Brother FAX 750 User manual

FACSIMILE EQUIPMENT
SERVICE MANUAL
MODEL: FAX750/FAX770/FAX870MC
FAX-910/FAX-920/FAX-921/FAX-930/FAX-931
MFC-925/MFC970MC

©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.

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

I- 1
1. EQUIPMENT OUTLINE
1.1 External Appearance and Weight
The figure below shows the equipment appearance and approximate dimensions.
Weight: Machine proper (excluding a ribbon cartridge) Approx. 4 kg (8.82 lbs.)
In package Approx. 6 kg (13.23 lbs.)
1.2 Components
The equipment consists of the following major components:

I- 2
2. SPECIFICATIONS
Model Name FAX750 FAX770
Engine Thermal transfer Thermal transfer
Color Black (1395) White (1397)
Transmission Speed (sec) 15 15
Modem Speed (bps) 9600 9600
Group Compatibility G3 G3
Input/Output Width 8.5"/8.5" 8.5"/8.5"
ADF (pages) 10 10
Recording Paper Loadable 100 sheets 100 sheets
Ribbon Life (Letter-size print) 250 pages (77 m) 250 pages (77 m)
Starter Ribbon Life (Letter-size print) 100 pages (30 m) 100 pages (30 m)
LCD Size 16 x 1 16 x 1
On-Screen Programming Yes Yes
Super Fine Yes Yes
Smoothing Yes Yes
Gray Scale (levels) 64 by Dithered 64 by Dithered
One Touch 8 8
Speed Dial 40 40
Telephone Index Yes Yes
Speaker Phone Monitor Monitor
Handset Yes Yes
FAX/TEL Switch Yes Yes
Distinctive Ring Detection* Yes Yes
Caller ID* Yes Yes
Call Waiting Caller ID* Yes Yes
TAD Interface Yes Yes
Enhanced Remote Activation Yes Yes
Automatic Redial Yes Yes
Next-FAX Reservation Yes Yes
Multi-Resolution Transmission Yes Yes
Polling Type Std/Seq Std/Seq
Delayed Transmission 1-timer 1-timer
Call Reservation Yes Yes
Electronic Coverpage Yes - Super Yes - Super
Call Back Message Yes Yes
Activity Report Yes Yes
TX Verification Report Yes Yes
Memory Capacity (pages) 512 KB (20 pages) 512 KB (20 pages)
ECM Yes Yes
Broadcasting Yes Yes
Quick-Scan Yes Yes
Out-of-Paper Reception Yes Yes
Multi-Copying w/ Sorting Yes Yes
Enlargement/Reduction Ratio Yes (50-150%) Yes (50-150%)
Multi-Transmission No No
Confidential Mailbox No No
Auto Reduction Yes Yes
Message Center No No
TAD Recording Time No No
Fax Forwarding/Paging No Yes
Fax Retrieval No Yes
Fax-/Voice-on-demand No No
Fax & Voice Mailbox No No
Help List Yes Yes
Missing Link/Multifunction Link Ready Ready
Optional Memory No No
Voice Alarm No No
Others
* Check your local telephone company for availability of this service.

I- 3
Model Name FAX870MC MFC970MC
Engine Thermal transfer Thermal transfer
Color White (1397) White (1138)
Transmission Speed (sec) 9 9
Modem Speed (bps) 14,400 14,400
Group Compatibility G3 G3
Input/Output Width 8.5"/8.5" 8.5"/8.5"
ADF (pages) 10 10
Recording Paper Loadable 100 sheets 100 sheets
Ribbon Life (Letter-size print) 250 pages (77 m) 250 pages (77 m)
Starter Ribbon Life (Letter-size print) 100 pages (30 m) 100 pages (30 m)
LCD Size 16 x 1 16 x 1
On-Screen Programming Yes Yes
Super Fine Yes Yes
Smoothing Yes Yes
Gray Scale (levels) 64 by Dithered 64 by Dithered
One Touch 8 8
Speed Dial 40 40
Telephone Index Yes Yes
Speaker Phone Full duplex (digital) Full duplex (digital)
Handset Yes Yes
FAX/TEL Switch Yes Yes
Distinctive Ring Detection* Yes Yes
Caller ID* Yes Yes
Call Waiting Caller ID* Yes Yes
TAD Interface Yes Yes
Enhanced Remote Activation Yes Yes
Automatic Redial Yes Yes
Next-FAX Reservation Yes Yes
Multi-Resolution Transmission Yes Yes
Polling Type Std/Seq Std/Seq
Delayed Transmission 1-timer 1-timer
Call Reservation Yes Yes
Electronic Coverpage Yes - Super Yes - Super
Call Back Message Yes Yes
Activity Report Yes Yes
TX Verification Report Yes Yes
Memory Capacity (pages) 512 KB (20 pages) 512 KB (20 pages)
ECM Yes Yes
Broadcasting Yes Yes
Quick-Scan Yes Yes
Out-of-Paper Reception Yes Yes
Multi-Copying w/ Sorting Yes Yes
Enlargement/Reduction Ratio Yes (50-150%) Yes (50-150%)
Multi-Transmission No No
Confidential Mailbox No No
Auto Reduction Yes Yes
Message Center Yes Yes
TAD Recording Time 15 minutes 15 minutes
Fax Forwarding/Paging Yes Yes
Fax Retrieval Yes Yes
Fax-/Voice-on-demand Voice-on-demand Voice-on-demand
Fax & Voice Mailbox Yes Yes
Help List Yes Yes
Missing Link/Multifunction Link Ready Included
Optional Memory No No
Voice Alarm No No
Others
* Check your local telephone company for availability of this service.

I- 4
Model Name FAX-910 FAX-920/921
Engine Thermal Transfer Thermal Transfer
Color Black(1395) Black(1395)/White(1397/1138)
Transmission Speed (sec) 15 15
Modem Speed (bps) 9600 9600
Group Compatibility G3 G3
Input/Output Width 8.5"/8.5" 8.5"/8.5"
ADF (pages) 10 10
Recording Paper Loadable 100 sheets 100 sheets
Ribbon Life (A4-size print) 235 pages 235 pages
Starter Ribbon Life (A4-size print) 90 pages (30 m) 90 pages (30 m)
LCD Size 16 X 1 16 X 1
On-Screen Programming Yes Yes
Super Fine Yes Yes
Smoothing Yes Yes
Gray Scale (levels) 64 by Dithered 64 by Dithered
One Touch 16 w/SHIFT KEY 16 w/SHIFT KEY
Speed Dial 32 32
Telephone Index Yes Yes
Speaker Phone Monitor Monitor
Handset No Yes
FAX/TEL Switch Yes Yes
Caller ID Yes HOL/SWE/UK/FRA/NOR Yes HOL/SWE/UK/FRA/NOR
Call Waiting Caller ID No No
Distinctive Ringing No No
TAD Interface Yes Yes
Enhanced Remote Activation Yes Yes
Automatic Redial Yes Yes
Next-FAX Reservation Yes Yes
Multi-Resolution Transmission Yes Yes
Polling Type Sim/Sec/Del/Seq Sim/Sec/Del/Seq
Delayed Transmission 3-timer 3-timer
Call Reservation Yes Yes
Electronic Coverpage Yes - Super Yes - Super
Call Back Message Yes Yes
Journal Report Yes Yes
TX Verification Report Yes Yes
Memory Capacity (pages) 512KB (20 pages) 512KB (20 pages)
ECM Yes Yes
Broadcasting Yes Yes
Quick-Scan Yes Yes
Out-of-Paper Reception Yes Yes
Multi-Copying w/Sorting Yes Yes
Enlargement/Reduction Ratio Yes (50-150%) Yes (50-150%)
Multi-Transmission Yes Yes
Confidential Mailbox No No
Auto Reduction Yes Yes
Message Manager No No
TAD Recording Time No No
Fax Forwarding/Paging Yes - Only Fax forwarding Yes - Only Fax forwarding
Fax Retrieval Yes Yes
Fax-/Voice-on-demand No No
Fax & Voice Mailbox No No
Help List Yes Yes
MFL PRO for Fax Ready Ready
Optional Memory No No
Memo Manager No No
Mute Key No Yes-music on hold; Green Sleeves
Backup for Clock 9 hours 9 hours
Output Tray Option (CT70) Option (CT70)
Backup for Page Memory No No

I- 5
Model Name FAX-930/931 MFC-925
Engine Thermal Transfer Thermal Transfer
Color Black(1395)/White(1397/1138) White(1138)
Transmission Speed (sec) 915
Modem Speed (bps) 14,400 9600
Group Compatibility G3 G3
Input/Output Width 8.5"/8.5" 8.5"/8.5"
ADF (pages) 10 10
Recording Paper Loadable 100 sheets 100 sheets
Ribbon Life (A4-size print) 235 pages 235 pages
Starter Ribbon Life (A4-size print) 90 pages (30 m) 90 pages (30 m)
LCD Size 16X1 16X1
On-Screen Programming Yes Yes
Super Fine Yes Yes
Smoothing Yes Yes
Gray Scale (levels) 64 by Dithered 64 by Dithered
One Touch 16 w/SHIFT KEY 16 w/SHIFT KEY
Speed Dial 32 32
Telephone Index Yes Yes
Speaker Phone Full duplex (digital) Monitor
Handset Yes Yes
FAX/TEL Switch Yes Yes
Caller ID Yes HOL/SWE/UK/FRA/NOR Yes HOL/SWE/UK/FRA/NOR
Call Waiting Caller ID No No
Distinctive Ringing No No
TAD Interface Yes Yes
Enhanced Remote Activation Yes Yes
Automatic Redial Yes Yes
Next-FAX Reservation Yes Yes
Multi-Resolution Transmission Yes Yes
Polling Type Sim/Sec/Del/Seq Sim/Sec/Del/Seq
Delayed Transmission 3-timer 3-timer
Call Reservation Yes Yes
Electronic Coverpage Yes - Super Yes - Super
Call Back Message Yes Yes
Journal Report Yes Yes
TX Verification Report Yes Yes
Memory Capacity (pages) 512KB (20 pages) 512KB (20 pages)
ECM Yes Yes
Broadcasting Yes Yes
Quick-Scan Yes Yes
Out-of-Paper Reception Yes Yes
Multi-Copying w/Sorting Yes Yes
Enlargement/Reduction Ratio Yes (50-150%) Yes (50-150%)
Multi-Transmission Yes Yes
Confidential Mailbox No No
Auto Reduction Yes Yes
Message Manager Yes No
TAD Recording Time 15 minutes No
Fax Forwarding/Paging Yes - both Yes - Only Fax forwarding
Fax Retrieval Yes Yes
Fax-/Voice-on-demand Voice-on-demand No
Fax & Voice Mailbox Yes No
Help List Yes Yes
MFL PRO for Fax Ready Included
Optional Memory No No
Memo Manager No No
Mute Key Yes-music on hold; Green SleevesYes-music on hold; Green Sleeves
Backup for Clock 15 hours 9 hours
Output Tray Option (CT70) Option (CT70)
Backup for Page Memory 6 hours No

CHAPTER II.
INSTALLATION

CHAPTER III.
THEORY OF OPERATION

CONTENTS
1. OVERVIEW...............................................................................................................III-1
2. MECHANISMS..........................................................................................................III-2
2.1 Transmitting Mechanism (Feeding and scanning documents).........................III-2
2.1.1 Automatic document feeder (ADF)...........................................................III-2
2.1.2 Scanner.....................................................................................................III-3
2.2 Receiving Mechanism (Feeding paper and printing data).................................III-4
2.3 Power Transmission Mechanism......................................................................III-5
2.3.1 Structure of the gear train.........................................................................III-5
2.3.2 Description of planetary gear system........................................................III-6
2.3.3 Power transmission for four operation modes..........................................III-7
2.3.4 Power transmission route..........................................................................III-14
2.4 Sensors and Actuators......................................................................................III-16
3. CONTROL ELECTRONICS......................................................................................III-19
3.1 Configuration.....................................................................................................III-19
3.2 Main PCB..........................................................................................................III-20
3.3 NCU PCB..........................................................................................................III-22
3.4 Control Panel PCB............................................................................................III-24
3.5 Power Supply PCB............................................................................................III-25

III - 1
1. OVERVIEW
*Not provided on the FAX-910.

III - 2
2. MECHANISMS
The facsimile equipment is classified into the following mechanisms:
nTransmitting Mechanism Feeding and scanning documents
nReceiving Mechanism Feeding paper and printing data
nPower Transmission Mechanism Switching the power transmission route
nSensors and Actuators
2.1 Transmitting Mechanism (Feeding and scanning documents)
The transmitting mechanism consists of the document stacker, automatic document feeder (ADF),
document feeding related rollers, scanner, and document sensors. (For details about the sensors,
refer to Section 2.4.)
For the drive power source, refer to Section 2.3.
2.1.1 Automatic document feeder (ADF)
If the operator sets documents on the stacker and starts the transmitting operation, the ADF
(consisting 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 to the scanner
with the LF roller, and then it is fed with the document ejection roller.

III - 3
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 - 4
2.2 Receiving Mechanism (Feeding paper and printing data)
The receiving mechanism consists of the recording paper cover ASSY, paper feed roller ASSY,
platen, thermal recording head, paper ejection roller, and sensors. (For details about the sensors,
refer to Section 2.4.)
STEP 1: In the paper feeding mode
If the equipment receives data, the control electronics activates the solenoid and rotates the motor
counterclockwise to drive the paper feed roller (and paper ejection roller). This pulls in a sheet of
paper and feeds it until its leading edge reaches the point just before the printing position.
STEP 2: In the recording (platen drive & ribbon take-up) mode
The control electronics deactivates the solenoid and rotates the motor clockwise to drive the platen
gear and the ribbon take-up gear as well as the paper ejection roller. This feeds the paper up to the
printing position where the thermal recording head prints, as well as feeding the thermal ink ribbon.
STEP 3: In the paper ejection mode
The same operation as for STEP 1 takes place so as to eject the paper.

III - 5
2.3 Power Transmission Mechanism
The equipment has a single drive motor whose power transmission route can be switched by the
planetary gear systems and the solenoid. This switching allows the equipment to function in four
operation modes (scanning, paper feeding/ejecting, recording, and copying modes). For the details
about the planetary gear systems, refer to Subsection 2.3.2.
2.3.1 Structure of the gear train
All of the motor and gears are located at the left side of the equipment. As illustrated in the figure
below (On the outer side of the drive unit), the rotational torque of the motor on the drive unit is
transmitted via the gears on the drive unit to the gears on the main frame, to those on the control
panel ASSY, and to those on the platen frame.
If gear 39/62 of the friction torque transmission ASSY ("V" in the figure below) rotates, gear 20 ("z")
on the inner side of the drive unit also rotates. The rotational torque is further transmitted to the
ribbon drive gear ("w") which drives the ribbon take-up gear ("a") on the ribbon cartridge, as shown
in the figure below (On the inner side of the drive unit).
On the outer side of the drive unit and on the left sides of the platen frame,
main frame and control panel ASSY
On the inner side of the drive unit
Gear Train

III - 6
2.3.2 Description of planetary gear system
The equipment uses the following three planetary gear systems:
- Sun gear 24/90 ("B" in the figure given on the previous page) and its planet gears
- Sun gear 65/60 ("K") and its planet gear
- Sun gear 24/28 ("O") and its planet gear
This section describes the planetary gear system of sun gear 24/90 ("B"). It consists of sun gear
24/90, two planet gears 34, arm A, and arm B as shown below.
Planetary Gear System
If the motor rotates, sun gear 24/90 rotates so that the rotational torque is transmitted to the
engagement between the sun gear and planet gears 34. Since the arms and planet gears are so
designed that the moment of the arms is less than that of the planet gears, the arms turn around
the center shaft in the same direction as sun gear 24/90.
If the planet gear(s) becomes engaged with any other gear so that the arm cannot turn furthermore,
the rotational torque of sun gear 24/90 is transmitted to that planet gear. Accordingly, the planet
gear starts rotation in the opposite direction of sun gear 24/90.

III - 7
2.3.3 Power transmission for four operation modes
Depending upon the solenoid ON/OFF state and the motor rotation direction, the planetary gear
train switches the power transmission route for the four operation modes.
Solenoid ON/OFF state Motor rotation direction