iMac (17-inch Mid 2006) starts up to black screen or no video

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An iMac (17-inch Mid 2006) may start up to a black screen (with no video). It may also occur if you have just changed the brightness of the display. If this happens, the computer will sound like it's starting up, but the display stays black. In this case, if you hold down the power key to shut the computer down and then try to start it up again, the situation would not be resolved.

If this occurs, follow the steps below—the first steps are to regain normal operation, and the second set of steps are to prevent the issue from happening again.

Get video back

  1. Shut down the computer by pressing and holding the power button on the back of the iMac until it turns off.
  2. Reset the NVRAM. The computer should display a grey screen, then start normally.

Prevent it from happening again

  1. From the Apple menu, choose Software Update...
  2. Make sure the Mac OS X 10.4.8 system software update is selected, and install it. The update will require that you restart your computer after installing.
    An alternative to Software Update is to download the Update from Apple Software Downloads (

Note: If you choose not to install the Mac OS X 10.4.8 software update, the following steps will also prevent the issue from occurring again:

  1. From the Apple menu, choose System Preferences.
  2. Choose the Displays pane of System Preferences.
  3. Temporarily select a resolution other than the 1440 x 900 native resolution.
  4. Switch back to your preferred resolution and close System Preferences.
Published Date: Oct 7, 2016