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HP LaserJet M1120 Service Manual - Page 60

Step 2: Laser beam exposure, Step 3: Developing, Step 4: Transfer,

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Step 2: Laser beam exposure The laser beam scans the photosensitive drum to neutralize negative charges on parts of the drum. An electrostatic latent image is formed on the drum where negative charges were neutralized. Step 3: Developing The developing cylinder comes in contact with the photosensitive drum to deposit toner onto the electrostatic latent image. NOTE: The charges on the exposed area of the drum are shown as positive in Figure 4-11 Developing on page 44. The charges are actually negative, but they are more positive than the charges on the developing cylinder. Figure 4-11 Developing Toner acquires a negative charge through friction from the developing cylinder and the blade. When the negatively charged toner comes in contact with the drum, the toner adheres to the electrostatic latent image. The image on the drum becomes visible because of the toner. Step 4: Transfer The transfer charging roller, to which a DC positive bias is applied, imparts a positive charge on the print media. When the print media comes in contact with the photosensitive drum, the toner is transferred to the print media. 44 Chapter 4 Operational theory ENWW

Section	Page
Product information	17
Quick access to product information	18
Product comparison	19
Product features	20
Product walkaround	21
Front view	21
Back view	21
Interface ports	22
Serial number and model number location	22
Software description	23
Supported operating systems	23
Supported printer drivers	23
Software included with the product	23
Easy installation for Windows	23
Advanced installation	24
Macintosh software	24
Software for Windows	25
Embedded Web server (network models only)	25
Status Alerts software	25
Other Windows components and utilities	25
Software for Macintosh	26
Embedded Web server (network models only)	26
HP Director	26
Uninstall software	27
Windows	27
Macintosh	27
Media specifications	28
Supported paper and print media sizes	28
Supported paper types and tray capacity	29
Installation	31
Site preparations	32
Operating environment	32
Minimum system requirements	33
What was in the box	34
Install input devices	35
Priority input tray	35
Tray 1	36
Install supplies	37
Install the print cartridge	37
Maintenance	39
Manage supplies	40
Life expectancies of supplies	40
Check and order supplies	40
Store supplies	40
Replace supplies	41
Print cartridge	41
HP policy on non-HP supplies	42
HP fraud hotline	43
Clean the product	44
Clean the exterior	44
Clean the flatbed scanner glass	44
Clean the lid backing	44
Clean the paper path	45
Management tools	46
Information pages	46
Embedded Web server	46
Features	47
Operational theory	49
Basic operation	50
Sequence of operation for the base unit	50
Scanner functions and operation	52
Scanner functions	52
Scanner operation	53
Internal components (base unit)	54
Engine control system	55
Laser/scanner system	57
Pickup/feed/delivery system	58
Image-formation system	59
Removal and replacement	63
Removal and replacement strategy	64
Introduction	64
Removal and replacement warnings, cautions, notes, and tips	64
Electrostatic discharge	65
Required tools	65
Before performing service	65
After performing service	66
Post-service tests	67
Test 1 (print-quality test)	67
Test 2 (copy-quality test)	67
Parts removal order	68
Scanner assembly	69
Link assemblies and scanner support-frame spring	69
Scanner lid	72
Control-panel overlay	73
Control-panel assembly	74
Scanner assembly	76
Product base	81
Print cartridge	81
Separation pad	82
Pickup roller	83
Scanner cushions	86
Media input tray	87
Transfer roller	89
Side covers	90
Print-cartridge door	92
Rear cover and fuser cover	93
Front cover	95
Formatter	97
Power supply	98
Scanner support frame	102
Laser/scanner assembly	105
Main motor	109
Fuser	112
Paper-pickup assembly	116
Drive-gear assembly and drive belt	119
Problem solve	121
Problem-solving checklist	122
Control-panel messages	124
Alert and warning messages	124
Alert and warning message tables	124
Critical error messages	125
Critical error message-tables	125
Clear jams	127
Causes of jams	127
Where to look for jams	128
Clear jams from the input-tray areas	128
Clear jams from the output bin	131
Clear jams from the print-cartridge area	132
Avoid repeated jams	133
Print problems	134
Print-quality problems	134
Improve print quality	134
Print-quality settings	134
Temporarily change print-quality settings	134
Change print-quality settings for all future jobs	134
Identify and correct print defects	135
Print-quality checklist	135
General print-quality issues	136
Scan problems	140
Solve scanned-image problems	140
Scan-quality problems	142
Prevent problems	142
Solve scan-quality problems	142
Copy problems	143
Prevent problems	143
Image problems	143
Media-handling problems	144
Performance problems	146
Functional checks	147
Engine test page	147
Drum rotation test	147
Half self-test functional check	148
Perform a half self-test check	148
Perform other checks	148
Heating element check	149
High-voltage contacts check	149
Check the print-cartridge contacts	149
Check the high-voltage connector assembly	150
Service-mode functions	151
NVRAM initialization	151
Super NVRAM initialization	151
Secondary service menu	151
Problem-solving tools	153
Product information pages and reports	153
Configuration page	153
Demo page	153
Menu map	153
Service menu	154
Restore the factory-set defaults	154
Clean the paper path	154
Archive print	154
Problem-solving diagrams	156
Repetitive image defects	156
Interface ports	157
Formatter connectors	158
ECU connectors	159
Solenoid and motor	160
Rollers	161
Sensors	162
Major components	163
PCAs (base unit)	164
Circuit diagram	165
Firmware updates	166
Parts	167
Ordering information	168
Supplies and hinge tool	168
Cable and interface accessories	168
Whole-unit replacement	169
Control-panel overlays	173
Supplementry documentation and support	176
Parts lists and diagrams	178
Types of screws	179
Scanner assemblies	180
Assemblies	182
External covers and panels	184
Internal components (1 of 3)	186
Internal components (2 of 3)	188
Internal components (3 of 3)	190
Alphabetical parts list	192
Numerical parts list	194
Service and support	197
Hewlett-Packard limited warranty statement	197
Customer self repair warranty service	198
Print cartridge limited warranty statement	199
Customer support	200
HP maintenance agreements	200
Repacking the device	200
Extended warranty	200
Specifications	201
Physical specifications	202
Electrical specifications	202
Power consumption	202
Environmental specifications	203
Acoustic emissions	203
Regulatory information	205
FCC compliance	206
Environmental product stewardship program	206
Protecting the environment	206
Ozone production	206
Power consumption	206
Toner consumption	206
Paper use	206
Plastics	207
HP LaserJet print supplies	207
Return and recycling instructions	207
United States and Puerto Rico	207
Multiple returns (two to eight cartridges)	207
Single returns	207
Shipping	207
Non-US returns	208
Paper	208
Material restrictions	208
Disposal of waste equipment by users in private households in the European Union	208
Material Safety Data Sheet (MSDS)	208
For more information	208
Declaration of conformity	210
Safety statements	211
Laser safety	211
Canadian DOC regulations	211
EMI statement (Korea)	211
Laser statement for Finland	212
Substances table (China)	212

Match case Limit results 1 per page

Step 2: Laser beam exposure

The laser beam scans the photosensitive drum to neutralize negative charges on parts of the drum. An

electrostatic latent image is formed on the drum where negative charges were neutralized.

Step 3: Developing

The developing cylinder comes in contact with the photosensitive drum to deposit toner onto the

electrostatic latent image.

NOTE:

The charges on the exposed area of the drum are shown as positive in

Figure

Developing

on page

. The charges are actually negative, but they are more positive than the charges on the

developing cylinder.

Figure 4-11

Developing

Toner acquires a negative charge through friction from the developing cylinder and the blade. When the

negatively charged toner comes in contact with the drum, the toner adheres to the electrostatic latent

image. The image on the drum becomes visible because of the toner.

Step 4: Transfer

The transfer charging roller, to which a DC positive bias is applied, imparts a positive charge on the print

media. When the print media comes in contact with the photosensitive drum, the toner is transferred to

the print media.

Chapter 4

Operational theory

ENWW