Disconnect power supply, take out battery and press power button for 15 seconds to discharge any power on the motherboard.
Disassemble:
[guide|106685]
Take out the coin shaped CMOS battery (bottom right in photo shown above) for about 30 seconds. Put back in clip.
Reassemble laptop but do not reinsert main battery.
Try turning on the laptop with just the charger plugged in. Does it boot up?
If so now unplug charger put battery back in. Turn it on. Does it boot up?
If yes you are good to go.