I have an "early 2011" MacBook Pro 17" that will not power on when the power switch is depressed.    It functioned normally the previous time it was used.   

I'm a PC I/T specialist so I did some troubleshooting.  Here are actions I tried and the results:

1. Pressed power button and no indication button was pressed.
2. Pressed button on side and it indicated battery fully charged.
3. Attached A/C power adapter and LED on connector lit green like it's charging.   
4. Pressed power button - still no indication of any attempt to power on.
5. Reset SMC by pressing left Shift, Control, Option and power switch.  Released all.   Pressed power button - still no indication of any attempt to power on.
6. Held power button down for 15 seconds, released, then pressed once - no change.
7. Disconnected A/C power. 
8. Removed rear cover.
9. Disconnected battery connector from system board.
10. Connected A/C adapter and pressed power button - no change.
11. Disconnected A/C adapter.
12. Plugged battery connector back in to system board.
13. Attached A/C adapter and the system performed a reset and then IPL up and ran normally!!!!!!
14. "Shut down" system and then pressed the power button - would not power back on.  
15. Removed A/C adapter and pressed the power button - still would not power back on.
16. Disconnected A/C adapter, disconnected battery, reconnected battery to system board.  Pressed power button - would not power on.
17. Repeated the procedure which worked previously - disconnected A/C, disconnected battery from system board, connected A/C, press power button (no signs of activity), disconnected A/C, reconnected battery to system board, reconnected A/C and it reset and powered up!!!!   
18. Let system come up and then "rebooted" (instead of shutting down) - it properly rebooted.  
19. Shut down system and then tried to power on -  would not power on.     
20. Bottom line:   There appears to be only procedure that will get the system to boot after it's shut down:   Disconnected A/C, disconnected battery from system board, connected A/C, press power button (no signs of activity), disconnected A/C, reconnected battery to system board, reconnected A/C and it resets and powers up.

Ok, so you MacBook Pro experts out there......     what appears to be the problem and what steps would you recommend I take?    

Thx,

Jeff