Brother mfc-3420c Service Manual page 3

CHAPTER 7 MAINTENANCE MODE
Describes the maintenance mode which is exclusively designed for the purpose of checks, settings
and adjustments using the keys on the control panel.
In the maintenance mode, you can update memory (EEPROM: electrically erasable programmable
read-only memory) contents for optimizing the drive conditions of the print head unit, paper feed
roller or paper ejection roller (if they have been replaced) or for setting the CIS scanner area, for
example. You can also customize the EEPROM according to the shipment destination of the
machine concerned. In addition, you can perform operational checks of the LCD, control panel PCB
or sensors, perform a print test, display the log information or error codes, and modify firmware
switches (WSW).
CHAPTER 8 ERROR INDICATION AND TROUBLESHOOTING
Details error messages and codes that the incorporated self-diagnostic functions display if any error
or malfunction occurs. If any error message appears, refer to this chapter to find which components
should be checked or replaced.
The latter half of this chapter provides sample problems that could occur in the main sections of the
machine and related troubleshooting procedures. This will help service personnel pinpoint and repair
defective components.
Appendix 1 Serial Numbering System
Shows the location of serial number labels put on some parts and lists the coding information
pertaining to the serial numbers.
Appendix 2 Firmware Installation
Provides instructions on how to update firmware stored in the flash ROM on the main PCB of the
facsimile machine from the host PC. No hardware replacement is required for updating.
Control programs of the facsimile machine are stored in the flash ROM on the main PCB. The
updating procedure is required also if the main PCB has been replaced since a new PCB supplied
has no firmware installed.
Appendix 3 Customizing Codes According to Shipping Destination
Lists the customizing codes for the various preferences exclusively designed for each destination (e.g.
language). Those codes are stored in the memory (EEPROM) mounted on the driver PCB. If the
driver PCB is replaced with a new one, therefore, you will need to set the proper customizing codes
with the machine in the maintenance mode.
Appendix 4 Firmware Switches (WSW)
Describes the functions of the firmware switches, which may be divided into two groups: one is for
customizing preferences designed for the shipping destination (as described in Appendix 3) and the
other is for modifying preferences that match the machine to the environmental conditions. Use the
latter group if the machine malfunctions due to mismatching.
Appendix 5 Wiring Diagram
Provides the wiring diagram that helps you understand the connections between PCBs.
Appendix 6 Circuit Diagrams
Provides the circuit diagrams of the MJ PCB (MFC3820CN), NCU PCB (MFC3420C), and power
supply PCB.
This manual describes the models and their versions destined for major countries. The specifications and
functions are subject to change depending upon each destination.
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