Brother HL-3400CN - Manual (Page 211)

USER’S GUIDE
5-54
2. Unscrew the two screws securing the rear plate of the main controller
board. Remove the screws and pull out the main controller board.
Fig. 5-68 Unscrew the two screws
3. Remove the Lock Bar securing the NC-3100h
Fig. 5-69 Removing the Lock Bar