Brother HL-3400CN Series User Manual page 215

USER'S GUIDE
5-58
5. Press the DIMM straight into the slot (press firmly). Make sure
the locks on each side of the DIMM snap inwards into place.
(To remove a DIMM, the locks must be released.)
Notes
When you install less than two DIMMs, be sure to install them in the
order Slot 1and then Slot2.
When you install different capacities of DIMMs, be sure to install the
larger capacity DIMM in Slot 1 and the smaller capacity DIMM in
Slot 2.
6. Refit the main controller board into the printer by sliding it into
the guide rails.
Fig. 5-75 Refit the Main Controller board
7. Secure the main controller board with the two screws.
8. Reconnect the printer cable from your computer. Plug the power cord
into the AC outlet and turn on the printer.
9. To check whether the DIMM has been installed correctly, you may
perform a Test Print "Print Configuration" that will print the current
memory size.