Aging Asus g73sw-xt1 Laptop:

After having disassembled the unit, I made many repairs including
resoldering the AC-Adapter pin. Then I reinstalled the mobo and fans in
the bottom tray. Connected the power and pressed the ON button: nothing.
I had expected the fans to start moving. There isn't a single LED on
this board to show anything. For now the question is still relatively
simple, when should I see something that says the board is 'working'?

TIA