Brother MFC5840CN, MFC5440CN, MFC620CN, MFC425CN, MFC20CN Service Manual

Confidential

FACSIMILE EQUIPMENT

SERVICE MANUAL

MODELS: MFC5840CN

MFC5440CN

i Confidential

Preface

This Service Manual is intended for use by service personnel and details the specifications,
construction, theory of operation, and maintenance for the Brother machines noted on the front cover.
It includes information required for troubleshooting and service--disassembly, reassembly, and
lubrication--so that service personnel will be able to understand equipment function, repair the
equipment in a timely manner and order spare parts as necessary.

To perform appropriate maintenance so that the machine is always in the best possible condition for
the customer, service personnel must adequately understand and apply this manual.

How this manual is organized

This manual is made up of nine chapters and appendices.

CHAPTER 1 PARTS NAMES AND FUNCTIONS

Contains external views and names of components and describes their functions. Information about
the keys on the control panel is included to help you check operation or make adjustments.

CHAPTER 2 SPECIFICATIONS

Lists the specifications of each model, which enables you to make a comparison of different models.

CHAPTER 3 THEORY OF OPERATION

Gives an overview of the scanning and printing mechanisms as well as the sensors, actuators, and
control electronics. It aids in understanding the basic principles of operation as well as locating
defects for troubleshooting.

CHAPTER 4 TRANSFER OF DATA LEFT IN THE MACHINE TO BE SENT FOR REPAIR

Describes how to transfer data left in the machine to be sent for repair. The service personnel should
instruct end users to follow the transfer procedure given in this chapter if the machine at the user site
cannot print received data due to the printing mechanism defective. End users can transfer received
data to another machine to prevent data loss.

CHAPTER 5 DISASSEMBLY/REASSEMBLY AND LUBRICATION

Details procedures for disassembling and reassembling the machine together with related notes. The
disassembly order flow provided enables you to see at a glance the quickest way to get to
component(s) involved.

At the start of a disassembly job, you check a disassembly order flow that guides you through a
shortcut to the object components.

This chapter also covers screw tightening torques and lubrication points to which the specified
lubricants should be applied during reassembly jobs.

CHAPTER 6 ADJUSTMENTS AND UPDATING OF SETTINGS REQUIRED AFTER PARTS

REPLACEMENT

Details adjustments and updating of settings, which are required if the head/carriage unit, main PCB
and some other parts have been replaced.

CHAPTER 7 CLEANING

Provides cleaning procedures not covered by the User's Manual. Before starting any repair work,
clean the machine as it may solve the problem concerned.

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CHAPTER 8 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 head/carriage 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 9 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 or load
firmware to a new main PCB from the host PC.

No hardware replacement is required for updating.

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 main PCB. If the main
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 can 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 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.