Power but no video computer begins to start up fan and hard drive spins Caps Lock key lights up when pressed but there is no startup sound or video

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Note: Examine the display carefully. An image may be barely present on the screen, but with no backlight clearly illuminating the image. In this case, the system is working properly except for the backlight. Refer to "No display or dim display" troubleshooting symptom to resolve this issue.

1. Reseat memory cards. Try known-good memory.

If you or the customer do not fully seat the memory, the computer will not start up. See Knowledge Base articles 303083, "Intel-based Mac Power On Self Test RAM error codes'; and 303721: "MacBook: How to install memory."

2. Reset the SMC. See Knowledge Base article 303319, "Resetting MacBook and MacBook Pro System Management Controller (SMC)'! Resetting the SMC means you will also need to reset the date and time (using the Date & Time pane of System Preferences).

Warning: Make sure you do not hold down the "fn" key when resetting the SMC.

  1. Press F2 (with the fn key pressed and not pressed) to increase the screen brightness setting.
  2. Try connecting an external display to check for intact video signal. If external video appears, check the system for any pending software or firmware updates and update accordingly.
  3. Verify that the LVDS cable connection is properly seated to its connector on the logic board and that the cables are not damaged.
  4. Reseat inverter cable.
  5. Replace the display assembly.
  6. Check all cable and flex connections to the logic board. Try restarting.
  7. Replace the logic board.

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    How to change display light on apple imac?
    8 years ago

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