Brother HL-730PLUS User manual

SERVICE MANUAL
MODEL:HL-720/730/730Plus
R
LASER PRINTER

© Copyright Brother 1996
All rights reserved.
No part of this publication may be reproduced in any form or by any means without permission in
writing from the publisher.
Specifications are subject to change without notice.
Trademarks:
The brother logo is a registered trademark of Brother Industries, Ltd.
Apple,the Apple Logo,and Macintosh are trademarks,registered in the United States and other
countries,and True Type is a trademark of Apple computer, Inc.
Epson is a registered trademark and FX-80 and FX-850 are trademarks of Seiko Epson Corporation.
Hewlett Packard is a registered trademark and HP Laser Jet II, IIP, and IID are trademarks of Hewlett-
Packard Company.
IBM,IBM PC and Proprinter are registered trademarks of International Business Machines
Corporation.
Microsoft and MS-DOS are registered trademarks of Microsoft Corporation.
Windows is a registered trademark of Microsoft Corporation in the U.S. and other countries.

PREFACE
This service manual contains basic information required for after-sales service of the laser printer
(here-after referred to as "this machine" or "the printer"). This information is vital to the service
technical in maintaining the high print quality and performance of the printer.
This service manual covers both HL-720 and HL-730/730Plus.
This manual consists of the following chapters:
CHAPTER I: FEATURES AND SPECIFICATIONS
Features, specifications, etc.
CHAPTER II: THEORY OF OPERATION
Basic operation of the mechanical system, the electrical system and the electrical
circuit, and their timing.
CHAPTER III: DISASSEMBLY AND REASSEMBLY
Procedures of disassembling and reassembling the mechanical system.
CHAPTER IV: TROUBLESHOOTING
Reference values and adjustments, troubleshooting for image defects,
troubleshooting for malfunctions, etc.
APPENDICES: Connection diagrams, PCB circuit diagrams.
Note: There are each captions for HL-720 and HL-730/730Plus to divide this manual according to
the contents. You can fin the captions under the headings. Please pay attention to them On
the other hand, the headings have no captions that means the contents are common to HL-
720 and HL-730/730Plus.
Information in this manual is subject to change due to improvement or re-design of the product. All
relevant information in such cases will be supplied in service information bulletins (Technical
Information).
A thorough understanding of this printer, based on information in this service manual and service
information bulletins, is required for maintaining its quality performance and for fostering the practical
ability to find the cause of problems.

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CONTENTS
CHAPTER I FEATURES AND SPECIFICATIONS....................................................... I-1
1. SYSTEM REQUIREMENTS................................................................................................I-1
2. FEATURES .......................................................................................................................I-1
3. SPECIFICATIONS ..............................................................................................................I-4
3.1 Printing.......................................................................................................................................I-4
3.2 Functions ...................................................................................................................................I-5
3.3 Electrical and Mechanical..........................................................................................................I-6
3.4 Paper Specification....................................................................................................................I-7
3.5 Print Delivery..............................................................................................................................I-7
3.6 Paper .........................................................................................................................................I-7
3.7 Effective Printing Area ...............................................................................................................I-8
4. SAFETY INFORMATION ..................................................................................................I-10
4.1 Laser Safety (110 - 120V Model only))....................................................................................I-10
4.2 CDRH Regulations (110 -120V Model only)............................................................................I-10
4.3 Caution for Laser Product........................................................................................................I-11
CHAPTER II THEORY OF OPERATION .................................................................... II-1
1. ELECTRONICS..................................................................................................................II-1
1.1 General Block Diagram.............................................................................................................II-1
1.2 Main PCB Block Diagram .........................................................................................................II-3
1.3 Main PCB..................................................................................................................................II-5
1.3.1 CPU Core................................................................................................................................. II-5
1.3.2 ASIC......................................................................................................................................... II-7
1.3.3 ROM....................................................................................................................................... II-13
1.3.4 DRAM..................................................................................................................................... II-13
1.3.5 Optional RAM......................................................................................................................... II-15
1.3.6 Optional Serial I/O................................................................................................................. II-16
1.3.7 EEPROM................................................................................................................................ II-16
1.3.8 Reset Circuit........................................................................................................................... II-17
1.3.9 CDCC I/O ............................................................................................................................... II-18
1.3.10 Engine I/O .............................................................................................................................. II-19
1.3.11 Paper Feed Motor Drive Circuit.............................................................................................. II-21
1.4 Panel Sensor PCB..................................................................................................................II-22
1.5 Power Supply..........................................................................................................................II-23
2. MECHANICS....................................................................................................................II-24
2.1 Overview of printing mechanism............................................................................................II-24
2.2 Paper Transfer........................................................................................................................II-25
2.2.1 Paper Supply.......................................................................................................................... II-25
2.2.2 Paper Registration.................................................................................................................. II-25
2.2.3 Paper Eject............................................................................................................................. II-26
2.3 Sensors...................................................................................................................................II-27
2.3.1 Cover Sensor ......................................................................................................................... II-27
2.3.2 Toner Empty Sensor .............................................................................................................. II-27
2.4 Drum Unit................................................................................................................................II-28
2.4.1 Photosensitive Drum.............................................................................................................. II-28
2.4.2 Primary Charger..................................................................................................................... II-28
2.4.3 Developer Roller..................................................................................................................... II-28
2.4.4 Transfer Roller........................................................................................................................ II-28
2.4.5 Cleaner Roller ........................................................................................................................ II-28

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2.4.6Erase lamp ............................................................................................................................II-28
2.5 Print Process..........................................................................................................................II-28
2.5.1Charging.................................................................................................................................II-28
2.5.2Exposure stage......................................................................................................................II-29
2.5.3Developing.............................................................................................................................II-30
2.5.4Transfer..................................................................................................................................II-30
2.5.5Drum Cleaning Stage.............................................................................................................II-31
2.5.6Erasing Stage.........................................................................................................................II-31
CHAPTER III DISASSEMBLY AND REASSEMBLY.................................................III-1
1.SAFETY PRECAUTIONS..................................................................................................III-1
2.DISASSEMBLING FLOW..................................................................................................III-2
3.DISASSEMBLING PROCEDURE.....................................................................................III-3
3.1 Drum Unit.................................................................................................................................III-3
3.2 Top Cover................................................................................................................................III-3
3.3 Multi-purpose Paper Tray Assy..............................................................................................III-4
3.4 Fixing Unit................................................................................................................................III-5
3.5 Scanner Unit............................................................................................................................III-7
3.6 Main PCB Assy .......................................................................................................................III-7
3.7 Base Plate Assy.......................................................................................................................III-8
3.8 Panel sensor PCB Assy...........................................................................................................III-8
3.9 Low-voltage Power Supply PCB Assy.....................................................................................III-9
3.10 High-voltage Power Supply PCB Assy....................................................................................III-9
3.11 Fan Motor...............................................................................................................................III-10
3.12 Drive Unit...............................................................................................................................III-10
3.13 Main Motor Assy and Motor Heat Sink..................................................................................III-11
3.14 Gears and Solenoid...............................................................................................................III-11
3.15 Tray Extension.......................................................................................................................III-12
3.16 Paper Eject Tray Assy...........................................................................................................III-12
4.PACKING........................................................................................................................III-13
CHAPTER IV TROUBLESHOOTING.........................................................................IV-1
1.INTRODUCTION..............................................................................................................IV-1
1.1 Initial Check............................................................................................................................IV-1
1.2 Basic Procedure.....................................................................................................................IV-2
2.IMAGE DEFECTS............................................................................................................IV-3
2.1 Image Defect Examples..........................................................................................................IV-3
2.2 Troubleshooting Image Defects..............................................................................................IV-4
3.TROUBLESHOOTING OF MALFUNCTIONS................................................................IV-12
4.INSPECTION MODE......................................................................................................IV-17
4.1 Incorporated Inspection Modes............................................................................................IV-17
4.2 Error codes...........................................................................................................................IV-19
APPENDICES.............................................................................................................V-1
1. Connection Diagram, HL-720..................................................................................................V-1
2. Connection Diagram, HL-730/730Plus....................................................................................V-2
3a. Main PCB Circuit Diagram (1/2), HL-720.................................................................................V-3
3b. Main PCB Circuit Diagram (2/2), HL-720.................................................................................V-4
4. Main PCB Circuit Diagram (1/2), HL-730/730Plus...................................................................V-5
5. Main PCB Circuit Diagram (2/2), HL-730/730Plus...................................................................V-6
6. Panel/Sensor PCB Circuit Diagram.........................................................................................V-7

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7. Low-Voltage Power Supply PCB Circuit Diagram 230V.......................................................... V-8
8. Low-Voltage Power Supply PCB Circuit Diagram 115V.......................................................... V-9
9. High-Voltage Power Supply PCB Circuit Diagram ................................................................ V-10
10. Serial No. Descriptions .......................................................................................................... V-11

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CHAPTERI 
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Check the following system requirements to setup and operate the printer:
• IBM PC or compatible with 80486 SX or higher microprocessor
• Parallel interface (or printer port)
• 4 Mbytes or more of memory
• 10 Mbytes of space available on your hard disk for the printer driver and all fonts
• Microsoft Windows 3.1/3.11 or Windows 95
Caution: This printer has been designed specially for Windows 3.1/3.11 and Windows 95.
It cannot work in a DOS environment such as MS-DOS.
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This printer has the following features:
600 dpi Resolution and 6 ppm Printing Speed
600 dots per inch (dpi) with microfine toner and six pages per minute
(ppm) printing speed (A4 or Letter size paper).
User-Friendly Operation for Windows
The dedicated printer driver and TrueType™-compatible fonts for
Microsoft® Windows 3.1 and Windows 95 are available on the floppy
disk supplied with your printer. You can easily install them into your
Windows system using our installer program. The driver supports our
unique compression mode to enhance printing speed in Windows
applications and allows you to set various printer settings including
toner saving mode, custom paper size, sleep mode settings, gray
scale adjustment, resolution, and so forth. You can easily set these
print options through the Printer Setup Menu within the Windows
Control Panel.
Printer Status Monitor with Bi-directional Parallel Interface
The printer driver can monitor your printer’s status using bi-directional
parallel communications.
The printer status monitor program can show the current status of
your printer. When printing, the animated dialog box appears on your
computer screen to show the current printing process. If an error
occurs, a dialog box will appear to let you know what to correct. For
example: when your printer is out of paper, the dialog box will display
“Paper Empty” and instructions for the proper corrective action.
Versatile Paper Handling
The printer has a multi-purpose sheet feeder and straight paper path
mechanism. Using this mechanism, you can load A4, letter, legal, B5,
A5, and executive sizes of paper, and various types of paper including
envelopes, postcards, organizer paper, or a custom paper size. The
multi-purpose sheet feeder also allows manual paper loading, so you
can use labels and transparencies.

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Auto Resolution Reduction
When printing in 600 dpi, mode with the standard memory, the printer
may not be able to print due to insufficient memory. To prevent this
memory error, the printer driver automatically reduces the resolution
to 300 dpi or less and for successful printing
Environment-Friendly
Economy Printing Mode
This feature will save your printing cost by saving toner. It is useful to
obtain draft copies for proof-reading. You can select from two
economy modes, 25% toner saving and 50% toner saving, through
the Windows printer driver supplied with your printer.
Sleep Mode
Sleep mode automatically reduces power consumption when the
printer is not in use. The printer consumes less than 7W when in
sleep mode. The time-out for auto sleep mode can be set through the
Windows printer driver.
Low Running Cost
Since the toner cartridge is separate from the Drum Unit, you need to
replace only the toner cartridge after around 2,200 pages printed,
which is cost effective and ecologically friendly.
Enhanced Memory Management
The printer provides its own data compression technology on its
printer hardware and the supplied printer driver software, which can
automatically compress graphic data and font data efficiently into the
printer's memory. You can avoid memory errors and print most full
page 600 dpi graphic and text data, including large fonts, with the
printer's standard memory.
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This printer has the following features:
600 dpi Resolution and 6 ppm Printing Speed
600 dots per inch (dpi) with microfine toner and six pages per minute
(ppm) printing speed (A4 or Letter size paper).
User-Friendly Operation for Windows
The dedicated printer driver and TrueType™-compatible fonts for
Microsoft® Windows 3.1 and Windows 95 are available on the floppy
disk supplied with your printer. You can easily install them into your
Windows system using our installer program. The driver supports our
unique compression mode to enhance printing speed in Windows
applications and allows you to set various printer settings including
toner saving mode, custom paper size, sleep mode settings, gray
scale adjustment, resolution, and so forth. You can easily set these
print options through the Printer Setup Menu within the Windows
Control Panel.
Printer Status Monitor with Bi-directional Parallel Interface
The printer driver can monitor your printer’s status using bi-directional
parallel communications.
The printer status monitor program can show the current status of
your printer. When printing, the animated dialog box appears on your
computer screen to show the current printing process. If an error
occurs, a dialog box will appear to let you know what to correct. For
example: when your printer is out of paper, the dialog box will display
“Paper Empty” and instructions for the proper corrective action.

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Versatile Paper Handling
The printer has a multi-purpose sheet feeder and straight paper path
mechanism. Using this mechanism, you can load A4, letter, legal, B5,
A5, and executive sizes of paper, and various types of paper including
envelopes, postcards, organizer paper, or a custom paper size. The
multi-purpose sheet feeder also allows manual paper loading, so you
can use labels and transparencies.
Environment-Friendly
Economy Printing Mode
This feature will save your printing cost by saving toner. It is useful to
obtain draft copies for proof-reading. You can select from two
economy modes, 25% toner saving and 50% toner saving, through
the Windows printer driver supplied with your printer.
Sleep Mode
Sleep mode automatically reduces power consumption when the
printer is not in use. The printer consumes less than 7W when in
sleep mode. The time-out for auto sleep mode can be set through the
Windows printer driver.
Low Running Cost
Since the toner cartridge is separate from the Drum Unit, you need to
replace only the toner cartridge after around 2,200 pages printed,
which is cost effective and ecologically friendly.
Remote Printer Console Program for DOS
The utility program, Remote Printer Console (RPC), is available on
the floppy disk supplied with your printer. When you operate your
computer in the DOS (Disk Operating System) environment, this
program allows you to easily change the default settings of the printer
such as fonts, page setup, emulations and so on.
This program also provides a status monitor program, which is a
Terminate-and-Stay Resident (TSR) program. It can monitor the
printer status while running in the background and report the current
status or errors on your computer screen.
Popular Printer Emulation Support
This printer supports three printer emulation modes, HP LaserJet IIP,
Epson FX-850, and IBM Proprinter XL. When you use DOS
application software or Windows™ version 3.0 or earlier, you can use
any of these emulations to operate the printer in the 300 dpi resolution
mode. The printer also supports Auto-emulation switching between
HP and Epson or HP and IBM. If you want to set the printer emulation,
you can do it using the Remote Printer Console Program.
Optional Apple Macintosh Interface
The optional Apple Macintosh serial interface kit is available, which
allows your printer to be connected to Apple Macintosh computers.
With this option, you can use your printer with both an IBM PC, or
compatible and an Apple Macintosh at the same time. This optional
interface board can be used as an RS-422A interface for Macintosh or
an RS-232C serial interface for IBM PC or compatible.
Enhanced Memory Management
The printer provides its own data compression technology on its
printer hardware and the supplied printer driver software, which can
automatically compress graphic data and font data efficiently into the
printer's memory. You can avoid memory errors and print most full
page 600 dpi graphic and text data, including large fonts, with the
printer's standard memory.

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3.1 Printing
<HL-720>
Print method Electrophotography by semiconductor laser beam scanning
Resolution 600 dots/inch (under Brother Printing Solution for Windows)
Print speed 6 page/minute (when loading A4 or letter-size paper from the multi-
purpose sheet feeder)
Warm-up Max. 20 seconds at 23°C (73.4°F)
First print 20 seconds (when loading A4 or letter-size paper from the multi-
purpose sheet feeder)
Print media Toner in a cartridge
Life Expectancy: 2,200 pages/cartridge (when printing A4 or letter-
size paper at 5% print coverage)
Developer Drum unit, separated from toner cartridge
<HL-730/730Plus>
Print method Electrophotography by semiconductor laser beam scanning
Resolution 600 dots/inch (under Brother Printing Solution for Windows)
300 dots/inch (under DOS, Apple Macintosh and other operating
system)
Print speed 6 page/minute (when loading A4 or letter-size paper from the multi-
purpose sheet feeder)
Warm-up Max. 20 seconds at 23°C (73.4°F)
First print 20 seconds (when loading A4 or letter-size paper from the multi-
purpose sheet feeder)
Print media Toner in a cartridge
Life Expectancy: 2,200 pages/cartridge (when printing A4 or letter -
size paper at 5% print coverage)
Developer Drum unit, separated from toner cartridge

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3.2 Functions
<HL-720>
CPU Z80 12.5 MHZ
Emulation Windows 3.1 GDI
Printer driver WindowsTM 3.1/3.11 and Windows 95 driver, supporting Brother
Native Compression mode and bi-directional capability
Interface Bi-directional Centronics parallel interface.
Memory 0.5Mbytes
Expandable up to 2.0 Mbytes with an optional memory board.
MB-215W - 1.5 MB
Control panel 1 switch and 4 lamps
Diagnostics Self-diagnostic program
<HL-730/730Plus>
CPU MC68EC000 16 MHz
Emulation Automatic emulation selection among HP LaserJet IIP, EPSON
FX-850, and IBM Proprinter XL
Printer driver WindowsTM 3.1/3.11 and Windows 95 driver, supporting Brother
Native Compression mode and bi-directional capability. Optional
Macintosh® QuickDraw driver (Standard in some countries.)
Interface Bi-directional Centronics parallel interface. RS-422A/RS-232C
serial interface is optionally available.(The serial interface is a
standard in some countries.)
Memory 0.5 Mbytes (HL-730) or 1.0 Mbytes (HL-730Plus) only with Data
Compression Technology.
Expandable up to 2.0 Mbytes with an optional memory board.
MB110 - 1.0 MB (for HL-730/730Plus)
MB115 - 1.5 MB (for HL-730 only)
Control panel 1 switch and 4 lamps
Diagnostics Self-diagnostic program

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3.3 Electrical and Mechanical
<HL-720>
Power source U.S.A. and Canada: AC 110 to 120V, 50/60Hz
Europe and Australia: AC 220 to 240V, 50Hz
Power consumption Printing: 150 W or less
Standing by: 35 W or less
Sleep: 7 W or less
Noise Printing: 48 dB A or less
Standing by: 35 dB A or less
Temperature Operating: 10 to 32.5°C (59 to 90.5°F)
Storage: 0 to 40°C (38 to 104°F)
Humidity Operating: 20 to 80% (without condensation)
Storage: 20 to 80% (without condensation)
Dimensions (W x D x H) 366 (W) x 353 (D) x 250 (H)
(when the output tray is closed and the Multi-purpose sheet feeder
is removed.)
Weight Approx. 6.5 kg (14.3 lb.) including the drum unit
<HL-730/730Plus>
Power source U.S.A. and Canada: AC 110 to 120 V, 50/60Hz
Europe and Australia: AC 220 to 240 V, 50Hz
Power consumption Printing: 150 W or less
Standing by: 35 W or less
Sleep: 7 W or less
Noise Printing: 48 dB A or less
Standing by: 35 dB A or less
Temperature Operating: 10 to 32.5°C (59 to 90.5°F)
Storage: 0 to 40° C (38 to 104°F)
Humidity Operating: 20 to 80% (without condensation)
Storage: 20 to 80% (without condensation)
Dimensions (W x D x H) 366 (W) x 353 (D) x 250 (H)
(when the output tray is closed and the Multi-purpose sheet feeder
is removed.)
Weight Approx. 6.5 kg (14.3 lb.) including the drum unit

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3.4 Paper Specification
(1) Multi-purpose tray loading
Paper size: A4, Letter, Legal, B5, A5, and Executive, and other sizes of paper that can
be handled by the feed mechanism, can be loaded.
Feeding direction
148 to 356 mm (face down)
90 to 229 mm
Feedable paper type: 60(16lb.)to157(42 lb.) g/m2(long-grainedpaper)
Maximum load height: 22 mm (200 sheets of 75 g/m2paper) letter size
Envelopes: 10 envelopes
Setting method: Pull the manual paper tray toward you, insert the
sheet of paper into the tray, aligning the top edge
of the sheets,then push thetray back to its original
position.
(2) Manual paper loading
The manual paper loading takespriorityoffeeding and a single sheet of papercan be fedinto the
printer. The applicable sizes and types of paper are the same as the multi-purpose tray
loading above in specification.
3.5 Print Delivery
(1) At the print delivery tray opened
Tray capacity : Maximum 100 sheets (75g/m2), face-down only
(2) At the print delivery tray closed
Tray capacity : 1 sheet (75 g/m2), face-down only
Note) Face down: Deliver the printed face of the paper downward.
Environment : 23°C
3.6 Paper
(1) Types of paper
(a) Normal paper (60 to 157 g/m2, specified types of high-quality paper)
• A4 size
• Letter size
• Legal size
• B5 size
• A5 size
• Executive size
• 9" envelop size (printing face is Letter size)
*The specified types of plain paper are as follows:
Letter : Xerox 4200 (75 g/m2)
A4 : Xerox 80 Premier Paper

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(b) Special paper (specified types)
• Labels
• Envelopes (DL,C5, COM10)
• Postcards
• Organizers (K, L, and J sizes of DAY-TIMERS)
(2) Paper feed conditions
Types Name Tray feed Manual feed
Normal paper (cut sheet) 60 to 157 g/m2 paper 
Labels 
Special paper (cut sheet) Envelopes 
Postcards 
Organizers 
3.7 Effective Printing Area
Printable area
EA
FCE
BD
F
The effective printing area means the area within which the printing of all the data received
without any omissions can be guaranteed.

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The table below shows the effective printing areas.
Size A B C D E F
A 4 210.0mm 8.27”
(2,480 dots)
297.0mm
11.69”
(3,507 dots)
203.2mm
8.0”
(2,400 dots)
288.5mm
11.36”
(3,407 dots)
3.4mm
0.13”
(40 dots)
4.23mm
0.17”
(50 dots)
Letter 215.9mm 8.5”
(2,550 dots)
279.4mm
11.0”
(3,300 dots)
203.2mm
8.0”
(2,400 dots)
271.0mm
10.67”
(3,200 dots)
6.35mm
0.25”
(75 dots) 
Legal 215.9mm 8.5”
(2,550 dots)
355.6mm
14.0”
(4,200 dots)
203.2mm
8.0”
(2,400 dots)
347.1mm
13.67”
(4,100 dots) 
B 5 (JIS) 182.0mm 7.16”
(2,149 dots)
257.0mm
10.12”
(3,035 dots)
170.0mm
6.69”
(2,007 dots)
248.5mm
9.78”
(2,935 dots)
6.01mm
0.24”
(71 dots) 
B 5 (ISO) 176.0mm 6.93”
(2,078 dots)
250.0mm
9.84”
(2,952 dots)
164.0mm
6.46”
(1,936 dots)
241.5mm
9.5”
(2,852 dots) 
Executive 184.15mm 7.25”
(2,175 dots)
266.7mm
10.5”
(3,150 dots)
175.7mm
6.92”
(2,075 dots)
258.3mm
10.17”
(3,050 dots)
6.35mm
0.25”
(75 dots) 
A 5 148.5mm 5.85”
(1,754 dots)
210.0mm
8.27”
(2,480 dots)
135.8mm
5.35”
(1,604 dots)
201.5mm
7.93”
(2,380 dots)
6.01mm
0.24”
(71 dots) 
Organizer
(J size) 69.85mm 2.75”
(825 dots)
127.0mm
5.0”
(1,500 dots)
56.2mm
2.21”
(663 dots)
118.5mm
4.66”
(1,400 dots)
6.35mm
0.25”
(75 dots) 
Organizer
(K size) 95.25mm 3.75”
(1,125 dots)
171.45mm
6.75”
(2,025 dots)
86.78mm
3.42”
(1,024 dots)
163.0mm
6.42”
(1,925 dots) 
Organizer
(L size) 139.7mm 5.5”
(1,650 dots)
215.9mm
8.5”
(2,550 dots)
131.23mm
5.17”
(1,550 dots)
207.43mm
8.17”
(2,450 dots) 
COM-10 104.78mm 4.125”
(1,237 dots)
241.3mm
9.5”
(2,850 dots)
92.11mm
3.63”
(1,087 dots)
232.8mm
9.16”
(2,750 dots) 
MONARCH 98.43mm 3.875”
(1,162 dots)
190.5mm
7.5”
(2,250 dots)
85.7mm
3.37”
(1,012 dots)
182.0mm
7.16”
(2,150 dots) 
C 5 162mm 6.38”
(1,913 dots)
229mm
9.01”
(2,704 dots)
150.0mm
5.9”
(1,771 dots)
220.5mm
8.68”
(2,604 dots)
6.01mm
0.24”
(71 dots) 
DL 110mm 4.33”
(1,299 dots)
220mm
8.66”
(2,598 dots)
98.0mm
3.86”
(1,157 dots)
211.5mm
8.33”
(2,498 dots) 
(Note that the paper sizes indicated here should conform to the nominal dimensions
specified by JIS.)
A4 paper must accommodate 80 characters printed in pica pitch (203.2 mm).
The dot size is based on 300 dpi resolution.



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
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 

 




4.1 Laser Safety (110 - 120V Model only)
This printer is certified as a Class 1 laser product under the US Department of Health and
Human
Services (DHHS) Radiation Performance Standard according to the Radiation Control for
Health and Safety Act of 1968. This means that the printer dose not produce hazardous
laser radiation.
Since radiation emitted inside the printer is completely confined within the protective
housings and external covers, the laser beam cannot escape from the machine during any
phase of user operation.
4.2 CDRH Regulations (110 -120V Model only)
The Center for Device and Radiological Health (CDRH) of the US Food and Drug
Administration implemented regulations for laser products on August 2, 1976. These
regulations apply to laser products manufactured from August 1, 1976. Compliance is
mandatory for products marketed in the United States. The label shown below indicates
compliance with the CDRH regulations and must be attached to laser products marketed in
the United States.
The label for Japanese products
MANUFACTURED : K
BROTHER INDUSTRIES, LTD.
15-1, Naeshiro-cho, Mizuho-ku, Nagoya 467, Japan.
This product complies with FDA radiation
performance standards, 21 CFR Subchapter J.
The label for Chinese products
MANUFACTURED : C
Brother Corporation (Asia) Ltd.. Shenzhen Buji Nan Ling Factory
Gold Garden Ind., Nan Ling Village, Buji, Rong Gang, Shenzhen,
CHINA.
This product complies with FDA radiation performance standards,
21 CFR Subchapter J.


4.3 Caution for Laser Product
(1) CAUTION: When the machine during serving is operated with open cover, the
regulations of VBG 93 and the performance instructions for VBG 93 are
valid.
(2) CAUTION: In case of any trouble with the laser unit, please replace the laser unit
itself. To prevent direct exposure to the laser beam, do not try to open
the enclosure of laser unit.
(3) Location of the Exit Opening of Laser Beam.
Fig. 1.2
(4) Location of Caution Label for Laser Product.
Fig. 1.3
 

II-1
CHAPTERII THEORY OF OPERATION
1. ELECTRONICS
1.1 General Block Diagram
<HL-720>
Fig. 2.1 shows a general block diagram of this printer.
Optional RAM board
(1.5, 3.5 Mbytes)
Expansion memory I/O
Control system
Video control block Interface block
External device
Low-voltage power
supply block
High-voltage power
supply block
Engine control block Operation block
(Operation panel)
Laser scanner unit
Transfer block
Drum unit
Developing
block Cleaner block
Drum
Charging
block
Toner cartridge
Image generation system
Paper tray unit
Erase lamp
Manual feed
Fixing unit
Paper eject block
Paper tray
Paper feed system
Drive block
(Stepping motor)
Fig. 2.1

II-2
<HL-730/730Plus>
Fig. 2.2 shows a general block diagram of this printer.
Optional RAM board
(1.0, 1.5 Mbytes) Optional I/F board (Mac. RS-232C)
Expansion memory I/O Expansion I/O
Video control block Interface block
Engine control block Operation block
(Operation panel)
Control system
Low-voltage power
supply block
High-voltage power
supply block
Laser scanner unit Drive block
(Stepping motor)
Drum unit Transfer block
Developing
block Drum
Charging
block
Cleaner
block
External deviceExternal device
Paper tray unit
Paper tray
Manual feed
Fixing unit
Paper eject block
Paper feed system
Image generation system
Toner cartridge
Erase lamp
Fig. 2.2

II-3
1.2 Main PCB Block Diagram
<HL-720>
Fig. 2.3 shows a block diagram of the main PCB.
Reset Circuit
DRAM
0.5 Mbytes
Option RAM
1.5 Mbytes or
3.5 Mbytes
EEPROM
(128 x 8 bits)
DRAM Control
Oscillator
(12.27 MHz)
Program ROM
16 Kbytes
Working S-RAM
512 Bytes
Timer
CDCC
Parallel I/O
DATA
Extension
FIFO
EEPROM I/O
Engine
Control I/O
To Panel sensor PCB
To PC
ASIC
CPU Core
(Z80)
BUS INT
Motor Driver
Fig. 2.3