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Brother International IntelliFax-4750 Service Manual - Page 42

Main PCB, analog circuits for scanning, printing, and power transmission shifting.

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3.2 Main PCB 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. EEPROM:Electrically Erasable Programmable Read-only Memory DRAM: Dynamic Random Access Memory *1 Provided on models supporting LAN interface. *2 Provided on models supporting video capture. *3 Provided on models equipped with a handset. Block Diagram of Main PCB III - 13

Section	Page
FAX4750, FAX5750, FAX8350P, FAX8750P, MFC8300, MFC8600, MFC8700, MFC9650 Parts and Service Manual.pdf	1
CHAPTER I. GENERAL DESCRIPTION	6
1. EQUIPMENT OUTLINE	7
1.1 External Appearance and Weight	7
1.2 Components	7
2. SPECIFICATIONS	8
CHAPTER II. INSTALLATION	25
1. INSTALLING THE UPDATE DATA TO THE	26
CHAPTER III. THEORY OF OPERATION	29
1. OVERVIEW	30
2. MECHANISMS	31
2.1 Scanner Mechanism	32
2.1.1 Document feeding and ejecting mechanism	32
2.1.2 Scanner	32
2.2 Laser Printing Mechanism	33
2.2.1 Paper pick-up and registration mechanism	33
2.2.2 Print process mechanism	34
(1) Charging process	35
(2) Exposing process	35
(3) Developing process	36
(4) Transferring process	36
2.2.3 Heat-fixing mechanism	37
2.2.4 Paper ejecting mechanism	38
2.3 Sensors and Actuators	39
3. CONTROL ELECTRONICS	41
3.1 Configuration	41
3.2 Main PCB	42
3.3 Engine PCB	44
3.4 NCU PCB	45
3.5 Control Panel PCB	48
3.6 Power Supply PCB	49
[ 1 ] Low-voltage power supply PCB	49
[ 2 ] High-voltage power supply PCB	50
CHAPTER IV. DISASSEMBLY/REASSEMBLY AND	52
1. DISASSEMBLY/REASSEMBLY	54
Safety Precautions	54
Preparation	55
How to Access the Object Component	55
Disassembly Order Flow	56
1.1 Rear Cover	57
1.2 Access Plates R and F	57
1.3 Control Panel ASSY	58
1.4 Panel Rear Cover and Control Panel	59
1.5 Document Feed Roller ASSY, Document Ejection Roller ASSY, and Pinch Rollers	62
1.6 CIS Unit	63
1.7 Scanner Frame ASSY (Scanner Motor, Scanner Drive Unit, Document Take-in Roller,	64
1.8 Top Cover (Exit Roller, Speaker, and Document Guides)	68
1.9 Handset Mount and Hook Switch PCB (for models equipped with a handset)	74
1.10 Paper Sub Tray	76
1.11 VC Cover, VC Bracket, and VC Connector PCB (for models supporting video capture)	77
1.12 Front Cover	78
1.13 Outer Chute and Paper Pinch Rollers	79
1.14 Main Cover	80
1.15 Switch Cover	81
1.16 Laser Unit	82
1.17 Heat-fixing Unit and FU Lamp	83
1.18 Fan	87
1.19 Drive Gear ASSY and Main Motor ASSY	89
1.20 NCU Shield and NCU PCB	91
1.21 Bottom Plate, Main PCB, and Bottom Insulation Film	93
1.22 Low-voltage Power Supply PCB and Power Inlet	97
1.23 Inner Insulation Film, High-voltage Power Supply PCB, Engine PCB, and 2nd Cassette Relay	99
1.24 Toner Sensor (light-receiver) PCB and Toner Sensor (LED) PCB	101
1.25 Gears and Paper Pick-up Roller	102
1.26 Paper Feed Roller ASSY	103
1.27 Clutch Levers, Cassette Guide L, and Solenoid	104
1.28 Paper Cassette	105
1.29 Cleaning of High-voltage Contacts and Grounding Contacts	106
2. LUBRICATION	108
[ 1 ] Document feed roller ASSY and document ejection roller ASSY	108
[ 2 ] Control panel locks	109
[ 3 ] Scanner frame ASSY, document take-in roller and its shaft, and separation roller and	109
[ 4 ] Top cover	110
[ 5 ] Drive gear ASSY	111
[ 6 ] Paper cassette	112
CHAPTER V. MAINTENANCE MODE	114
1. ENTRY INTO THE MAINTENANCE MODE	115
2. LIST OF MAINTENANCE-MODE FUNCTIONS	116
3. DETAILED DESCRIPTION OF MAINTENANCE-MODE FUNCTIONS	118
3.1 EEPROM Parameter Initialization	118
3.2 Printout of Scanning Compensation Data	119
3.3 ADF Performance Test	121
3.4 Test Pattern 1	122
3.5 Firmware Switch Setting and Printout	123
3.6 Operational Check of LCD	169
3.7 Operational Check of Control Panel PCB	169
3.8 Receiver Volume Adjustment (applicable to the American version only)	171
3.9 Sensor Operational Check	172
3.10 CIS Scanner Area Setting	173
3.11 EEPROM Customizing	173
3.12 Erasure of Received FAX Messages Temporarily Stored in the Flash Memory (not applicable to	174
3.13 Equipment Error Code Indication	174
3.14 Output of Transmission Log to the Telephone Line	175
3.15 Cancellation of the Memory Security Mode (applicable to the European version only)	175
CHAPTER VI. ERROR INDICATION AND TROUBLESHOOTING	177
1. ERROR INDICATION	178
1.1 Equipment Errors	178
[ 1 ] Error messages on the LCD	178
[ 2 ] Error codes shown in the \	181
1.2 Communications Errors	183
2. TROUBLESHOOTING	193
2.1 Introduction	193
2.2 Precautions	193
2.3 Checking prior to Troubleshooting	193
2.4 Troubleshooting Procedures	195
[ 1 ] Control panel related	195
[ 2 ] Telephone related	195
[ 3 ] Communications related	196
[ 4 ] Paper/document feeding related	196
[ 5 ] Print-image related	197
Location of High-voltage Contacts and Grounding Contacts	204
Appendix 1. EEPROM Customizing Codes	206
Appendix 2. Circuit Diagrams	209
A. Main PCB (FAX4750/MFC8300/MFC8600/MFC8700/FAX8350P/MFC9650)	210
A. Main PCB (FAX5750/FAX8750P)	217
B. Modem PCB	224
C. Engine PCB	227
D. NCU PCB	229
E. Control Panel PCB	234
F. Power Supply PCB	236
pl_fax8350_8750_mfc9650.pdf	241
List1(MAIN FRAME)	244
List2(DOCUMENT SCANNER)	246
List3(LASER UNIT)	248
List4(PAPER TRANSPORT)	250
List5(PAPER TRAY)	252
List6(HEAT FIXING UNIT)	254
List7(COVER)	256
List8(CONTROL PANEL)	258
List9(PCB ASSY)	260
List10(ACCESSORIES)	262
List11(PRINTED MATERIAL)	264
List12(CARTON)	266
FAX4750pc.pdf	268
List1(MAIN FRAME)	271
List2(DOCUMENT SCANNER)	273
List3(LASER UNIT)	275
List4(PAPER TRANSPORT)	277
List5(PAPER CASSETTE)	279
List6(HEAT FIXING UNIT)	281
List7(COVER)	283
List8(CONTROL PANEL)	285
List9(PCB ASSY)	287
List10(ACCESSORIES)	289
List11(PRINTED MATERIAL)	291