After unscrewing the black rectangular box up from the base of the grey frame, locate the small green rectangular light fixture.

Unscrew the one screw from the green rectangle counter clockwise, and set the screw to the side.

Gently lift the green circuit board out of the socket by pulling on the black and white cables.

At the end of the green rectangle is a light-emitting diode (LED). This is what lights up the power button.