Brother mfc-3420c Service Manual page 2

Preface
This Service Manual is intended for use by service personnel and details the specifications,
construction, theory of operation, and maintenance for the Brother facsimile equipment 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 facsimile equipment 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 eight 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
Summarizes the scanner and printing mechanisms and control electronics. It also provides
information about sensors and their actuators. This chapter helps you to understand the operating
principles and isolate the source of a problem (troubleshooting).
CHAPTER 4 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 5 ADJUSTMENTS AND UPDATING OF SETTINGS REQUIRED AFTER PARTS
REPLACEMENT
Details adjustments and updating of settings, which are required if the print head unit, carriage,
PCBs and some other parts have been replaced. Settings are stored in the EEPROM on the driver
PCB.
CHAPTER 6 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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