Brother MFC-3340CN Service Manual page 309

After replacing the main PCB with the one used for other machines
After the installation procedure of the printer driver, proceed to the firmware loading operation.
If the printer driver has been installed so that you start from loading firmware, unplug the power
cord from the electrical outlet, and then plug it into an electrical outlet while holding down the 5
key.
NOTE: Never unplug the machine's or PC's power cord or the USB cable during loading.
Make sure that the machine is connected with your PC using a USB cable.
(1) Run "FILEDG32.exe."
The Filedrgs window will appear as shown below.
(2) Drag and drop the firmware (e.g., LZ0023_A.upd) onto the BHL2-Maintenance Printer icon in
the Filedrgs window shown above.
NOTE: Use a firmware file after extracting. It is a self-extracting file having the
extension .exe. Double-click the exe file to extract it.
NOTE: If the main PCB isn't new or blank, use the file having the extension. upd. It prevents
from writing the wrong program which the PCB doesn't accept.
When loading operation starts, the machine beeps intermittently. After approx. 2 to 5 minutes,
loading operation is complete and the machine automatically reboots and returns to the standby
state.
(3) Press the * and # keys at the same time when the machine is on standby. The firmware version
appears on the LCD.
In this example, if "A0307252244:CF30" appears, it means that the loading operation has been
successfully finished.
(4) If loading operation finishes abnormally, turn the machine off and on. The machine
automatically enters the load mode and emits a large beep. Perform the loading procedure
above again.
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