Customer Question

My iMac shut off during a power outage last night and it won't turn back on. It isn't making any noise or anything. It's completely unresponsive. I have tried all the trouble shooting things I can find. Unplugging everything from the computer, waiting 30 sec. and trying again. None of it's helping. I think it's a bigger problem, what else could it be?
Submitted: 5 years ago.
Category: Mac
Expert:  Freddy M. replied 5 years ago.
  1. Remove the back cover to access the diagnostic LEDs on the main logic board (see Chapter 4 of your iMac G5 User Manual for instructions on removing the back cover).
  2. With the back cover removed, locate diagnostic LEDs 1 through 4 on the main logic board, shown above the large white arrow in the image below.

  3. Plug the power cord into your iMac G5 and into a working electrical outlet. Check to see if LED 1 is on or off.
    • If LED 1 is on, the power supply is getting power from the electrical outlet. Go to step 8.
    • If LED 1 is off, the computer's power supply should be replaced. Please schedule a service appointment with either an Apple Retail Store or an Apple Authorized Service Provider.
  4. Turn the computer on using the internal power button (press the small, metal button under the fan cover as shown below).

  5. Does the computer start up normally after pressing the internal power button?
    • If yes:
      1. Press and hold the power button until the computer turns off.
      2. Unplug the the power cord from the iMac and replace the back cover.
      3. Return the computer to the upright position.
      4. Plug the power cord back into the computer and press the power button on the back cover to turn it on.
      5. Make sure the computer starts up properly. If the computer won't start up when you press the power button on the back cover but did when you pressed the internal power button, go to step 11.
    • If no: Reset the System Management Unit (SMU) by pressing the SMU button (the small, metal button next to the internal power button, shown below).

      Note: If you're using an iMac G5 (Ambient Light Sensor) computer, your SMU was already reset when you unplugged and replugged the computer. You won't see an SMU reset button to press, and that's OK, as this action has already been done. (If you aren't sure which iMac G5 model you have, click here for help.)

  6. After resetting the SMU, press the internal power button again. Does the computer start up normally now?
    • Yes:
      1. Press and hold the power button until the computer turns off.
      2. Unplug the the power cord from the iMac and replace the back cover.
      3. Return the computer to the upright position.
      4. Plug the power cord back into the computer and press the power button on the back cover to turn it on.
      5. Make sure the computer starts up properly. If the computer won't start up when you press the power button on the back cover but did when you pressed the internal power button, go to step 11.
    • No: Go to step 12.
  7. Unplug the computer and remove the back cover. Plug the power cord back in. Press the internal power button (shown below) to start up the computer. If the computer starts up now, but not when you push the button on the back cover, please contact your local Apple Retail Store or Apple Authorized Service Provider for service.
  8. Press the internal power button (shown below) to start up the computer.


    Does LED 2 come on momentarily, or not at all?

  9. guide
Customer: replied 5 years ago.
This is for a G5 mines an intel will this still work?
Expert:  Freddy M. replied 5 years ago.
Yes this should still work
Customer: replied 5 years ago.
I cant find anything on how to take the back cover of an intel imac off. can you help
Expert:  Freddy M. replied 5 years ago.
is it a mini?
Customer: replied 5 years ago.
its an imac. 20" intel aluminum
Expert:  Freddy M. replied 5 years ago.
Ok I am unfamiliar with that model so I will opt out and send this to someone who is so they can continue with you.
Expert:  Mike replied 5 years ago.
Hi,

Other than all that you tried so far, have you verified there is still power to the outlet it is plugged into?

If all else fails to start it up, then the only other option you have is to take it in to Apple and have it evaluated by them for the problem.

It really sounds like the power outage may have included a brown-out power shortage and that may have fried the power supply.

Mike

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