CHIME!
Not saying Mayer is wrong but a couple things worth a try
# Disconnect keyboard completely. Inspect connectors. Restart with keyboard disconnected.
# Try powering up without the battery installed If it boots, replace battery connector cable.
# Reset the power manager.
'''Resetting the Power Manager (SMC)'''
Disconnect the power adapter and remove the main battery.
Hold the power button down for five seconds, then release.
Install the main battery and connect the power adapter.
Press the power button to restart the computer.
There is a whole page of troubleshooting in the manual that '''may''' assist you to progress further