Acer AT1945 Service Manual page 27

(Fig 4)
Remove the main board, power Board, IR board and key board.
1. Remove the rear cover, then the main board .power board, ir board and key board show as below. (Fig 5-6)
2. Remove the twelve screws marked in red to remove power board, IR board and main board. (Fig 9)
3. Remove all the connecting wires marked in green for these boards.
(Fig 5)