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Assuming you did not damage anything during the MagSafe board replacement - you might want to open it up again and make sure you did not forget to attach anything - like the cable connecting the keyboard assembly to the main board.

The keyboard cable is a bit tricky to keep connected while assembly and I know for sure the Mac won't boot if the cable is disconnected or loose.
 
Assuming you did not damage anything during the MagSafe board replacement - you might want to open it up again and make sure you did not forget to attach anything - like the cable connecting the keyboard assembly to the main board.

The keyboard cable is a bit tricky to keep connected while assembly and I know for sure the Mac won't boot if the cable is disconnected or loose.

Yeah I took it apart to make sure that was connected also and it is/was because that cable is for power also
 
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