No Power The iMac G will not turn on

  1. Refer to the iMac G5 Repair Extension Program for video and power issues mentioned at the beginning of this chapter.
  2. Verify power outlet is good. Plug a different device into the socket to ensure there is power, or plug the iMac G5 into another outlet.
  3. Check the power cord. Use a known good power cord.
  4. Check the connection of the power cord on both ends. Verify that the plug is securely plugged into both the AC outlet and back of the computer.
  5. Remove keyboard, mouse, and other peripherals such as speakers. Try starting up the computer with these devices removed.
  6. Remove the back cover to access the diagnostic LEDs on the main logic board. See "Diagnostic LEDs" in this chapter for complete instructions on this procedure.
  7. Locate LEDs 1 through 4 above the large white arrow in the middle of the main logic board (near the fan cover).
Imac Mid 2007 Diagnostic Led

8. Plug the power cord into the iMac G5 and into the AC outlet. Check to see if LED #1 is On or Off.

  • LED #1 is On. This indicates that the power supply is getting good power from the AC outlet. Go to step 8.
  • LED #1 is Off. This indicates that your power supply should be replaced. Order and install the power supply for your computer.

9. Turn the computer on by using the internal power button. With your finger, or with the nylon probe tool, press the small, metal button. Go on to the next step.

10. Does the computer start up normally after pressing the internal power button?

  • Yes: Press and hold the power button until the computer powers off.
  • Unplug the power cord from the iMac, and reinstall the back cover.
  • Return the computer to the upright position.
  • Plug the computer back in, and press the power button to turn on the computer.
  • Make sure the computer is starting up properly. If the computer will ONLY start up from the internal power but will not power on from the power button on the back cover, the power button on the back cover may be faulty. Go to step 13.
  • No: Press the SMU reset button to reset system power management. The SMU is the small metal button (shown below) located below the internal power button.
Smu Power Button

11. After pressing the SMU button, press the internal power button again. Does the computer start up normally now?

Yes: Press and hold the power button until the machine powers off.

  • Unplug the power cord from the iMac, and replace the back cover.
  • Return the computer to the upright position.
  • Plug the in the computer, and press the power button to turn on the computer.
  • Make sure the computer is starting up properly. If the computer will ONLY start up from the internal power but will not power on from the power button on the back cover, this may indicate that the power button on the back cover is faulty. Got to step 13.

No: Go to the next step.

12. Unplug the power from the iMac G5 and remove the internal hard drive and set it aside. Plug in the iMac G5, and using the Internal power button as before, power on the iMac G5. Does the iMac G5 start up now?

Yes: The hard drive needs to be replaced. No: Go to the next step.

13. When pressing the internal power button to power on the computer, does LED #2 come on momentarily, or not at all?

Momentarily: The logic board has detected 12v, but the power supply cannot maintain it. Your power supply needs to be replaced.

Not at all: Your logic board needs to be replaced.

14. If the computer will ONLY start up from the internal power but will not power on from the power button on the back cover, the back cover may need to be replaced. Unplug the computer and remove the back cover. With the back cover removed, plug the power cord back in. Touch and hold an insulated screwdriver to the two contact points shown below:

Note: The picture below shows the contact points on the iMac G5 (20-inch) computer. The contact points are in the same location on the iMac G5 (17-inch) computer.

A1226 Turn Without Power Button

Does your computer start up when holding your screwdriver to these two contact points?

Yes: This shows that the power button switch is working correctly. The back cover should be replaced.

No: This indicates that the power button switch is not working correctly. The logic board should be replaced.

The Ultimate Computer Repair Guide

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Responses

  • robert
    How to start your computer without a power button.?
    7 years ago
  • mandy biermann
    How to turn a macbook on without the power button?
    7 years ago
  • adonay
    How to fix imac 5521 reset?
    6 years ago

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