Brother HL 1240 - B/W Laser Printer Service Manual page 5

4.3 Two Side Printing (Manual Duplexing)............................................................................2-11
4.3.1 To print on both sides of the paper from the paper cassette ............................................ 2-11
4.3.2 To print on both sides of the paper from the manual feed slot.......................................... 2-12
5. CONTROL PANEL OPERATION................................ ................................ ...........2-13
5.1 Ready (Paper) LED Indications ......................................................................................2-13
5.2 Data (Toner) LED Indications .........................................................................................2-14
5.3 Drum LED Indications .....................................................................................................2-14
5.4 Alarm LED Indications ....................................................................................................2-14
5.5 Control Panel Button Operations ....................................................................................2-15
5.6 Other Control Features ...................................................................................................2-15
5.6.1 Sleep mode....................................................................................................................... 2-15
5.6.2 Test print mode ................................................................................................................. 2-16
CHAPTER 3 THEORY OF OPERATION .................................................3-1
1. ELECTRONICS ................................ ................................ ................................ .......3-1
1.1 General Block Diagram.....................................................................................................3-1
1.2 Main PCB Block Diagram .................................................................................................3-3
1.3 Main PCB..........................................................................................................................3-5
1.3.1 ASIC.................................................................................................................................... 3-5
1.3.2 ROM.................................................................................................................................... 3-8
1.3.3 DRAM.................................................................................................................................. 3-9
1.3.4 Optional RAM.................................................................................................................... 3-11
1.3.5 Optional serial I/O ............................................................................................................. 3-12
1.3.6 EEPROM........................................................................................................................... 3-12
1.3.7 Reset circuit ...................................................................................................................... 3-13
1.3.8 Engine I/O ......................................................................................................................... 3-14
1.4 Engine PCB ....................................................................................................................3-14
1.5 Power Supply..................................................................................................................3-15
1.5.1 Low-voltage Power Supply ............................................................................................... 3-15
1.5.2 High-voltage Power Supply............................................................................................... 3-16
2. MECHANICS ................................ ................................ ................................ .........3-17
2.1 Overview of Printing Mechanism ....................................................................................3-17
2.2 Paper Transfer ................................................................................................................3-19
2.2.1 Paper supply ..................................................................................................................... 3-19
2.2.2 Paper registration.............................................................................................................. 3-19
2.2.3 Paper eject........................................................................................................................ 3-20
2.3 Sensors...........................................................................................................................3-20
2.3.1 Cover sensors A and B ..................................................................................................... 3-20
2.3.2 Toner sensor..................................................................................................................... 3-21
2.4 Drum Unit........................................................................................................................3-21
2.4.1 Photosensitive drum ......................................................................................................... 3-21
2.4.2 Primary charger ................................................................................................................ 3-21
2.4.3 Transfer roller.................................................................................................................... 3-21
2.4.5 Cleaner ............................................................................................................................. 3-21
2.5 Toner Cartridge...............................................................................................................3-21
2.6 Print Process...................................................................................................................3-22
2.6.1 Charging ........................................................................................................................... 3-22
iii
TABLE OF CONTENTS