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Lexmark C720 Service Manual - Page 78

Lower Feed Unit Theory of Operation

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5024-001 Lower Feed Unit Theory of Operation The lower feed unit is used for two purposes: 1. Provide paper to the printer 2. Provide paper, from the duplex unit, to re-enter the print cycle The lower feed unit has a paper size detection mechanism which has a size lever in Tray 2 and a size sensor (PSL) in the lower feed unit. It also has an empty paper actuator and sensor (PEL). The paper is picked by the paper pick-up clutch (PKCL) transferring motion from the printer to the pick-up roll. The paper is then fed to the printer registration roll. The lower feed unit is also used to transport paper from the duplex unit back to the printers registration roll for two side printing. The lower feed clutch drive (DPKCL) is activated during duplex printing only. 1-48 Service Manual

Section	Page
Notices and Safety Information	13
Laser Notices	13
Safety Information	24
1. General Information	31
Maintenance Approach	31
Tools Required for Service	31
Serial Number	32
Acronyms	33
Standard Features	34
Printer (Main)	34
Printer Options	41
Printer Identification	42
Options Identification	43
Printer Theory of Operation	44
Printer Systems Description	45
Basic Principles of Color Printing	45
Mechanical and Electrical Structures	45
Printer Component Systems	47
Basic Process of Color Printing	48
Print System and Transfer System	49
Structure of OPC Belt (Photo Developer Cartridge)	50
Basic Structure of the Print System	51
Details of the Print System	53
Charging Process	53
Exposing Process	55
Developing Process	56
First Transfer (Drum) Process	58
Belt Discharge (Erase Lamp) Process	60
Belt Cleaning Process	61
Details of the Transfer System	62
Second Transfer (Paper) Process	62
Paper Discharging Process	63
Drum Cleaner Process	64
Details of the Optical System	65
Details of the Paper Transportation System	67
Fusing Unit	69
Fusing Process	71
Control System Structure	72
Electrical System and Function	72
Control of Print Process	73
Print Sequence Diagram	74
Laser Drive Control Circuit	75
Interface Control	77
Lower Feed Unit Theory of Operation	78
Duplex Theory of Operation	79
2. Diagnostic Information	81
Start	81
Service Error Codes	82
Operator Messages	89
Paper Jam Messages	107
Symptom Tables	112
Printer Symptom Table	112
Print Quality Symptom Table	114
Optional Lower Feed Unit Symptom Table	116
Optional Duplex Unit Symptom Table	117
Printer Service Checks	118
901—Yellow Developer Clutch Service Check	118
902—Magenta Developer Clutch Service Check	119
903—Cyan Developer Clutch Service Check	120
904—Black Developer Clutch Service Check	121
905—Yellow/Black Developer Solenoid Service Check	122
906—Magenta/Cyan Developer Solenoid Service Check	123
907—Toner Empty Sensor P.W.B. Board Service Check	124
910—Developer Motor (DM) Drive Service Check	125
911—Main Motor (MM) Service Check	127
915—Control Cooling Fan Service Check	130
916—Ozone Fan Service Check	131
917—Fuser Heater Fan Service Check	132
918—Erase Lamp Service Check	133
920, 922, 923—Fuser Unit Service Check	134
921—Fuser Thermistor Service Check	135
981—Duplex Motor (DPM1, DPM2) Service Check	136
982—Duplex Upper Solenoid (DSOL-U) Service Check	138
983— Duplex Fan (D-FAN) Service Check	139
984—Duplex Lower Solenoid (DSOL-L) Service Check	140
990—Transfer Drum Encoder Sensor (HPSEN) Service Check	141
991—Transfer Roller Cam Clutch (TRCM) Service Check	143
992—Drum Cleaner Brush Cam Clutch (FBCM) Service Check	144
993—Cleaner Clutch (FBCL) Service Check	145
994—Fuser Clutch (FUCL) Service Check	146
995—OPC Belt Cartridge, Belt Marker Sensor (PBS) Service Check	147
997—High Voltage Power Supply Unit (HVU) Service Check	149
OPC Belt (Photo Developer) Cartridge Drive Service Check	150
Operator Panel Service Check	150
Options No Power Service Check	152
Paper Discharge Service Check	153
Printer No Power Service Check	154
Toner Feed Service Check	155
Waste Toner Feed Service Check	156
Paper Feed Service Checks	157
Printer Paper Feed Service Check	157
Lower Feed Unit Paper Feed Service Check	159
Duplex Paper Feed Service Check	161
Print Quality Service Checks	163
Background Service Check	163
Back Stain Service Check	164
Banding Service Check	165
Black Line Service Check	166
Color Misregistration Service Check	167
Insufficient Fusing Service Check	168
Insufficient Gloss Service Check	169
Jitter Service Check	170
Missing Image at Edge Service Check	171
Mixed Color Image Service Check	172
Mottle Service Check	173
Residual Image Service Check	174
Ribbing Service Check	175
Toner Drop Service Check	176
Vertical Line Service Check	177
Vertical Staggering Image Service Check	178
Vertical White Band Service Check	179
White Band Service Check	180
White Line I Service Check	181
White Line II Service Check	182
White Spot / Black Spot Service Check	183
White Print Service Check	184
Wrinkle / Image Migration Service Check	185
Spacing Table	186
Roller Specifications	186
3. Diagnostic Aids	187
Disabling Download Emulations	187
Paper Jam Sequence	188
Diagnostic Mode	191
Diagnostics Menu Structure	192
Print Quality Test Pages	192
Print Registration	193
Setting Tray 2 Left Margin	193
Setting Top Margin	193
Print Tests	194
Hardware Tests	195
LCD Test	195
Button Test	195
Parallel Wrap Test	196
ROM Memory Test	196
DRAM Memory Test	197
Serial Wrap Test	198
Duplex Tests	199
Duplex Left Margin	199
Device Tests	200
Quick Disk Test	200
Disk Test/Clean	200
Flash Test	201
Printer Setup	202
Setting the Page Count	202
Viewing the Permanent Page Count	202
Serial Number	202
Setting Configuration ID	203
Parallel Strobe Adjustment	204
Resetting Counters	205
Error Log	205
Viewing the Error Log	205
Clearing the Error Log	206
Restore EP Factory Defaults	206
Exiting Diagnostic Mode	206
Examples of Print Quality Test Pages	207
4. Repair Information	211
Removal and Cleaning Precautions	211
Handling the Printed Circuit Boards with MOS ICs	212
During Transportation/Storage:	212
During Replacement:	212
During Inspection:	212
Image Belt Cartridge/OPC	213
During Transportation/Storage	213
Handling	213
Parts Not To Be Touched	213
Adjustments	214
Printer Removal Procedures	215
Precautions to Take Before Maintenance Work	215
Printer Covers	216
Upper Side Cover (L) Removal	217
Side Cover (R) Removal	218
Side Cover (L) Removal	220
Side F Cover (L) Removal	221
Top Cover Assembly Removal	222
Paper Exit Cover / Paper Exit Front Cover / Paper Exit Cover (U) Removal	223
Transfer Cover Removal	225
Rear Cover Removal	226
Rear Cover (U) Removal	227
Base Cover (R) Removal	228
Base Cover (L) Removal	230
Cleaner Cover Removal	231
Front Cover Removal	232
Printer Board Removals	233
Printer Board Layout	233
Main Engine (MCTL P.W.B.) Board Removal	234
IOD1 P.W.B. Removal	236
IOD2 P.W.B. Removal	238
Panel P.W.B. (Operator Control) Removal	239
Power Supply Unit (Low Voltage Power Supply - LVPS) Removal	240
High Voltage Power Supply Unit (HVU) Removal	243
Erase Lamp Removal	245
Motor Removals	247
Fan / Motor Layout	247
Main Motor (MM) / BD Gear Assembly Removal	248
Main Gear Unit Removal	250
Developer Motor (DM) Removal	251
Developer Drive Unit Removal	252
Optical Unit (Printhead Scanner Motor Assembly) Removal	254
Control Fan (3) (CTFAN) Removal	257
Heater Fan (HTFAN) Removal	259
Ozone Fan (OZFAN) / Ozone Duct Assembly Removal	260
Clutch and Solenoid Removals	262
Clutch (FUCL, FBCL, RECL) Removal	263
Paper Feeder Clutch (PCLU) Removal	264
Developer Clutch (DCLK, DCLY, DCLM, DCLC) Removal	265
Cam Clutch (FBCM, TRCM) Removal	267
Sensor Removals	268
Interlock Switch (Front) Removal	269
Interlock Switch (Top) Removal	270
Interlock Switch (Rear) Removal	271
Paper Sensor (Paper Feeding Sensor PT1) Removal	273
Paper Exit Sensor (PT2) Removal	274
Paper Empty Sensor (PEU) / OHP Sensor (OHP) Removal	275
Paper Size Sensor (PSU) Removal	277
Drum Jam Sensor (DPJ) Removal	278
Oil Sensor (OIL) Removal	279
Drum Encoder Sensor (HPSEN) Removal	280
Belt Sensor (PBS) Removal	282
Waste Toner Sensor (TBLE/TBFL) (Waste Toner Holder Assembly) Removal	283
Toner Sensor Assembly (TPD) / (TTR) Removal	284
Cleaning Roller Sensor (FCS) Removal	286
Paper Full Sensor (PFUL) Removal	287
Toner Key Sensor (TNK) Removal	288
Transfer Unit (Rollers and Drum) Removal	289
Transfer Unit Removal	289
Registration Roller Removal	290
Transfer Drum Removal	291
Paper Feed Roller / Separator Pad Removal	293
Front Cover Unit Removal	294
Paper Exit Unit / Paper Exit Roller Removal	296
Discharger Brush Removal	298
Waste Toner Feeder (U) (Stay 'A' Assembly) Removal	299
Fuser Connector Removal	300
Waste Toner Feeder (L) Removal	301
Fuser Unit Removal	303
Lower Feeder Unit (LFU) Removals	304
Lower Feeder Unit Top Cover (R) Removal	305
Lower Feeder Unit Top Cover (L) Removal	306
Lower Feeder Unit Front Top Cover Removal	307
Lower Feeder Unit Base Cover (R) Removal	308
Lower Feeder Unit Base Cover (L) Removal	309
Lower Feeder Unit Paper Sensor Removal	310
Lower Feeder Unit Paper Size Sensor (SL-PS -A57 P.W.B. Assembly) Removal	311
Lower Feeder Unit Paper Feed Clutch (PKCLL) / LF Clutch (DPKCL) Removal	312
Lower Feeder Unit Paper Feeder Rolling / Separator Pad Removal	313
Duplex Cover and Paper Guide Removals	314
Duplex Side Cover Low (R) Removal	315
Duplex Side Cover Low (L) Removal	316
Duplex Cover Top (R) Removal	317
Duplex Cover Top (L) Removal	318
Duplex Cover Top (B) Assembly Removal	319
Duplex Cover Top (C) Assembly Removal	321
Duplex Cover Low (B) Assembly Removal	322
Duplex Bottom Cover Assembly Removal	323
Duplex Paper Guide RVS Unit Removal	325
Duplex Paper Guide RVS IN Removal	327
Duplex Paper Guide Bottom Removal	329
Duplex Paper Top Assembly (D-Top Unit and D-Lower Unit) Removal	331
Duplex Paper Guide Top Assembly Removal	333
Duplex Print P.W.B. Removal	334
Duplex Relay P.W.B. Removal	336
Duplex Motor 1 Removal	338
Duplex Motor 2 Removal	339
Duplex Fan Motor Removal	341
Duplex Solenoid (U) Assembly Removal	342
Duplex Solenoid (L) Assembly Removal	343
Duplex Interlock Switch (D-SW1, D-SW2) Removal	344
Duplex Interlock Switch (D-SW3, D-SW4) Removal	345
Duplex D Paper Sensor (PT5) Removal	346
Duplex Paper Sensor Low (PT4) Removal	347
5. Locations	349
Printer	349
Options	351
Electronic Components	352
Sensor Locations	352
Printer Circuit Board Locations	354
Fan/Motor Locations	356
Solenoid/Clutch Locations	357
Symbol and Part Name Table	359
Wiring Diagram / Cable Harness Reference	361
Controller RIP Card	363
Main Engine (MCTL P.W.B.) Board	364
IOD1 P.W.B. Board	365
IOD2 P.W.B. Board	366
Low Voltage Power Supply (LVPS) Board	367
High Voltage Unit (HVU) Board	368
Fuser Unit (LVPS) Board	369
Connector Locations for Options	370
Lower Feed Unit Option	370
Duplex Unit	371
Connector Pin Assignments	372
Location 1	372
Location 2	373
Location 3	373
Location 4	373
Location 5	374
Location 6	375
Location 7	376
Location 8	376
Location 9	377
Location 10	377
Location 11	378
Location 12	379
Location 13	379
Location 14	380
Location 15	380
Location 16	381
Location 17	381
Location 18	381
Location 19	382
Location 20	382
Location 21	383
Location 22	383
Location 23	383
Location 24	384
Location 25	384
Location 26	384
Location 27	385
Location 28	385
Location 29	386
Location 30	386
Location 31	387
Location 32	388
Location 33	388
Location 34	388
Location 35	389
Location 36	389
Location 37	390
Location 38	390
Location 39	391
Location 40	392
Location 41	392
Location 42	393
Printer Cables	394
Cable 1 Connector Assignments	394
Cable 2 Connector Assignments	394
Cable 3 Connector Assignments	395
Cable 4 Connector Assignments	396
Cable 5 Connector Assignments	397
Cable 6 Connector Assignments	397
Cable 7 Connector Assignments	397
Cable 8 Connector Assignments	398
Cable 9 Connector Assignments	398
Cable 10 Connector Assignments	398
Cable 11 Connector Assignments	399
Cable 12 Connector Assignments	399
Cable 13 Connector Assignments	399
6. Preventive Maintenance	401
Safety Inspection Guide	401
Service Precautions	401
Cleaning Procedures	401
Lubrication Specifications	402
Printer Supplies and Maintenance Schedules	403
Cleaning for Maintenance	404
7. Parts Catalog	405
How to Use this Parts Catalog	405
Index	437