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Overcurrent/overvoltage protection

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Overcurrent/overvoltage protection The low-voltage power supply has a protective function against overcurrent and overvoltage to prevent failures in the power supply circuit. If an overcurrent or overvoltage condition occurs, the system automatically cuts off the output voltage. If the dc power is not being supplied from the low-voltage power supply, the protective function might be running. In such case, turn off the power switch and unplug the power cord. Do not plug in the power cord or turn on the power switch again until the cause is found. WARNING! If you believe the overcurrent or overvoltage protection circuits have been activated, do not plug in the product power cord or turn on the product power until the cause of the failure is found and corrected. In addition, two fuses in the low-voltage power supply protect against overcurrent. If overcurrent flows into the ac line, the fuses melt and cut off the power distribution. 20 Chapter 1 Theory of operation ENWW

Section	Page
Theory of operation	19
Basic operation	20
Major product systems	20
Product block diagram	20
Sequence of operation	21
Normal sequence of operation	21
Formatter-control system	22
Sleep mode	22
Input/output	22
CPU	22
Memory	22
Firmware	23
Memory use	23
PJL overview	23
LEDM overview	23
ACL overview	23
Control panel	24
Engine-control system	25
Motors, fans, clutches, solenoids, switches, and sensors	26
DC controller operations	31
Fuser-control circuit	33
Fuser failure detection	34
Fuser temperature control	35
Fuser protective function	36
Pressure roller cleaning	36
Low-voltage power supply	37
Overcurrent/overvoltage protection	38
High-voltage power supply	39
Laser/scanner system	40
Laser failure detection	41
Image-formation system	42
Electrophotographic process	42
Image formation process	44
Latent-image formation stage	45
Primary charging	45
Laser beam exposure	45
Developing stage	46
Print cartridge	46
Transfer stage	47
Fusing stage	47
Cleaning stage	48
Pickup, feed, and delivery system	49
Photo sensors and switches	50
Main-input tray or priority input slot	52
Jam detection	52
Removal and replacement	53
Introduction	54
Removal and replacement strategy	54
Electrostatic discharge	55
Required tools	55
Before performing service	55
After performing service	56
Post-service test	56
Print-quality test	56
Parts removal order	57
Pickup roller	58
Separation pad	59
Transfer roller	60
Covers	61
Main-input tray	61
Output bin tray extension	62
Left cover, simplex product	63
Remove the left cover, simplex product	63
Left cover, duplex product	65
Remove the left cover, duplex product	65
Right cover, simplex product	68
Remove the right cover, simplex product	68
Right cover, duplex product	70
Remove the right cover, duplex product	70
Duplex door, duplex product	73
Duplex frame, duplex product	74
Remove the duplex frame	74
Cartridge door	75
Control panel	77
Front cover	79
Remove the front cover	79
Rear cover, simplex product	81
Remove the rear cover, simplex product	81
Face-down cover	83
Remove the face-down cover	83
Main assemblies	85
Formatter PCA	85
Laser/scanner assembly	86
Remove the laser/scanner assembly	86
Reinstall the laser/scanner assembly	89
Pickup assembly	90
Remove the pickup assembly	90
Reinstall the pickup assembly	96
Fuser	98
Remove the fuser	98
Reinstall the fuser	104
Main motor	105
Remove the main motor	105
Reinstall the main-motor drive belt	110
Pickup solenoid	111
Remove the pickup solenoid	111
Engine controller PCA	115
Remove the engine controller PCA	115
Reinstall the engine controller PCA	120
Duplex-reverse solenoid, duplex product	122
Remove the duplex-reverse solenoid	122
Main fan, duplex product	125
Remove the main fan	125
Reinstall the main fan	127
Duplex-connector PCA, duplex product	128
Remove the duplex-connector PCA	128
Solve problems	131
Solve problems checklist	132
Troubleshooting process	134
Determine the problem source	134
Power subsystem	135
Power-on checks	135
Tools for troubleshooting	136
Individual component diagnostics	136
Engine diagnostics	136
Engine-test button	136
Components tests	137
Drum rotation functional check	137
Half self-test functional check	137
Diagrams	138
Plug/jack locations	138
Location of connectors	139
Locations of major components	140
General timing charts	143
General circuit diagram	144
Internal print-quality test pages	145
Cleaning page	145
Configuration page	145
Print-quality troubleshooting tools	146
Repetitive defect ruler	146
Interpret control-panel light patterns	146
Clear jams	151
Common causes of jams	151
Jam locations	151
Clear jams from the input trays	152
Clear jams from the duplexer	154
Clear jams from the output areas	156
Clear jams from inside the product	157
Solve repeated jams	159
Change jam recovery	160
Solve paper-handling problems	161
Solve image-quality problems	162
Image defect table	162
Light print or faded	162
Toner specks	162
Dropouts	163
Vertical lines	163
Gray background	163
Toner smear	164
Loose toner	164
Vertical repetitive defects	164
Misformed characters	164
Page skew	165
Curl or wave	165
Wrinkles or creases	165
Toner scatter outline	166
Moisture	166
Change print density	167
Clean the product	168
Clean the pickup roller	168
Clean the paper path	169
Clean the print-cartridge area	171
Clean the exterior	172
Solve performance problems	173
Solve connectivity problems	174
Solve direct-connect problems	174
Solve network problems	174
Service mode functions	176
Product resets	176
Product updates	176
Firmware updates	176
Parts and diagrams	177
Order parts by authorized service providers	178
Order replacement parts	178
Related documentation and software	178
Supplies part numbers	178
Customer self repair parts	179
Service parts	179
Whole-unit replacement part numbers	179
How to use the parts lists and diagrams	180
Assembly locations	181
Base product (no optional trays or accessories)	181
Covers	182
Simplex model	182
Duplex model	184
Internal assemblies	186
Internal assemblies (1 of 3)	186
Internal assemblies (2 of 3)	188
Internal assemblies (3 of 3)	190
PCAs	192
Alphabetical parts list	194
Numerical parts list	197
Service and support	201
Hewlett-Packard limited warranty statement	202
HP's Premium Protection Warranty: LaserJet print cartridge limited warranty statement	203
End User License Agreement	204
Customer self-repair warranty service	206
Customer support	206
Repack the product	207
Service information form	208
Specifications	209
Physical specifications	210
Power consumption	210
Acoustic specifications	210
Environmental specifications	211
Regulatory information	213
FCC regulations	214
Declaration of conformity	215
Certificate of Volatility	216
Safety statements	218
Laser safety	218
Canadian DOC regulations	218
VCCI statement (Japan)	218
Power cord instructions	218
Power cord statement (Japan)	218
EMC statement (Korea)	218
Laser statement for Finland	219
GS statement (Germany)	219
Substances Table (China)	220
Restriction on Hazardous Substances statement (Turkey)	220

Match case Limit results 1 per page

Overcurrent/overvoltage protection

The low-voltage power supply has a protective function against overcurrent and overvoltage to prevent

failures in the power supply circuit. If an overcurrent or overvoltage condition occurs, the system

automatically cuts off the output voltage.

If the dc power is not being supplied from the low-voltage power supply, the protective function might

be running. In such case, turn off the power switch and unplug the power cord. Do not plug in the power

cord or turn on the power switch again until the cause is found.

WARNING!

If you believe the overcurrent or overvoltage protection circuits have been activated, do

not plug in the product power cord or turn on the product power until the cause of the failure is found

and corrected.

In addition, two fuses in the low-voltage power supply protect against overcurrent. If overcurrent flows

into the ac line, the fuses melt and cut off the power distribution.

Chapter 1

Theory of operation

ENWW