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HP LaserJet 4250 Service Manual - Page 125

Fuser over-temperature protection, Overcurrent/overvoltage protection,

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Figure 5-3 Fuser components Fuser over-temperature protection The fusing heater safety circuit is located on the power supply and constantly monitors the fusing temperature. To protect the fuser from excessive temperatures, the printer has the following three protective functions: ■ The CPU monitors the voltage of the thermistor. If the fuser temperature reaches 240°C (464°F) or higher, the CPU turns off the relay (RL101) to interrupt the power to the fusing heater. ■ If the temperature of the fusing heater continues to rise abnormally and the temperature of the thermistor (TH1) exceeds about 250°C (482°F), the relay 1 (RL101) opens up to cut off the power supply to the fusing heater. ■ When the temperature of the heater exceeds about 250°C (482°F), the thermal switch (TP1) turns off to cut off the power supply to the fusing heater. Overcurrent/overvoltage protection If a short-circuit or other problem on the load side causes an excessive current flow or generates abnormal voltage, the overcurrent/overvoltage protection systems automatically cut off the output voltage to protect the power-supply circuit. If the overcurrent or overvoltage protection system are activated and the power-supply circuit does not generate dc voltage, turn the power off, correct the problem, and then turn the printer on again. The circuit has two fuses (FU1, FU2), which break and cut off the output voltage if overcurrent flows through the alternating current (ac) line. General descriptions 111

Section	Page
Product information	15
Chapter contents	15
Printer configurations	16
Base model	16
n model	17
tn model	18
dtn model	19
dtns model	20
dtnsl models	21
Model and serial numbers	22
Printer overview	23
Hardware components	23
Interface ports	25
Software components	26
Operating systems and printer components	26
Printer drivers	27
Drivers included	27
Additional drivers	28
Select the correct printer driver for your needs	28
Printer driver Help	28
Using the printer drivers	29
Software for Macintosh computers	31
PPDs	31
HP LaserJet Utility	31
Specifications	32
Hardware specifications	32
Electrical specifications	34
Acoustic emissions	36
Print speed specifications	38
Operating environment	38
Media specifications	39
General guidelines	39
Supported media weights and sizes	40
Supported-media specifications tables	40
Paper and print media	44
Printing and storage environment	44
Supported types of media	45
Guidelines for using paper	46
Envelopes	48
Envelope construction	48
Envelopes with double side-seams	49
Envelopes that have adhesive strips or flaps	49
Envelope margins	49
Envelope storage	49
Labels	50
Transparencies	50
Card stock and heavy paper	51
Card stock construction	51
Card stock guidelines	51
Types of media to avoid	52
Hewlett-Packard limited warranty statement	53
Print Cartridge Limited Warranty Statement	55
Service approach	56
Regulatory information	57
FCC regulations	57
Environmental product stewardship program	58
Protecting the environment	58
Ozone production	58
Energy consumption	58
HP LaserJet printing supplies	59
Material safety data sheet	60
For more information	60
Regulatory statements	61
Country-/region-specific safety statements	63
Laser safety statement	63
Canadian DOC statement	63
Japanese VCCI statement	63
Korean EMI statement	63
Finnish laser statement	64
Installation	65
Chapter contents	65
Operating environment	66
Site requirements	67
Software installation	68
Operation	69
Chapter contents	69
Using the control panel	70
Control-panel layout	70
Control-panel lights	71
Control-panel buttons	72
Using the printer Help system	72
Settings and defaults	73
Setting the control-panel display language	73
Control-panel menus	74
Printing control-panel menus	74
To print a control-panel menu map	74
To change a control-panel setting	75
Retrieve Job menu	76
Information menu	77
Paper-handling menu	78
Configure-device menu	82
Printing submenu	82
Print-quality submenu	85
System Setup submenu	88
Stapler/stacker submenu	91
I/O submenu	91
Resets submenu (HP LaserJet 4250/4350 only)	92
Diagnostics menu (HP LaserJet 4250/4350 only)	94
Maintenance	95
Chapter contents	95
Cleaning the printer and accessories	96
Cleaning the fuser	97
Running the cleaning page manually	97
To run the cleaning page manually	97
Running the cleaning page automatically	99
To run the cleaning page automatically	99
Cleaning spilled toner	99
Performing preventive maintenance	100
Resetting the maintenance-kit counter (LJ 4200/4300)	100
Resetting the maintenance-kit counter (LJ 4250/4350)	101
Maintenance kit part numbers	101
Expected life of components	102
Maintaining the stapler unit	103
To remove and replace the stapler unit	103
Loading staples	104
To load staples	104
Downloading a remote firmware update	105
Downloading the new firmware to the printer	105
Remote firmware update through a local Windows port	106
Windows 95, Windows 98, or Windows Me	106
Windows NT 4.0, Windows 2000, Windows XP, or Windows Server 2003	107
Remote firmware update through a Windows network	107
Remote firmware update for UNIX systems	107
Remote firmware update using FTP on a direct network connection	107
Windows operating systems	108
Mac operating systems	109
Remote firmware update using FTP through a browser	110
Remote firmware update using Fetch (Mac OS 8.6 and OS 9.x only)	111
Remote firmware update using the HP LaserJet utility (Mac OS 8.6 and OS 9.x only)	112
Remote firmware update using the LPR command	113
Using HP Web JetAdmin to download the firmware to the printer	114
Printer messages during firmware update	115
Troubleshooting a firmware update	116
Theory of operation	117
Chapter contents	117
Introduction	118
Basic operation of the printer	119
Printer operating sequence	119
Control system overview	119
Pickup-and-feed system overview	120
Laser/scanner system overview	120
Image-formation system overview	120
General descriptions	121
Dc controller PCA	122
Motor and fan control	123
Power supply	124
Fuser-control circuit	124
Fuser over-temperature protection	125
Overcurrent/overvoltage protection	125
Laser/scanner assembly	126
Paper-pickup-and-feed system	128
Pickup-and-feed block	130
Printing from tray 1	131
Printing from tray 2	133
Tray 2, 500-sheet feeder, and 1,500-sheet feeder media-size detection	133
Lifter-driver operation	134
Multiple-feed prevention	135
Media-skew prevention	135
Fuser/delivery block	136
Jam detection	136
Printer pickup delay jam from tray 1	137
Printer pickup delay jam from tray 2	137
Printer pickup stationary jam	137
Printer-delivery wrap jam when feeding regular media	137
Printer delivery wrap-jam when feeding irregular media	137
Printer delivery-delay jams	138
Printer door-open jam	138
Printer residual-media jam	138
Printing from the 500-sheet feeder	139
500-sheet feeder pickup and feeding	140
Printing from the 1,500-sheet feeder	142
1,500-sheet feeder pickup and feeding	143
1,500-sheet feeder lifting mechanism	145
Envelope feeder	146
Envelope-feeder pickup and feeding	146
Envelope feeder jam detection	147
Envelope feeder pickup delay jam	147
Envelope feeder pickup stationary jam	147
Duplexer	148
Reversing and duplexer pickup	149
Duplexer jam detection	150
Stacker and stapler/stacker	151
Stacker	153
Stacker feed and delivery	153
Stacker jam detection	155
Stacker-feed jam	155
Stacker-feed stationary jam	155
Stacker residual-media jam	155
Stapler/stacker	156
Stapler/stacker feed and delivery	156
Staple-mode feed and delivery	158
Stapler unit	162
Stapler-unit operation	163
Staple level-detection	165
Stack-mode feed and delivery	165
Stapler/stacker jam detection	166
Stapler/stacker feed jam	166
Stapler/stacker feed stationary jam	166
Stapler/stacker delivery jam	166
Stapler/stacker residual media jam	166
Image-formation system	167
Electrostatic latent-image formation	169
Primary charging	169
Writing the image	169
Developing the image	170
Transferring the image	171
Fusing the image	172
Cleaning the transfer charging roller and photosensitive drum	173
Print-cartridge memory chip	174
Formatter system	175
PowerSave (LJ 4200/4200L/4300) or Sleep (LJ 4250/4350) Mode	175
Resolution Enhancement technology	176
EconoMode	176
Input/output	176
Parallel interface	176
USB (HP LaserJet 4250/4350 Series printers only)	176
Embedded ethernet print server (HP LaserJet 4250/4350 Series printers only)	176
Expanded I/O	177
Flash (HP LaserJet 4200/4300 Series printers only)	177
CompactFlash card (HP LaserJet 4250/4350 Series printers only)	177
Hard-disk accessory	177
CPU	177
Printer memory	177
Read-only memory	177
Random-access memory	177
DIMM slots	178
Firmware DIMM (LJ 4200/4200L/4300 only)	178
Nonvolatile memory	178
Memory Enhancement technology	178
PJL overview	178
PML	179
Control panel	179
Removing and replacing parts	181
Chapter contents	181
Removal and replacement strategy	182
Required tools	182
Before performing service	183
After completing service	183
Screws used in the printer	184
Parts-removal tree	185
Printer input tray, and cabinet wheel locks	186
Dc controller PCA diagram	187
User-replaceable parts	189
Print cartridge	189
Transfer roller	191
Fuser	192
Tray 1 pickup roller	193
Tray 1 separation pad	195
Tray 2 feed rollers	196
Covers, tray 1, and the rear output bin	200
Accessory covers and the tray 2 extension door	201
Formatter cover	205
Top cover	206
Right-side cover	209
Left-side cover	211
Front cover	212
Tray 1	214
Rear output bin	217
Control-panel display	218
Control-panel overlay	218
Control-panel assembly	219
Main assemblies	223
Firmware DIMM (LJ 4200/4300 only)	224
Formatter assembly	225
Reinstallation notes, formatter	226
Installing a new formatter and a new dc controller (LJ 4250/4350 only)	227
Output-delivery assembly	228
Duplexing-pendulum assembly	231
Laser/scanner assembly	233
Paper-pickup drive assembly	236
Tray 2 lifter-drive assembly	241
Dc controller PCA	244
Reinstallation tip	249
Installing a new formatter and a new dc controller (LJ 4250/4350 only)	249
Power supply	250
Paper-feed belt assembly	257
Motors and fans	259
Main cooling fan (left side)	260
Cooling fan, right side (HP LaserJet 4250/4300/4350 Series printers only)	262
Removing the fan without removing the air duct	262
Removing the fan and the air duct together	265
Print-cartridge motor (HP LaserJet 4250/4300/4350 series printer only)	267
Main motor	269
Pickup and feed assemblies	271
Tray 1 paper-pickup assembly	271
Paper-feed assembly	275
Reinstallation notes for the paper-feed assembly	276
Main drive assembly	277
Registration assembly	280
Sensors and switches	282
Tray 2/500-sheet feeder media-size sensor (PS101)	283
Tray 2 media-size sensor (PS101)	283
500-sheet feeder media-size sensor	284
Tray 1 paper sensor (PS105)	286
Door switch (SW101)	287
Solenoids and clutches	288
Tray 2 pickup solenoid (SL101)	289
Tray 1 pickup solenoid (SL102)	290
Feed-roller clutch (CL101)	291
Accessories	292
500-sheet feeder assembly	292
500-sheet feed rollers	292
500-sheet feeder right-side cover	292
500-sheet feeder control PCA	295
500-sheet feeder lifter-drive assembly	296
500-sheet feeder paper-pickup drive assembly	297
1,500-sheet feeder assembly	302
1,500-sheet feeder feed rollers	302
1,500-sheet feeder separation roller	302
1,500-sheet feeder door	304
1,500-sheet feeder rear cover	305
1,500-sheet feeder right-side cover	306
1,500-sheet feeder control PCA	308
1,500-sheet feeder media-size sensor	310
1,500-sheet feeder lifter-drive assembly	311
1,500-sheet feeder paper-pickup drive assembly	314
Troubleshooting	315
Chapter contents	315
Introduction	316
Troubleshooting process	317
Initial troubleshooting checklist	317
Troubleshooting flowchart	319
Power-on checks	320
Overview	320
Troubleshooting tools	323
Information pages	324
Menu map	325
Configuration page	326
Supplies status page	328
Embedded Web server	329
Gaining access to the embedded Web server	329
Information tab	329
Settings tab	330
Networking tab	330
Other links	331
Printer Status and Alerts software	331
To select status messages	332
To view status messages and information	332
Control-panel menus	333
Using control-panel menus	333
Resets submenu	334
Diagnostics menu	335
Service menu (service PIN codes)	337
Service ID	338
Converting the Service ID to an actual date	338
Restoring the Service ID	338
Printer resets and power-on modes	339
Cold reset	339
To perform a cold reset	339
NVRAM initialization	340
To initialize NVRAM	340
Hard-disk initialization	341
To initialize the hard disk	341
Power-on bypass	342
Skip disk-load	342
Self-test	342
Test pages	343
Engine-test page	343
Formatter test page	344
Interface troubleshooting	345
Communications checks	345
Computer direct connect (parallel) test	345
EIO troubleshooting	345
Jetdirect page/Embedded Jetdirect page (HP LaserJet 4250/4350 Series printers)	346
Display-message troubleshooting	347
Status messages	347
Warning messages	347
Error messages	347
Critical-error messages	347
Alphabetical printer messages	347
Alphabetical printer messages	348
Numerical printer messages	362
Numerical printer messages	362
Paper-path troubleshooting	379
Overview	379
Jam recovery	380
To disable the jam recovery	380
Avoiding jams	381
Persistent jams	382
Basic troubleshooting for persistent jams	382
Data collection	382
General paper-path troubleshooting	382
Paper-path checklist	383
Paper-path test	383
To perform a paper-path test	384
Jams in tray 1	385
Jams in tray 2	386
Jams in tray 3 or tray 4	387
Jams in the paper path	388
Jams in the duplex path	388
Media transport problems	389
Multiple pages feed	389
Media is wrinkled or folded	389
Media is skewed	390
Image-formation troubleshooting	391
Media-related print-quality problems	391
Overhead transparency defects	392
Print-quality problems that are related to the environment	392
Print-quality problems that are related to jams	392
Image defects	393
Image quality	393
Check the print cartridge	394
EconoMode	394
Half self-test functional check	395
Drum-rotation functional check	395
Image defect tables	396
Repetitive-defects troubleshooting	414
Troubleshooting the stacker and the stapler/stacker	416
Initial checks	416
Jam errors	417
Stacker and stapler/stacker paper path	417
Stacker paper-path test	418
Stapler/stacker paper-path test	418
Paper-transport errors	420
Malfunction errors	420
Component errors	421
Printer-component locations	423
Main printer parts	423
Printer switches and sensors	427
Printer motors and fans	428
Printer PCAs	429
Accessory component locations	430
500-sheet feeder main parts	430
500-sheet feeder switches, sensors, solenoids, and PCAs	431
1,500-sheet feeder main parts	432
1,500-sheet feeder switches, sensors, solenoids, and PCAs	434
Stapler/stacker stapler assembly	435
Stacker and stapler/stacker switches and sensors	436
Stacker and stapler/stacker motors and solenoids	437
Stacker and stapler/stacker PCAs	438
Printer and accessory wiring diagrams	439
HP LaserJet 4200 wiring diagram	440
HP LaserJet 4250 wiring diagram	441
HP LaserJet 4300 wiring diagram	442
HP LaserJet 4350 wiring diagram	443
500-sheet feeder wiring diagram	444
1,500-sheet feeder wiring diagram	445
Duplex accessory wiring diagram	446
Envelope-feeder-accessory wiring diagram	447
Stacker-accessory wiring diagram	448
Stapler/stacker-accessory wiring diagram	449
Dc controller connectors diagram	450
General timing diagrams	451
HP LaserJet 4200 general timing diagram	452
HP LaserJet 4250 general timing diagram	453
HP LaserJet 4300 general timing diagram	454
HP LaserJet 4350 general timing diagram	455
Stapler/stacker timing diagram	456
Parts and diagrams	457
Chapter contents	457
Ordering parts and supplies	458
Parts	458
Related documentation and software	458
HP-authorized resellers and support	459
HP service agreements	459
HP Partner Portal	459
Supplies	460
Consumables and accessories	461
Consumables	461
Accessories	462
Memory, fonts, and mass storage	464
Cables and connectivity	466
Formatters, laser/scanners, power supplies, and fusers	467
Assembly locations (1 of 3)	468
Assembly locations (2 of 3)	469
Assembly locations (3 of 3)	470
Covers	472
Internal components	476
Accessories	498
Alphabetical parts list	508
Numerical parts list	517

Match case Limit results 1 per page

Figure 5-3

Fuser components

Fuser over-temperature protection

The fusing heater safety circuit is located on the power supply and constantly monitors the fusing

temperature.

To protect the fuser from excessive temperatures, the printer has the following three protective

functions:

■

The CPU monitors the voltage of the thermistor. If the fuser temperature reaches 240°C (464°F)

or higher, the CPU turns off the relay (RL101) to interrupt the power to the fusing heater.

■

If the temperature of the fusing heater continues to rise abnormally and the temperature of the

thermistor (TH1) exceeds about 250°C (482°F), the relay 1 (RL101) opens up to cut off the

power supply to the fusing heater.

■

When the temperature of the heater exceeds about 250°C (482°F), the thermal switch (TP1)

turns off to cut off the power supply to the fusing heater.

Overcurrent/overvoltage protection

If a short-circuit or other problem on the load side causes an excessive current flow or generates

abnormal voltage, the overcurrent/overvoltage protection systems automatically cut off the output

voltage to protect the power-supply circuit.

If the overcurrent or overvoltage protection system are activated and the power-supply circuit does

not generate dc voltage, turn the power off, correct the problem, and then turn the printer on again.

The circuit has two fuses (FU1, FU2), which break and cut off the output voltage if overcurrent flows

through the alternating current (ac) line.

General descriptions

111