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3-89

Confidential

(2) Remove the two taptite bind B M4x12 screws. Release the hook, and open the upper

side of the hold cover 2.

(3) Release the main fan harness from the securing fixtures. Remove the main fan, and pull

out the main fan harness from the hole.

Fig. 3-89

Harness routing: Refer to “11. Rear side of the machine”.

Assembling Note:

• Attach the main fan so that the surface with the label faces out.

Main fan

Label

Taptite bind B M4x12

Hold cover 2

Hook

Main fan harness

Default Chapter1
- Service Manual1
- Open Source Licensing Remarks3
- Other Information3
- Table of Contents4
Safety Information11
- Additional Information17
Chapter 1 Supplemental Specifications19
General19
Network Connectivity27
Service Information28
Supplies30
Media Specifications33
Fax (Only for the Models with Fax Function)33
Copy34
Scanner35
Chapter 2 Error Indications & Troubleshooting36
Introduction36
- Precautions36
- Checks before Commencing Troubleshooting37
Overview39
- Cross-Section Drawing39
  - Printer Part39
  - Scanner Part40
- Paper Feeding41
  - Printer Part41
  - Scanner Part42
- Operation of each Part43
- Block Diagram45
- Main Components46
Error Indications47
- Error Codes48
- Error Messages57
- Communication Errors69
Troubleshooting73
- Error Cause and Remedy73
- Troubleshooting for Paper Feeding Problems117
- Troubleshooting for Image Defects130
  - Image Defect Examples130
  - Troubleshooting According to Image Defect131
- Troubleshooting for Software Problems143
  - Cannot Receive Data143
- Troubleshooting for Network Problems144
  - Cannot Print Via Network Connection144
  - Cannot Connect to Access Point144
- Troubleshooting for Control Panel Problems144
- Troubleshooting for Toner and Drum Problems146
- Troubleshooting for Fuser Unit Problems148
  - Fuser Unit Failure148
- Troubleshooting for Laser Unit Problems148
  - Laser Unit Failure148
- Troubleshooting for PCB Problems149
  - Main PCB Failure149
  - Memory Full149
- Troubleshooting for Document Feeding Problems150
- Troubleshooting for Image Defects153
  - Defect Examples153
  - Troubleshooting According to Image Defect153
- Troubleshooting for Fax Problems157
- Troubleshooting for Other Problems159
Chapter 3 Disassembly/Reassembly161
Safety Precautions161
Packing162
Screw Catalogue163
Screw Torque List164
Lubrication167
Overview of Gears169
Harness Routing171
Disassembly Flow Chart184
- Machine184
Disassembly Procedure187
- Preparation187
- Paper Tray188
- Back Cover / Outer Chute190
- Fuser Cover191
- Fuser Unit192
- MP Cover ASSY195
- Front Cover ASSY197
- Side Cover L198
- Side Cover R199
- Adf/Document Scanner Unit200
- ADF Unit203
  - Hinge L ASSY, Hinge R, Hinge R Support, Hinge Arm R205
  - ADF Cover ASSY, Document Stopper206
  - Gear Cover, ADF Front Cover, Document Sub Tray207
  - Document Separate Roller ASSY209
  - ADF Separation Holder ASSY210
  - Second Side CIS Unit, Second Side CIS Flat Cable (Models with Duplex Printing Only)211
- Panel Unit216
  - Panel PCB ASSY, LCD (for LCD: 4.85 Inch Models)218
  - LCD Relay Flat Cable (for LCD: 3.7 Inch Models)220
  - Panel PCB ASSY, LCD, LCD Relay PCB ASSY LCD Relay Flat Cable (for LCD: 3.7 Inch Models)220
  - Touch Panel ASSY222
  - NFC PCB ASSY (Models with NFC Only)223
- USB Host PCB ASSY224
- First Side CIS Unit, First Side CIS Flat Cable225
- Joint Cover ASSY232
- Modem PCB ASSY (Models with FAX Only)234
- Stack Sensor PCB ASSY (Models with USB Host on the Rear Side Only)236
- Main PCB ASSY / Wireless LAN PCB (Wireless LAN Models Only)237
- External Temperature/Humidity Sensor239
- Laser Unit240
- PF Roller Holder ASSY242
- Low-Voltage Power Supply PCB ASSY243
- Toner Amount Detection Sensor PCB ASSY (Light Emission)246
- Main Fan248
- Filter250
- Relay Front PCB ASSY251
- Registration Clutch / T1 Pickup Clutch252
- Main Frame L ASSY253
- Paper Feed Motor256
- Develop Joint Gear 37 / Develop Joint258
- Toner Amount Detection Sensor PCB ASSY (Light Reception)259
- MP Solenoid260
- Develop Clutch 51R261
- Internal Temperature Sensor262
- Fuser Drive Gear 39263
- Eject Motor265
- Back Cover/Duplex Tray Sensor266
- LT/TT Connector267
- High-Voltage Power Supply PCB ASSY268
- Eject Sensor PCB ASSY271
- MP Roller Holder ASSY / MP Separation Pad ASSY / MP Separation Pad Spring272
- T1 Paper Feed Sensor PCB ASSY / T1 Paper Feed Actuator / T1 Paper Feed Actuator Spring273
- MP Paper Empty Sensor PCB ASSY / MP Paper Empty Actuator 1 / MP Paper Empty Actuator 2275
- Paper Empty Sensor PCB ASSY (Models with USB Host on the Rear Side Only)278
- Registration Front/Rear Sensor PCB ASSY279
Disassembly Procedure (Lt Unit)282
- Paper Tray282
- LT Roller Holder ASSY284
- LT Side Cover L285
- LT Side Cover R286
- LT Front Cover ASSY287
- LT Control PCB ASSY288
- LT Pickup Clutch289
- LT Release Clutch290
- LT Connector ASSY / LT Connector Upper293
- LT Paper Feed Sensor PCB ASSY294
- LT Paper Empty Sensor PCB ASSY297
Chapter 4 Adjusting and Updating Settings as Required after Parts Replacement298
If You Replace the Main Pcb Assy298
- Installing Firmware (Sub Firmware and Main Firmware)299
  - Checking Firmware Version299
  - Installing Firmware300
- Adjusting Touch Panel (Function Code: 61)302
- Initializing the EEPROM of the Main PCB ASSY (Function Code: 01)302
- Configure for Country/Region and Model (Function Code: 74)302
- Activating Memory Writing302
- Setting Serial Number and Entering Adjusted Value of Laser Unit303
- Acquiring White Level Data (Function Code: 55)304
- Adjusting Left-End and Upper-End Print Position (Function Code: 45) (TT Only)304
- Resetting to Factory Shipping State304
If You Replace the Low-Voltage Power Supply Pcb Assy305
- Resetting Irregular Power Supply Counter of the Low-Voltage Power Supply PCB (Function Code: 88)305
If You Replace the Laser Unit306
- Entering Adjusted Value of Laser Unit307
- Resetting Printed Pages Counter of the Laser Unit307
If You Replace the Lcd Panel Assy or Panel Pcb308
- Adjusting Touch Panel (Function Code: 61)308
- Checking LCD Operation (Function Code: 12)308
If You Replace the Adf Unit, First Side Cis Unit, Second Side Cis Unit or Document Scanner Unit309
- Acquiring White Level Data (Function Code: 55)309
- Scanning and Printing Check309
If You Replace the Fuser Unit310
- Resetting Printed Pages Counter of the Fuser Unit310
If You Replace a Pf Kit311
- Resetting Printed Pages Counter of a PF Kit311
If You Replace the Tt / Lt312
- Installing Firmware (Main Firmware)313
  - Checking Firmware Version313
  - Installing Firmware314
- Adjusting Left-End and Upper-End Print Position (TT Only)315
Chapter 5 Service Functions316
Maintenance Mode316
- How to Enter Maintenance Mode316
  - Method of Entering Maintenance Mode for Service Personnel316
  - Method of Entering End-User Accessible Maintenance Mode317
- List of Maintenance Mode Functions318
- Details of Maintenance Mode Functions320
Other Service Functions376
- Print Communication Error List376
- Reset the Drum Unit Counter376
Chapter 6 Wiring Diagram377
- Wiring Diagram377
Chapter 7 Periodical Maintenance380
Safety Precautions380
Periodical Replacement Parts381
- Preparation381
- Fuser Unit382
- Laser Unit386
- PF Kit MP396
- PF Kit 1397
- PF Kit 2/3/4/5399
Appendix 1 Serial Numbering System401
Appendix 2 Deleting User Setting Information402
Appendix 3 Installing the Maintenance Printer Driver403

Brand	Brother
Model	MFC-8540DN
Category	All in One Printer
Language	English

Brother MFC-8540DN Service Manual

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