The board is held in place with a small Phillips screw.

Ater removing the screw the board can be gently extricated from the tube. The white plastic disc to the right of the screw needs to be pushed to the right to free up the board.

Note the red and black wires. This connector inserts laterally. The wires go to the battery receptor in the middle of the tube.

The screw is in two parts, a phillips screw goes into a post screw. The top screw holds in the board and the post screw holds the On/Off switch in place.