Brother MFC8440D Service Manual page 5

7/13/2019
3.2.2 For Parallel Interface Cable Users
(For Windows
3.2.3 For Windows NT
3.2.4 For Network Interface Cable Users
(For Windows
3.2.5 For USB Interface Cable Users (For Mac
3.2.6 For USB Interface Cable Users (For Mac
3.2.7 For Network Interface Cable Users (For Mac
3.2.8 For Network Interface Cable Users (For Mac
CHAPTER 3 THEORY OF OPERATION................................................. 3-1
1. ELECTRONICS ...................................................................................................... 3-1
1.1 General Block Diagram ....................................................................................................3-1
1.2 Main PCB Block Diagram .................................................................................................3-2
1.3 Main PCB .........................................................................................................................3-3
1.3.1 CPU.....................................................................................................................................3-3
1.3.2 USB.....................................................................................................................................3-3
1.3.3 IEEE 1284 ........................................................................................................................... 3-4
1.3.4 ROM....................................................................................................................................3-4
1.3.5 Flash ROM .......................................................................................................................... 3-5
1.3.6 SDRAM ............................................................................................................................... 3-5
1.3.7 Optional RAM ...................................................................................................................... 3-6
1.3.8 EEPROM.............................................................................................................................3-7
1.3.9 Reset circuit ........................................................................................................................ 3-7
1.3.10 Engine I/O ........................................................................................................................... 3-7
1.3.11 Panel I/O ............................................................................................................................. 3-7
1.3.12 Video I/O ............................................................................................................................. 3-8
1.3.13 Scanner control ................................................................................................................... 3-8
1.3.14 Power supply.......................................................................................................................3-9
1.4 Engine PCB ....................................................................................................................3-10
1.5 Power Supply..................................................................................................................3-11
1.5.1 Low-voltage power supply .................................................................................................3-11
1.5.2 High-voltage power supply ................................................................................................3-12
2. MECHANICS ........................................................................................................ 3-13
2.1 Overview of Printing Mechanism ....................................................................................3-13
2.2 Scanner Mechanism.......................................................................................................3-14
2.3 Paper Transfer ...............................................................................................................3-15
2.3.1 Paper supply ..................................................................................................................... 3-15
2.3.2 Paper registration .............................................................................................................. 3-15
2.3.3 Paper eject ........................................................................................................................ 3-16
2.3.4 Duplex printing .................................................................................................................. 3-16
2.4 Sensors ..........................................................................................................................3-17
2.4.1 Cover sensors ................................................................................................................... 3-17
2.4.2 Toner sensors ................................................................................................................... 3-17
2.4.3 Cassette sensor / Paper empty sensor ............................................................................. 3-18
2.4.4 Paper eject sensor ............................................................................................................ 3-18
2.4.5 MP-PE sensor ................................................................................................................... 3-19
2.4.6 Document cover sensor ....................................................................................................3-19
2.4.7 Document front sensor / Document rear sensor ............................................................... 3-20
2.4.8 DX-sensor PCB ASSY....................................................................................................... 3-20
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Brother 8840D Service Manual
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95/98/98SE/Me/2000 Professional/XP) ................................................... 2-13
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Workstation Version 4.0 Users............................................................2-18
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95/98/98SE/Me/NT/2000 Professional/XP)..............................................2-20
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OS 8.6 to 9.2 Users)...................................... 2-23
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OS X 10.1/10.2.1 or greater Users)............... 2-24
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MFC-8440/8840D/8840DN, DCP-8040/8045D/8045DN
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OS 8.6 to 9.2 Users) ................................2-25
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OS X 10.1/10.2.1 or greater Users) .........2-26
SERVICE MANUAL
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