Brother MFC-7750, FAX-3750 Service Manual
FACSIMILE EQUIPMENT
SERVICE MANUAL
MODEL: FAX3750/FAX-8650P
MFC7750
© Copyright Brother 1998
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.
PREFACE
This publication is a Service Manual covering the specifications, construction, theory of operation,
and maintenance of the Brother facsimile equipment. It includes information required for field
troubleshooting and repair--disassembly, reassembly, and lubrication--so that service personnel
will be able to understand equipment function, to rapidly repair the equipment and order any
necessary spare parts.
To perform appropriate maintenance so that the facsimile equipment is always in best condition
for the customer, the service personnel must adequately understand and apply this manual.
This manual is made up of six chapters and appendices.
CHAPTER I. GENERAL DESCRIPTION
CHAPTER II. INSTALLATION
CHAPTER III. THEORY OF OPERATION
CHAPTER IV. DISASSEMBLY/REASSEMBLY AND LUBRICATION
CHAPTER V. MAINTENANCE MODE
CHAPTER VI. ERROR INDICATION AND TROUBLESHOOTING
Appendix 1. EEPROM Customizing Codes
Appendix 2. Circuit Diagrams
This manual describes the models and their versions to be destined for major countries. The specifications
and functions are subject to change depending upon each destination.
SAFETY INFORMATION
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 does 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.
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: MAY 1998 K
BROTHER INDUSTRIES, LTD.
15-1 Naeshiro-cho, Mizuho-ku, Nagoya 467-8561, Japan.
This product complies with FDA radiation
performance standards, 21 CFR Subchapter J.
CHAPTER I.
GENERAL DESCRIPTION
CONTENTS
1. EQUIPMENT OUTLINE........................................................................................I-1
1.1External Appearance and Weight..................................................................I-1
1.2Components.................................................................................................I-1
2. SPECIFICATIONS................................................................................................I-2
1. EQUIPMENT OUTLINE
1.1 External Appearance and Weight
The figure below shows the equipment appearance and approximate dimensions.
Weight: Machine proper Approx. 7.2 kg
Machine (incl. drum unit & toner cartridge) Approx. 8.5 kg
In package Approx. 12 kg
1.2 Components
The equipment consists of the following major components:
I - 1
*1Provided on the FAX3750/MFC7750.
*2Provided on the FAX-8650P.
2. SPECIFICATIONS
Model FAX3750 MFC7750
Color White (1397) White (1138)
PRINTER Available with option *
Engine/Type [YL (VA)] YL (VA)
PPM [6 ppm] 6 ppm
dpi (output resolution) [600 x 600] 600 x 600
Paper Capacity [200] 200
Emulation (Standard) - PCL4
Standards [Windows GDI (600 x 600)] Windows GDI (600 x 600)
Memory (Typical) [2 MB] 2 MB
Memory (Min.) [1.2 MB] 1.2 MB
Fonts Resident - 24-bit MAP (PCL4Comp)
Fonts Disk Based [Yes - 35TT] Yes - 35TT
Paper Handling [LTR, LGL, A4, B5, A5, OHP] LTR, LGL, A4, B5, A5, OHP
Multi-Purpose Sheet Feeder [Custom Size (2.75 x 5, 8.5 x 14)
Printer Driver [Windows3.1/3.11, 95 and NT4.0 Driver
Utility Software - RPC
Period to go in Sleep Mode [0-99] 0-99
Output Size [LTR, LGL, A4, B5, A5] LTR, LGL, A4, B5, A5
Optional LAN Board No No
Optional Mac Board No No
Interface/Interface Cable [Yes (Bi Centro)/No] Yes (Bi Centro)/Yes
SCANNER Available with option *
Color/Mono [Mono] Mono
dpi [OPT 300 x 600 (1200 x 1200)] OPT 300 x 600 (1200 x 1200)
Gray Scale [256] 256
Twain [Yes] Yes
Formats (Import) [TIFF/BMP/PCX/DCX/BTF/ BTX/MAX/PDF] TIFF/BMP/PCX/DCX/BTF/ BTX/MAX/PDF
Formats (Export) [TIFF/BMP/MAX/PDF] TIFF/BMP/MAX/PDF
ADF (pages) [20] *
OCR [Xerox Textbridge] Yes (Xerox Textbridge)
COPY Yes Yes
dpi 300 x 600 300 x 600
Collating 99 99
Reduction/Enlargement 50, 75, 87, 93, 100, 120, 125, 150, 200% 50, 75, 87, 93, 100, 120, 125, 150, 200%
Sorting Yes Yes
FAX Yes Yes
Modem/Speed (bps) ROCKWELL F288R (33.6K FAX Only) ROCKWELL F288R (33.6K FAX Only)
CCITT Group Super G3 Super G3
Coding Method MH/MR/MMR MH/MR/MMR
Error Correction Mode (ECM) Yes Yes
Transmission Speed (sec) 3 3
Gray Scale 64 64
Super Fine Yes Yes
Smoothing Yes Yes
Multi-Resolution TX Yes Yes
Input/Output Width 8.5" x 8.5" 8.5" x 8.5"
LCD Size 16 x 1 16 x 2
Handset Yes *
Duplex Speaker Phone No No
*1 Optional CD-ROM required.
*2 30 pages under the following conditions: - Temperature: 20°C to 30°C - RH: 50% to 70%
*3 No handset is provided on the Australian and New Zealand versions.
Specifications enclosed in brackets are available if options are used.
Envelop (DL/C5/CM10/Mona)]
with Auto Installer Program]
- Forms type: Xerox 4200 (20 lb/LTR), Xerox 4024 (24 lb/LTR), M.PPC (64 g/m2/A4)
- Loading as shown at right.
(Loading more than 20 pages in any
other way will result in a double feed
or paper jam.)
2
3
I - 2
1
Custom Size (2.75 x 5, 8.5 x 14)
Envelop (DL/C5/CM10/Mona)
Windows3.1/3.11, 95 and NT4.0 Driver with Auto
1
Yes
Installer Program
Yes
2
20 *
Yes
(1/2)
(1/2)
Model FAX-8650P
Color White (1138)
PRINTER Yes
Engine/Type YL (VA)
PPM 6 ppm
dpi (output resolution) 600 x 600
Paper Capacity 200
Emulation (Standard) PCL4
Standards Windows GDI (600 x 600)
Memory (Typical) 2 MB
Memory (Min.) 1.2 MB
Fonts Resident 24-bit MAP (PCL4Comp)
Fonts Disk Based Paper Handling LTR, LGL, A4, B5, A5, OHP
Multi-Purpose Sheet Feeder Custom Size (2.75 x 5, 8.5 x 14)
Printer Driver Windows3.1/3.11, 95 and NT4.0 Driver with Auto
Utility Software -
Period to go in Sleep Mode 0-99
Output Size LTR, LGL, A4, B5, A5
Optional LAN Board No
Optional Mac Board No
Interface/Interface Cable Yes (Bi Centro) / No
SCANNER Color/Mono dpi Gray Scale Twain Formats (Import) Formats (Export) ADF (pages) OCR COPY Yes
dpi 300 x 600
Collating 99
Reduction/Enlargement 50, 75, 87, 93, 100, 120, 125, 150, 200%
Sorting Yes
FAX Yes
Modem/Speed (bps) ROCKWELL F288R (33.6K FAX Only)
CCITT Group Super G3
Coding Method MH/MR/MMR
Error Correction Mode (ECM) Yes
Transmission Speed (sec) 3
Gray Scale 64
Super Fine Yes
Smoothing Yes
Multi-Resolution TX Yes
Input/Output Width 8.5" x 8.5"
LCD Size 16 x 2
Handset No
Duplex Speaker Phone No
*1 Optional CD-ROM required.
*2 30 pages under the following conditions: - Temperature: 20°C to 30°C - RH: 50% to 70%
*3 No handset is provided on the Australian and New Zealand versions.
Specifications enclosed in brackets are available if options are used.
Envelop (DL/C5/CM10/Mona)
Installer Program (Except Germany)
- Forms type: Xerox 4200 (20 lb/LTR), Xerox 4024 (24 lb/LTR), M.PPC (64 g/m2/A4)
- Loading as shown at right.
(Loading more than 20 pages in any
other way will result in a double feed
or paper jam.)
I - 3
Model FAX3750 MFC7750
One-touch Dial 12 x 2 12 x 2
Speed Dial 100 100
Tel-Index Yes Yes
Chain Dialing Yes Yes
Contrast SL/Auto/SD SL/Auto/SD
FAX/TEL Switch Yes Yes
Distinctive Ringing Yes Yes
Caller ID Yes Yes
TAD Interface Yes Yes
Next FAX Reservation Yes, Dual Access Yes, Dual Access
Dual Access Yes Yes
Help Yes Yes
Coverpage Yes, Super Yes, Super
Polling Type Std/Seq Std/Seq
Password Check No No
Delayed Timer Yes, up to 50 Yes, up to 50
Broadcasting Yes, up to 174 Yes, up to 174
Call Reservation Yes Yes
Page Memory (TX) *
Out-of-paper Reception *
4
4
Max 3 MB (300 pages: MMR) Max 3 MB (300 pages: MMR)
Max 3 MB (300 pages: MMR) Max 3 MB (300 pages: MMR)
Callback Message Yes Yes
Super Quickscan Yes Yes
Mail box No No
Multi-Transmission No No
Message Center No No
OGM No No
ICM Recording Time No No
Paging Yes Yes
Toll Saver No No
Fax & Voice Mail Box No No
Fax- & Voice-on-Demand No No
FAX Forwarding Yes Yes
FAX Retrieval Yes Yes
General
Energy Star Compliance Yes Yes
Memory (Standard) 4 MB 4 MB
Memory (Opt Upgrade) No No
Simultaneous Operation Available with option *
[ (PRINTER/FAX, PRINTER/SCAN,
1
Yes (PRINTER/FAX, PRINTER/SCAN,
PRINTER/COPY)
PRINTER/COPY) ]
Data Modem No No
Bundled Software Applications Available with option *
1
Yes
PC-FAX (Send/Receive) [SMSI] SMSI
Scanner Application [Brother] Brother
Viewer Application [Visioneer] Visioneer
Network Application No Class 1 No Yes
*1 Optional CD-ROM required.
*4 According to the Brother chart in standard mode, MMR.
Specifications enclosed in brackets are available if options are used.
(2/2)
I - 4
(2/2)
Model MFC-8650P
One-touch Dial 12 x 2
Speed Dial 100
Tel-Index Yes
Chain Dialing Yes
Contrast SL/Auto/SD
FAX/TEL Switch Yes
Distinctive Ringing No
Caller ID Yes (U.K./French/Belgium/Netherlands versions only)
TAD Interface Yes
Next FAX Reservation Yes, Dual Access
Dual Access Yes
Help Yes
Coverpage Yes, Super
Polling Type Std/Seq/Sec
Password Check No
Delayed Timer Yes, up to 50
Broadcasting Yes, up to 174
Call Reservation Yes
Page Memory (TX) *
Out-of-paper Reception *
Callback Message Yes
Super Quickscan No
Mail box No
Multi-Transmission No
Message Center No
OGM No
ICM Recording Time No
Paging No
Fax & Voice Mail Box No
Fax- & Voice-on-Demand No
FAX Forwarding Yes
FAX Retrieval Yes
General
Memory (Standard) 4 MB
Memory (Opt Upgrade) No
Simultaneous Operation No
Data Modem No
Remote Diagnostics Yes
Memory Security Yes
Memory Backup Yes
Bundled Software Applications
PC-FAX (Send/Receive)
Scanner Application
Viewer Application
Network Application No
Class 1 Yes
*1 Optional CD-ROM required.
*4 According to the Brother chart in standard mode, MMR.
Specifications enclosed in brackets are available if options are used.
4
4
Max 3.0 MB (300 pages: MMR)
Max 3.0 MB (300 pages: MMR)
I - 5
CHAPTER II.
INSTALLATION
CONTENTS
1. INSTALLING THE UPDATE DATA TO THE FACSIMILE EQUIPMENT...............II-1
1. INSTALLING THE UPDATE DATA TO THE
FACSIMILE EQUIPMENT
If the program version is updated or the main PCB is replaced, install the update program onto the
flash ROM of the main PCB.
The program installation requires a host computer satisfying the following requirements:
- CPU Pentium 75 or higher
- RAM 8MB or greater (16MB recommended for Windows 95)
- OS Windows 3.1/3.11 or Windows 95
Connecting the equipment to your computer
(1) Make sure that the equipment's power cord is unplugged from a wall socket.
(2) Make sure that your computer is powered off.
(3) Connect the interface cable to the parallel interface port on the back of the equipment and
secure it with the lock wires.
(4) Connect the other end of the interface cable to the printer port of your computer and secure
it with the two screws.
(5) Power on your computer.
(6) Plug the equipment's power cord into a wall socket.
Host computer
Interface cable
Lock
wires
II - 1
Installing the update data onto the flash ROM of the facsimile equipment
(1) Load the floppy disk which stores the update data and transfer utility into the floppy disk
drive of your computer.
(Or, copy the update data and transfer utility onto the same directory of the hard disk.)
(2) Click the Start button, point to Programs, and then click MS-DOS Prompt to open an MS-
DOS window.
(3) Type the drive letter where the update data and transfer utility are located. If it is a floppy
disk drive, type A:\ from the command line and press the ENTER key.
(4) Check that your computer is connected with the facsimile equipment correctly.
(5) To start the transfer utility transmitting the update data to the flash ROM of the facsimile
equipment, type the following:
A:\ICEN filename /b
Then press the ENTER key.
The equipment beeps and shows the "CONNECTING" on the LCD for one second.
Then, the equipment shows the "DOWNLOADING" on the LCD and starts receiving data
downloaded from the host computer.
During downloading, the equipment beeps intermittently.
Upon completion of the downloading, the equipment beeps continuously.
II - 2
CHAPTER III.
THEORY OF OPERATION
CONTENTS
1. OVERVIEW...........................................................................................................III-1
2. MECHANISMS......................................................................................................III-2
2.1 Scanner Mechanism.....................................................................................III-3
2.1.1 Document feeding and ejecting mechanism..........................................III-3
2.1.2 Scanner................................................................................................III-3
2.2 Laser Printing Mechanism.............................................................................III-4
2.2.1 Paper pulling-in, registration, feeding, and ejecting mechanism.............III-4
2.2.2 Print process mechanism......................................................................III-6
(1)Charging process..........................................................................III-7
(2)Exposing process.........................................................................III-7
(3)Developing process......................................................................III-8
(4)Transferring process.....................................................................III-8
(5)Erasing process............................................................................III-8
2.2.3 Heat-fixing mechanism...........................................................................III-9
2.3 Sensors and Actuators..................................................................................III-10
3. CONTROL ELECTRONICS..................................................................................
3.1 Configuration................................................................................................III-12
3.2 Main PCB.....................................................................................................III-13
3.3 NCU PCB.....................................................................................................III-15
3.4 Control Panel PCB........................................................................................III-16
3.5 Power Supply PCB.......................................................................................III-17
[ 1 ] Low-voltage power supply PCB....................................................III-17
[ 2 ] High-voltage power supply PCB...................................................III-18
III-12
1. OVERVIEW
III - 1
*Not provided on the FAX-8650P.
2. MECHANISMS
The facsimile equipment is classified into the following mechanisms:
n SCANNER MECHANISM - Document feeding and ejecting mechanism
n LASER PRINTING MECHANISM - Paper pulling-in, registration, feeding, and ejecting
n SENSORS AND ACTUATORS
- Document scanning mechanism
mechanisms
- Print process mechanism (consisting of charging,
exposing, developing, transferring, and erasing
processes)
- Heat-fixing mechanism
Document feeding and
ejecting mechanism
SCANNER
Document scanning
mechanism
MECHANISM
Paper pulling-in and
registration mechanism
Print process
mechanism
LASER PRINTING MECHANISM
III - 2
Paper ejecting mechanism
Heat-fixing
mechanism
With paper feeding
mechanism
2.1 Scanner Mechanism
2.1.1 Document feeding and ejecting mechanism
This mechanism consists of the document stacker, automatic document feeder (ADF), document
ejection roller ASSY, and document sensors. (For details about the sensors, refer to Section 2.3.)
If the operator sets documents on the document stacker and starts the scanning operation, the
scanner motor rotates so that the ADF (which consists of the separation roller and ADF parts)
feeds those documents into the equipment, starting from the bottom sheet to the top, page by
page. Each document advances with the document feed roller ASSY to the scanner, and then it is
fed out of the equipment with the document ejection roller ASSY.
2.1.2 Scanner
The scanner uses a contact image sensor (CIS) unit which consists of an LED array illuminating
documents, a self-focus lens array collecting the reflected light, a CIS PCB carrying out
photoelectric conversion to output picture element data, and a cover glass on which a document
advances. When the document passes between the document pressure bar and the cover glass,
it is scanned.
III - 3
2.2 Laser Printing Mechanism
2.2.1 Paper pulling-in, registration, feeding, and ejecting mechanism
III - 4
Paper pulling-in and registration mechanism
The paper pulling-in and registration mechanism consists of the pull-in roller gear (incorporated in
the multi-purpose sheet feeder), planetary gear system, paper feed solenoid, solenoid lever, clutch
release lever, and registration sensor. (For the details about the sensor, refer to Section 2.3.)
If the main motor rotates clockwise, the rotation is transmitted to the intermediate gear of the
planetary gear system. As the intermediate gear rotates, the pull-in roller drive gear also rotates
since the clutch gear is locked by the solenoid lever and the clutch release lever. Accordingly, the
pull-in roller in the multi-purpose sheet feeder rotates to pull in paper into the equipment, a sheet
at a time.
If the paper feed solenoid is retracted and the clutch release lever is operated according to the
cam profile of the pull-in roller gear so as to release the clutch gear, the clutch gear rotates and
the pull-in roller drive gear does not rotate. In this way, the clutch gear switches the transmission
of the motor rotation to the pull-in roller drive gear on and off.
The solenoid on/off timing and the clutch release lever timing allow this mechanism to pull in a
sheet and register it against the registration roller.
Paper feeding and ejecting mechanism
If the main motor rotates clockwise, the rotation is transmitted via the gear train to the drum drive
gear, heater roller drive gear, and paper ejection roller drive gear.
After the paper passes through the heat-fixing process, it will be ejected onto the paper tray.
If the leading edge of the paper pushes up the actuator of the paper ejection sensor, the
photosensor becomes opened, signaling the start of paper ejection. If the trailing edge has passed
through the sensor actuator, the sensor becomes closed, signaling the completion of paper
ejection. Then, the main motor stops rotation.
III - 5
2.2.2 Print process mechanism
The print process unit works with laser beam, electrical charges, and toner. The graph below
shows the transition of electrical charge on the surface of the laser-sensitive drum through the five
processes: charging, exposing, developing, transferring, and erasing processes.
III - 6
(1) Charging process
The high-voltage power supply applies DC bias to the corona wire to generate ion on the grid. The
ion uniformly charges the surface of the laser-sensitive drum to approx. 1000V which is kept by
the varister grounding the grid to the frame.
(2) Exposing process
When the laser-sensitive drum holds a positive electrical charge, the laser beam issued from the
laser unit scans the drum according to the print image to expose the drum surface for neutralizing
the spots where black should be, forming an electrostatic latent image.
III - 7
(3) Developing process
The developing process develops an electrostatic latent image formed on the drum in the
exposing process, into a toner image.
The developer roller attracts the toner particles fed from the toner cartridge by the toner supply
roller, and then conveys them to the contact section with the laser-sensitive drum
On the contact section between the developer roller and drum, the positive toner particles stick to
the neutralized spots on the drum according to the principles of attraction and repulsion,
transforming a latent image into a toner image.
The toner augers (which agitate toner particles in the chamber) and the blade allow toner particles
to be fed onto the developer roller at an even thickness.
(4) Transferring process
When a paper passes between the drum and the transfer roller, the switch "a" (see the above
illustration) is turned on to negatively charge the transfer roller. The toner is positive, so the toner
image formed on the drum will be transferred onto the paper according to the same principle as for
the developing process.
If the toner image fails to stick to the paper due to paper jam or other errors, it will stick to the
transfer roller. To repulse this toner, the switch "b" (see the above illustration) is turned on to
positively charge the transfer roller. The toner returns from the transfer roller to the drum.
Cleaning the drum
In the transferring process, not all the toner particles on the drum are transferred onto the paper
but some toner particles remain on the drum. The cleaner roller cleans the drum surface and
collects the residual toner. When printing starts or during non-printing, the toner collected on the
cleaner roller will be discharged onto the drum and returned to the chamber through the developer
roller for recycling in the subsequent developing process.
(5) Erasing process
The eraser lamp emits light to expose the drum surface, which erases the residual electrical
charge.
III - 8
2.2.3 Heat-fixing mechanism
As the paper passes between the heater roller and the pressure roller in the heat-fixing unit, the
heater roller fuses the toner on the paper.
III - 9
2.3 Sensors and Actuators
This equipment has ten sensors: seven photosensors, two thermisters and a mechanical switch as
described below.
Sensor name Type Located on
Document front sensor Photosensor Control panel PCB ASSY
Document rear sensor Photosensor Control panel PCB ASSY
Top cover sensor Photosensor Main PCB
Sheet feeder cover sensor Photosensor Main PCB
Registration sensor Photosensor Main PCB
Paper ejection sensor Photosensor High-voltage power supply
Toner sensor Photosensor Toner sensor PCB
Toner thermister Thermister Toner sensor PCB
Heater thermister Thermister Heat-fixing unit
Hook switch* Mechanical switch Hook switch PCB*
(Document sensor PCB)
(Document sensor PCB)
PCB
*Not provided on the FAX-8650P.
• Document front sensor which detects the presence of documents.
• Document rear sensor which detects the leading and trailing edges of pages to tell the control
circuitry when the leading edge of a new page has reached the starting position and when the
scan for that page is over.
• Top cover sensor which detects whether the top cover is closed.
• Sheet feeder cover sensor which detects whether the sheet feeder cover is closed.
• Registration sensor which detects the leading and trailing edges of paper, which allows the
controller to determine the registration timing and check paper jam.
• Paper ejection sensor which detects whether the recording paper goes out of the equipment.
• Toner sensor which detects whether there is toner or a toner cartridge is loaded.
• Toner thermister which detects the ambient temperature of the toner cartridge.
• Heater thermister which detects the temperature of the heater roller of the fixing unit.
• Hook switch* which detects whether the handset is placed on the handset mount.
These photosensors are a photointerrupter consisting of a light-emitting diode and a light-sensitive
transistor. Each of them has an actuator separately arranged as shown on the next page.
III - 10
Location of Sensors and Actuators
*Not provided on the FAX-8650P.
III - 11
3. CONTROL ELECTRONICS
(NOTE 1) Provided on the FAX-8650P.
*1 On the document sensor PCB are these sensors:
3.1 Configuration
The hardware configuration of the facsimile equipment is shown below.
- Document rear sensor (PH1)
- Document front sensor (PH2)
*2 On the main PCB are these sensors:
- Top cover sensor (PC1)
- Sheet feeder cover sensor (PC2)
- Registration sensor (PC3)
*3 On the toner sensor PCB are these sensors:
- Toner sensor
- Toner thermister
*4 On the high-voltage power supply PCB is the paper
ejection sensor.
*5 On the hook switch PCB is the hook switch.
(Not provided on the FAX-8650P.)
Configuration of Facsimile Equipment
III - 12
3.2 Main PCB
(Provided on the FAX-8650P)
(Provided on the FAX3750/
The main PCB, which is the nucleus controlling the entire operation of the equipment, consists of a
FAX engine (ASIC), memories, MODEM, motor drive circuitry, sensor detection circuitry, and
analog circuits for scanning, printing, and power transmission shifting.
MFC7750)
EEPROM:Electrically Erasable Programmable Read-only Memory
DRAM: Dynamic Random Access Memory
Block Diagram of Main PCB
III - 13
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