Name: Brother MFC-J3720
Brand: Brother
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Confidential

MODELS: MFC-J3520/J3720

MFC-J6520DW/J6720DW

MFC-J6920DW/J6925DW

Brother Inkjet MFC

SERVICE MANUAL

June 2013

SM-FAX145

8CAT*

(5)

Read this manual thoroughly before maintenance work.

Keep this manual in a convenient place for quick and easy reference at all times.

Default Chapter4
- Table of Contents4
Regulation12
Safety Information17
Chapter 1 Specifications25
General25
- Media Specification25
- Paper Handling26
- LCD Panel26
- Memory26
- Interface26
- Others27
Fax28
Printer28
Copy28
Scanner29
Software29
Network29
- Wired29
- Wireless29
Suppries/Options30
Service Information30
Paper31
- Printable Area34
Chapter 2 Troubleshooting35
Introduction35
- See "Precautions for Troubleshooting And/Or Disassembly/Assembly" at the End of SAFETY INFORMATION35
- Initial Check35
Overview37
- Cross-Section Drawings37
  - Document Scanning37
  - Printer Part38
- Document Feeding Path/Recording Paper Feeding Path39
  - Document Feeding Path39
  - Recording Paper Feeding Path39
- Parts Names and Functions40
- Block Diagram42
- Components43
Error Indication44
- Error Code44
- Error Messages49
- Communications Error51
Troubleshooting55
- Error Cause and Solutions55
- Recording Paper Size Error (Duplex-Printing/Duplex-Copying)56
- Paper Length Is Longer than 245.9 MM56
- (Detection by Registration Sensor, Switchback Sensor)56
- Paper Length Is Shorter than 143.5 MM56
- Paper Jam During Duplex-Printing57
- Registration Sensor Does Not Detect Paper Feed Within Specified Pulse57
- Cannot Identify a Black Ink Cartridge58
- Cannot Identify a Yellow Ink Cartridge58
- Cannot Identify a Cyan Ink Cartridge58
- Cannot Identify a Magenta Ink Cartridge58
- Head Voltage Fails to be Turned off67
- Head Thermistor Defective68
- Head Driver IC Detects Abnormal Temperature During Operation or Standby68
- Purge Count or Flushing Count Overflown68
- Head Flat Cable Detected to be Not Correctly Inserted69
- Head Voltage Does Not Raise69
- Head Voltage Drops too Quick70
- The Purge Cam Switch Is Not Switching ON/OFF70
- Failed to Detect the Origin of the Purge Cam71
- Abnormal Stop of Purge Cam Being Driven72
- Pump of Maintenance Unit Stopped Abnormally During Exhaustion/Suction72
- Excessive Current Protection Activated for the Driver IC During Purge72
- Excessive Current Protection Activated for the Driver IC During Pump72
- Switchback Sensor Detects no Paper Tray 1 State73
- Head/Carriage Unit Cannot Shift to Head Capping Position73
- Head/Carriage Unit Cannot Shift to Head Uncapping Position73
- Head Property Information Not Input74
- Recording Paper Size Error (During Fax/List Printing)74
- Registration Sensor, Paper Width Sensor Detect Unspecified Papers74
- Recording Paper Size Error (Other than Fax/List Printing)75
- Registration Sensor, Paper Width Sensor Detects Papers Smaller than75
- Recording Paper Jam75
- Paper Width Sensor Cannot Detect Leading Edge of Recording Papers75
- Recording Paper Jam76
- Recording Paper Jam77
- Switchback Sensor Cannot Detect Paper Feeding State Even Papers Are77
- Paper Width Sensor Cannot Detect Origin Specified on the Paper Feed77
- PF Encoder Sensor Cannot Detect Rotation of the Paper Feed Motor78
- Excessive Current Protection Activated for the Driver IC During Paper78
- Paper Feed Motor Cannot Stop. Or, PF Encoder Sensor Cannot Detect79
- Document Scanning Position Sensor Detects Length of Document79
- Document Detection Sensor Detects that Document Is Pulled out During80
- ADF Cover Sensor Detects Opened Cover State80
- A5 Level of First Side CIS Scan Result Is Detected as Abnormal During FAX81
- A6 Level of First Side CIS Scan Result Is Detected as Abnormal During FAX81
- Type of CIS Unit and CIS Type Input Value Does Not Match81
- Matching of Color Parameter Fails81
- Level of Second Side CIS Scan Result Is Detected as Abnormal During82
- CIS Positioning Abnormal (Home Position Cannot be Found.)82
- Level of Second Side CIS Scan Result Detected as Abnormal During FAX82
- Black Level Value Abnormal at Scanning83
- Document Scanning Position Sensor Detects a Document of Which Length84
- Modem Communication Failure84
- Modem Does Not Start Normally Even after Resetting the Modem84
- Wired LAN MAC Address Not Registered85
- Wireless LAN MAC Address Not Registered85
- Recording Paper Feeding Problems88
  - Paper Is Not Fed from Paper Tray88
  - Paper Is Not Fed from Manual Feed Slot89
  - Two or more Sheets of Paper Fed at a Time90
  - Paper Feeding at an Angle90
  - Recording Paper Jam91
  - Prints Only Single Side of the Paper When Duplex-Printing94
- Print-Image Problems95
  - Defective Images95
- Software-Related Problems106
  - Cannot Print Data106
- Network Problems106
  - Cannot Make a Print through Network Connection106
- Control Panel Problems107
  - No Display on LCD107
  - No Display on LED107
  - The Control Panel Does Not Work107
  - Touch Panel Inoperative107
- Document Feeding Problems108
  - Document Can Not be Fed108
  - Document Double Feeding108
  - Document Jam109
  - Wrinkles on Documents111
  - Document Size Not Correctly Detected111
- Scanned-Image Problems112
  - Defective Images112
  - Troubleshooting from Image Defect112
- Fax Problems117
  - No Faxes Can be Sent117
  - No Faxes Can be Received117
  - A Communications Error Occurs118
- Other Problems119
  - The Machine Cannot be Powered on119
  - Memory Card/Pictbridge Does Not Function (no Response)119
  - Data of Memory Card/Pictbridge Does Not Read119
  - Internal Memory Errors120
  - Security Function Lock Related Problems120
  - Ink Cartridge Related Problems120
  - Loud Printing Sound120
Chapter 3 Disassembly and Assembly121
Precautions before Proceeding121
Packing123
Screw Catalogue124
Screw Torque List125
Lubrication126
Overview of Gears131
Routing of Harnesses and Ink Supply Tubes132
Disassembly Flow140
Disassembly Procedure142
- Preparation142
- Head Joint Rubber, Head/Carriage Unit and CR Timing Belt147
- Ink Absorber Box161
- FB Hinge162
- Manual Feed Slot Cover ASSY165
- Document Scanner Side Cover L166
- Document Scanner Side Cover R167
- ADF Unit, Document Scanner Unit and ADF Hinge168
- ADF Document Support172
- ADF Cover ASSY and ADF Cover Side Cover173
- Adf174
- ADF Side Cover L174
- ADF Side Cover R175
- Adf175
- Document Separation Roller ASSY176
- ADF Separation Pad178
- Second Side CIS Unit179
- Second Side CIS Flat Cable181
- First Side Document Scanning Position Sensor PCB and Second Side Document Scanning Position Sensor PCB (Duplex Scanning Models Only)186
- Document Detection Sensor/Document Width Sensor PCB187
- First Side CIS Unit188
- First Side CIS Flat Cable and FFC Film190
- Front Cover L193
- Inner Media Cover194
- Panel ASSY196
- Lcd Pcb Assy198
- Lcd200
- Touch Panel ASSY200
- Nfc Pcb201
- Ink Cartridge Cover201
- Lower Side Cover L202
- Lower Side Cover R202
- Upper Side Cover L203
- Upper Side Cover R203
- Side Cover L and Side Cover R204
- Upper Cover205
- Wireless LAN PCB ASSY206
- Document Scanner Sensor PCB207
- Main PCB ASSY209
- Mj Pcb Assy211
- Jam Clear Cover212
- T1 Bank ASSY214
- Power Supply PCB ASSY215
- Carriage PCB ASSY218
- Ink Refill ASSY220
- Ink Absorber Felt (for Ink Refill ASSY)220
- Ink Cartridge Cover Sensor ASSY221
- CR Encoder Strip222
- Encoder Strip Guard Film223
- Switchback Sensor PCB224
- Carriage Motor ASSY225
- Flushing Base228
- Flushing Box229
- Platen Foam and Switchback Roller230
- PF Encoder Disk and PF Encoder Sensor PCB ASSY232
- Paper Feed Motor234
- Paper Feed Roller236
- Paper Ejection Roller and Platen237
- Maintenance Unit and Ink Absorber Felt (for Maintenance Unit)240
- Inner Chute ASSY241
- Registration Sensor PCB ASSY244
- T1 Paper Pull-In Roller245
- T2 Bank ASSY247
- T2 Paper Pull-In Roller248
- Base Pad249
Chapter 4 Adjustments and Updating of Settings, Required after Parts Replacement250
If You Replace the Main Pcb Assy250
- Customize Destinations (Maintenance Mode 74)252
- Set the CIS Type (Maintenance Mode 59)252
- Install the Firmware (Maintenance Mode 28)252
- Initialize the EEPROM Parameters (Maintenance Mode 01)254
- Restore the Head Calibration Data (Maintenance Mode 68)254
- Set the Serial Number (Maintenance Mode 80)254
- Update the Head Property Data (Maintenance Mode 68)257
- Restore Machine Information (Maintenance Mode 46)257
- Adjust the Touch Panel (Maintenance Mode 78)257
- Acquisition of White/Black Level Data (Maintenance Mode 55)257
- Adjustment of Vertical Print Lines/Software Correction for Inclination257
  - Corrugation/Ruled Lines (Maintenance Mode 65)4257
- Update the Paper Feeding Correction Values (Maintenance Mode 58)257
- Adjust Margins in Borderless Printing (Maintenance Mode 66)257
- Reset Purge and Flushing Counts257
- Write Head Calibration Data (Maintenance Mode 02)258
- Check Scanning and Printing258
If You Replace the Head/Carriage Unit260
- Update the Head Property Data (Maintenance Mode 68)261
- Perform Ink Supply Purge (Maintenance Mode 76)264
- Check Head Nozzles (Maintenance Mode 09)264
- Adjust Head Inclination264
- Adjustment of Vertical Print Lines/Software Correction for Inclination266
  - Corrugation/Ruled Lines (Maintenance Mode 65)266
- Update Paper Feeding Correction Values (Maintenance Mode 58)266
- Adjust Margins in Borderless Printing (Maintenance Mode 66)266
- Write Head Calibration Data (Maintenance Mode 02)266
- Check Scanning and Printing266
- Obtain Machine Information at the User Site (Instruction to the End User)266
If You Replace the Document Scanner Unit, Adf Unit or Cis Unit267
- Set the CIS Type (Maintenance Mode 59) (Not Required after Replacement of the ADF Unit on Simplex Scanning Models)267
- Acquisition of White/Black Level Data (Maintenance Mode 55) (Not Required after Replacement of the ADF Unit on Simplex Scanning Models)267
- Check Scanning267
If You Replace the Panel Assy, Touch Panel, Lcd Unit or Lcd Pcb Assy268
- Adjust the Touch Panel (Maintenance Mode 78) (Not Required after Replacement of the LCD Unit)268
- Check LCD Operation (Maintenance Mode 12) (Not Required after Replacement of the Touch Panel)268
- Check the Operation of the Control Panel Keys (Maintenance Mode 13) (Not Required after Replacement of the Touch Panel or LCD Unit)268
If You Replace the Ink Absorber Box or Flushing Box269
- Reset Purge and Flushing Counts269
IF YOU REPLACE the PAPER FEEDING RELATED PARTS and MAINTENANCE UNIT270
- Check Head Nozzles (Maintenance Mode 09)270
- Adjustment of Vertical Print Lines/Software Correction for Inclination271
  - Corrugation/Ruled Lines (Maintenance Mode 65)271
- Update Paper Feeding Correction Values (Maintenance Mode 58)271
- Adjust Margins in Borderless Printing (Maintenance Mode 66)271
- Check Printing271
Chapter 5 Service Functions272
Maintenance Mode272
- Entry to the Maintenance Mode272
  - How to Enter the Maintenance Mode Exclusive to Service Personnel272
  - How to Enter the End User-Accessible Maintenance Mode274
- List of Maintenance-Mode Functions275
- Detailed Description of Maintenance-Mode Functions276
Other Service Functions344
- Displaying the Firmware Version344
- Moving the Head/Carriage Unit344
- Retrieving the Equipment Log Information345
Chapter 6 Circuit Diagrams and Wiring Diagrams346
Chapter 7 Periodical Maintenance351
Periodical Replacement Parts351
Appendix 1 Serial Numbering System352
Appendix 2 Deletion of User Setting Information354
A2.1 Deleting User Setting Info from the Machine354
Appendix 3 Installing the Maintenance Printer Driver355
Appendix 4 Replacement of Condenser on the Main Pcb363

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Quick Setup Guide44 pages

Product Safety Guide24 pages

Safety Guide20 pages

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Brother MFC-J3720 Specifications

General

Print Technology	Inkjet
Maximum Paper Size	A3
Automatic Document Feeder	Yes
Duplex Printing	Yes
Functions	Print, Copy, Scan, Fax
Scanner Type	Flatbed, ADF
Mobile Printing	Yes
Fax Speed	33.6 kbps
Connectivity	USB, Ethernet, Wi-Fi
Maximum Printing Resolution	1200 x 6000 dpi
Scan Resolution	Up to 2400 x 2400 dpi
Fax Transmission Speed	3 seconds per page
Display	2.7" Touchscreen LCD