Try the following;
1. Remove any connected peripherals.
2. Try known-good power outlet.
3. Try known-good power adapter and power cord.
4. Remove battery.
5. Reset the power manager by pressing the key combination Control-Option-Shift-
power.
Warning: Make sure you do not hold down the "fn" key when resetting the
power manager.
Warning: Resetting the power manager means you will also need to reset the
date and time (using the Date & Time control panel).
6. Reset PRAM (Press the power button, then hold down the Option-Command-P-R
keys until you hear the startup chime at least one additional time after the initial
startup chime).
7. Disconnect internal keyboard completely. Inspect connectors. Restart with keyboard
disconnected.
8. Remove any additional RAM and AirPort Extreme Card.
9. Try known-good DC board.
10. Verify cable connections and check cables for damage.
11. Verify power button is connected properly to logic board, if power button is not
functioning correctly or damaged, replace the top case.
12. Replace logic board.
