Backlight inverter board for the A1138 dual layer superdrive version (1440x960 screen) of the 1.67GHz 15" Aluminium PowerBook G4 only. This inverter will not work with any earlier versions of the PowerBook. The inverter board powers the backlight tube within the LCD display. If the backlight on your PowerBook is not illuminating but you can see a faint dark image then the inverter board is a likely culprit. These symptoms can also be caused by a failed backlight tube, a failed inverter cable or a faulty logic board.