l-l I-2 I-3 I-4 I-5 I-6 2-1 2-2 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 4-1 4-2 4-3 4-4 4-5 4-6 4-7 5-1 5-2 5-3 !i-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13 5-14 5-15 5-16 5-17 5-18 5-19
Sample Model and Serial Number Labels 1-3 External Assembly Locations (LaserJet 4L/4ML) -1-6 External Assembly Locations (LaserJet 4P/4MP) -1-7 Internal Assembly Locations (all printers) 1-8 LaserJet 4L Internal Assembly Locations 1-9 LaserJet 4P Internal Assembly Locations 1-10 Printer Space Requirements 2-3 Distributing Toner 2-6 Attaching the Help Labels (LaserJet 4L/4ML) 3-6 LaserJet 4L/4ML Front Control Panel 3-9 LaserJet 4P/4MP Front (;ontrol Panel 3-12 LaserJet 4P/4MP Menu Map 3-14 Service Mode Menu Map (LaserJet 4ML/4P/4MP) -3-16 LaserJet 4L Self Test Page 3-20 LaserJet 4MP Service Mt]de Self Test Page 3-22 Engine Test Button and Printout (LaserJet 4L) 3-25 Service Checkpoints 4-2 Sample 5% Page Coverage 4-4 Paper Feed Area Jam 4-9 Clearing Jams from the Toner Cartridge Area 4-10 Clearing Jams from the laper Guide 4-10 Releasing Paper from the Fusing Assembly 4-11 Clearing Jams from the Fuser Area 4-12 Printer Functional Block Diagram 5-2 DC Controller Loads 5-3 Top Cover/Toner Cartridge Plunger 5-6 Power Supply Block Diagram 5-9 High Voltage Power Timing 5-11 Formatter Block Diagram 5-12 EconoMode vs. Regular Frint 5-18 Image Formation Block Diagram 5-22 Photosensitive Drum 5-23 Drum Surface Potential --5-24 Drum Cleaning 5-25 Primary Charging Roller 5-26 Image Writing 5-27 Image Development 5-29 Developing Potentials 5-30 Transferring Stage 5-3:1 Fusing Film and Pressure Roller 5-32 Printer Paper Path 5-34 Oblique Roller Paper Alignment 5-37
Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig vi
6-1 6-2 6-3 6-4 6-5 6-6 6-7 6-8 6-9 6-10 6-11 6-12 6-13 6-14 6-15 6-16 6-17 6-18 6-19 6-20 6-21 6-22 6-23 6-24 6-25 6-26 6-27 6-28 6-29 6-30 6-31 6-32 6-33 6-34 6-35 6-36 6-37 6-38 6-39 6-40 6-41 6-42 6-43 6-44 6-45 6-46 6-47 6-48 6-49
Phillips vs. Posidriv Screwdrivers 6-3 Memory Module (LaserJet 4L) 6-4 SIMM Access Panel (LaserJet 4P/4MP) 6-5 Power Access Door (LaserJet 4L/4ML) 6-6 Printer Cover Screws (Laser,Jet 4L/4ML) 6-7 Releasing the Printer Cover Rear Tabs 6-8 Control Panel Connector (LaserJet 4P/4MP) 6-9 Printer Cover Screws (Laser, Jet 4P/4MP) 6-10 Cover (LaserJet 4P/4MP) 6-11 Rear Door 6-12 Control Panel Assembly (LaserJet 4P/4MP) -6-13 Control Panel RFI Shield (LaserJet 4P/4MP) -6-14 Formatter Shield and PCA 6-15 DC Controller Connector& Switch Actuator 6-16 Gear Train Assembly 6-17 Screw Tightening Sequence Example 6-18 Main Motor 6-19 Oblique Roller Assembly 6-20 Tray Forms Size Guide 6-21 Paper Cassette Assemblies 6-22 Laser/Scanner Assembly 6-23 Fan 6-24 Power Switch Assembly (LaserJet 4P/4MP) 6-25 Paper Guide/Roller Assembly 6-26 Transfer Roller -6-27 Beam-to-Drum Mirror 6-29 Fusing Assembly 6-30 Fusing Pressure Plate 6-31 Upper Fusing Assembly 6-32 Fuser Delivery Assembly 6-33 Lower Delivery Roller 6-34 Lower Delivery Guide and Exit Sensor Flag 6-35 Fuser Connector Assembly 6-36 Upper Output Roller Assembly 6-37 Lower Output Rollers 6-38 DC Controller Assembly 6-40 Pickup Feed Roller Solenoid 6-41 Machine Screw Locations (DC Controller PCA) 6-43 Metal Backing Plate 6-44 DC Controller PCA 6-45 D-Roller 6-46 Pickup Feed Roller Assembly (side view) 6-47 Pickup Feed Roller Assembly (bottom view) 6-48 Feeder Guide Assembly 6-49 Small Media Roller Assembly 6-50 Static Eliminator Strip 6-51 Toner Cartridge Lever Assembly 6-52 Top Cover Switch {Plunger Assembly) -6-53 Releasing the Side Tabs 6-.54

Product Information Identification

Identification

Model and Serial Numbers
The model number and serial numbers are listed on identification labels located on the rear of the printer. The model number is alphanumeric, such as C2003A for the HP LaserJet 4L. The serial number contains information about the Country of Origin, the Revision Level, the Production Code, and production number of the printer. The rear labels also contain power rating and regulatory information as shown in Figure 1-1.

Figure 1-1

Sample Model and Serial Number Labels
Product Information Specifications

Specifications

Table 1-1 Printer Dimensions LaserJet 4L/4ML (C2003A/C2015A) 36 cm (14,25 in.) 137 cm (14.5 in.) , 116.5 cm (6.5 in.) LaserJet 4P/4MP (C2005A/C2040A) 40 cm (15.75 in.) 139 cm (15.5 in.) cm (7 in.)
Dimension Width Depth Heiaht

Table 1-2

Performance CATEGORY

Print Speed *

SPECIFICATION
Up to 4 pages per minute Up to 8000 pages Approximately lApproximately 3000 pages 34 seconds
Monthly Usage (Duty Cycle) Life Expectancy of toner cartridge** I First Print
*Actual speed depends on data complexity and software handling efficiency. **Toner Cartridge life can be extended by using EconoMocle.

Table 1-4

Electrical Specifications WATTS (typical)
VOLTS 120 Vact10% 100 Vac ? 10% 220 Vac f 1O% 240Vac k 10%
FREQ 50/60 Hz k 2 Hz 50/60 Hz? 2 Hz 50/60 Hz+ 2 tiz 50/60 Hz k 2 Hz

AMPS* 36 ,8

4L14ML

4P14MP

*Operating current requirements.

Table 1-3

Environmental
Specifications temperature: 10 C to 32.5 C (50 F to 90.5 F) Iumidity: 20-80% (no condensation) temperature: -20 to 60 C (-4 to 140F) Iumidity: 15-90% (no condensation) 4L 4P 4ML 4MP
Operating Environment Storage Environment (not including toner cartridge) Acoustic Emissions Operation position (per ISO 9296, DIN 45635,T.1 9): Printing

Standby LPA dB(A)

<48 <22

<49 <33

<51 <22

<49 <31

LPA dB(A)
Bystander 1m (per ISO 7779, DIN 45635,T.1 9): Printing Standby

Sound Power

<45 <22 <5.9 <3.5

<46 <30

<47 <22 <6.1 <3.6
<46 <29 <6.0 <4,4
LPA dB(A) (per ISO 9296): LPA dB(A) LPA dB(A)

Printing Standby

<6.0 <4.4
Product Information Product Overview

Product Overview

External Assembly Locations (LaserJet 4L/4ML)

Figure 1-2

External Assembly Locations, Laserdef 4L/4ML

Basis Weight

Paper Cassette: 16 to 28 pound (60 to 105 g/m2). Manual Feed Slot: 16 to 36 pound (60 to 135 g/m2).* Cut sheet to within 0.3 inch (0.8 mm) of nominal, 0.20 square. 100% chemical wood pulp and/or cotton fiber. Long grain. 4,7 *I% by weight. moisture proof ream wrap.

Finishing Precision

Furnish (Composition) Grain Moisture Content Packaging Smoothness

Polylaminated

100 to 250 (Sheffield)*
* LaserJet 4P/4MP only Heavier paper stock, in the range of 36 to 42 pound (135 to 158 gid) may be used, but must use the flat paper path (manual feed, rear output) and have a Sheffield smoothness rating not greater than 180.
The flat paper patlf (manual feed slot and rear face-up delivery door) is recommended for envelopes, overhead transparencies, and labels.

Envelope Specifications

Choose envelopes that are well-constructed. They should lay flat and be sharply creased. They should not be wrinkled, nicked, or otherwise damaged. Envelopes with a peel-off adhesive strip, or more than one fold-over flap to seal, must use adhesives compatible with the heat and pressure of the printers fusing process. When printing envelopes, always use the flat paper path ~manual feed siot and the rear face-up delivery door). To prevent severe printer damage, do not use envelopes having windows, clasps, snaps, or synthetic materials.

TaMe 2-5 Paper

Envelope
Paper used for envelope construction must meet the requirements in the table under Media Selection Guidelines. 20 to 24 pound (75 to 90 g/m2), single thickness 3.3 to 5.5 roils (0.084 to 0.14 mm), single thickness Envelopes must lay flat with no more than 0.2 in. (5 mm) curl across the entire surface. Envelopes must not have any adhesive exposed to the printer. They must be folded accurately, within f 0.04 (1 mm). There must be no more than two thicknesses of paper anywhere along the leading edge. All folds must be well scored and sharply creased, and construction must be tight (not baggy). Envelopes must not be stuck together with excess seam sum. 1100% chemical wood pulp and/or cotton fiber. Must not scorch, melt, offset, or release hazardous emissions when heated to 392 F (20V C) for 0.1 second, Long grain. 4.7 +1% bv weiaht. 1100 to 250 (Sheffield)
Basis Weight Caliper Curl (Pre-printed) Finishing
Furnish (Composition) Fusing Compatibility Grain Moisture Content Smoothness

Adhesive

Label Specifications

when selecting labels:

Use the following guidelines
The top sheet (printing surface) must be of copier quality and provide good toner adhesion. The carrier sheet (backing sheet) must be compatible with the temperatures and pressure of the fusing process, and must be coated for easy release of the top sheet. The adhesive must be stable at the 392 F (200 C) temperatures encountered for 0.1 second in the printers fusing process, and must not produce emissions that exceed exposure levels or threshold limits established by OSHA and other safety agencies. Adhesives must not come into direct contact with any part of the printer. Labels must be arranged on the carrier sheet so that any exposed spaces run lengthwise down the sheet. Using label stock with spaces between the horizontal rows of labels can often result in labels peeling off during printing, causing serious jamming and possible printer damage. wide selection of suitable labels is available through Hewlett-Packard. A list of available sizes is in the HP LaserJet Printer Family Paper Specification Guide, HP Part No. 5002-1801. See Chapter 1 for ordering information, or contact your local authorized HP dealer. Do not attempt to print on label sheets after any of the labels have been removed from the sheet. Damage to the printer may result.

m ****8****

EconoMode HP Explorer

Univers tvld
Af)tlCme Ohre Aatiaue Olive Bd Antkwe Olive It Albems Md Albertus XBd Wingdng3 rsd%l%~%c

LmR.4m Ehhanced PCL 5

W L!3TBR OFF Mmmn.i LTo AUIO OFF OFF 12.0 10.0 EO!.(AN8

3 &

Bi-Tronics * Ii!!51

RAM s;,.

POW,* P.9gc Cmmk F)rmvm, Datcmdc : IWO Adapt Uti COtml Errors

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15520927 No None

Figure 3-6

LaserJet 4L Self Test Page (showing default settings)
Installation and Configuration Printing a SM Test
The LaserJet 4L Self Test Fields
1. Printer Features List. This area can be used to check for graphics print quality. 2. Scalable Typeface List. Samples of the printers internal scalable typefaces. hlaa

Removing

to facto~-default
ac power returns items 3 through 12 settings (shown in Figure 3-6).

3. Paper Handling.

Shows the current paper settings. Current settings for print density (REt).
4. Print Quality Adjustment. and Resolution Enhancement
5. Memory Configuration. Settings for Image Adapt, Page Protection, and Auto Continue. 6. EconoMode. Setting of this toner-saving feature.

7. Font Selection.

Current default printer font settings.
8. RAM size. Shows the total amount of installed printer memory, including added optional memory. Use to verify proper memory installation. 9. Page Count. Shows approximately how many pages have been printed since the last power on. This value is returned to zero whenever the printer is powered off. 10.Firmware Datecode. Shows the datecode of installed firmware in YYYYMMDD format.
11. Image Adapt Status. Displays YES if the Image Adapt data compression feature has been invoked since the last power on. 12. Control Errors. Shows the number of 1/0 or misprint errors since the last power on.
Installation and Configuration Pining a sell Test
.= $ERVICE MENU PAGES CR PAPER SKIP DEMO !31AGNOSTICS ~

= lF1lER = FALSE = OFF

Pm ,.fig m.,,. PRINTING MENU COPIES = 3 PAPER - LETTER ::;:NTAT IO!. : :ol POrr$it ~ FEm. OFF = ,fDlw

.-m-..

1 PCL MEMU can mm FWT WBER PITCH SW SE7 : : <1.-.1) = 10.00 = RCMAM 8

Ps E vu m, P* ,,,s

JOB MENU ,MEDROT ECT RESWJTIDM PERSONAL V T ,SOUT SERIAL WI!.U SFXIAC P,C 1NC mm RAW m POLARITY

: $~:0

WNFIG MEMU m WARN AUID cCW ,,, s,,,

~ : = 3

PMALIE L MENU HI, S.EED #lW FI:TNS

= ES = ON

. = = -

R.-232 El RIO* 96C+ nr

TE$T MEW ,,,, ,,,, Law SELF TEST PC1 lVPE 11ST ,,, mm PA.f m.W, !, m,.,
,$ TWf FACE L 1S1 ,S DEMO PAGE
Installation and Configuration Printing a Self Test
The LaserJet 4MIJ4P/4MP o

Developing

The developing station develops the latent electrostatic image into a visible image on the drum. The developing unit consists of a metallic cylinder that rotates around a freed magnetic core inside the toner cavity. Toner is a powdery substance made of black plastic resin bound to iron particles, which is attracted to the magnetic core of the cylinder. A rubber blade brushes the toner on the developing cylinder to a uniform thickness. The toner particles obtain a negative surface charge by rubbing against the developing cylinder which is connected to a negative dc supply. The negatively charged toner is attracted to the discharged (grounded) areas of the drum exposed to laser light, and repelled from the negatively charged (non-exposed) areas. An ac potential is applied to the developing cylinder to decrease the attraction between the toner and the magnetic core of the cylinder, and to increase the repelling action of toner against the areas of the drum not exposed to laser light. This ac potential improves density and contrast (see Figure 5-14).

cylinder

AC bias DC bias

F,.--.,

i-qure

nnage ueveloprnenl

The dc bias of the developing cylinder is adjusted to change the force of attraction between the toner and drum by changing the print density setting (from the front panel or through software). A change in dc bias causes either more or less toner to be attracted to the d~um, which in turn either increases or decreases the print density. The print density variation is approximately t 10% (see Figure 5-15). Both the primary and developer dc bias voltages are changed in response to the density setting.
Developing cylinder surface potential f +V -0
2 % s ~ -v -----------------. --:--------------. --- /

Drum surface potential

(exposed area)
--ocbias \ Drum surface potential (unexposed area)

Time t

Figure 5-15

Developing Potentials

Transferring

At the transferring station. the toner image on the drums surface is transferred to tfie paper: A positive cha~ge applied to the back of the paper by the transfer roller causes the negatively charged toner on the drums surface to be attracted to the page. The small radius of the drum, combined with the stiffness of the paper causes the paper to peel away from the drum. The Static Eliminator also helps separate the paper from the drum. The Static Eliminator weakens the attractive forces between the negatively charged drum surface and the positively charged paper. Without this help, thin paper can wrap around the drum. After separation, the paper moves to the fusing station and the drum rotates to the cleaning and conditioning stations.

Figure 5-16

Static charga Jf eliminator Tranafer charging roller I

Fusing Stage

At the fusing station, the toner is fused into the paper by heat and pressure to produce a permanent image. The paper passes between a ceramic heating element protected by a thin, Teflon sleeve and a soft pressure roller. This melts the toner and presses it into the paper. The ceramic heating element comes up to fusing temperature very quickly, and thus does not require any power while the printer is on STANDBY. These are the first Hewlett-Packard LaserJet printers to employ this instant-on fusing system. Other laser printers use a halogen heating lamp and require frequent warming to maintain a minimum standby temperature. This feature saves power while virtually eliminating the warm-up period. The fusing temperature is monitored by the DC Controller PCA, using a thermistor (TH901). The DC Controller maintains a temperature of about 180 C during print mode. If the fusing svstem overheats (about 215 C), a relay o~ens the Dower circuit to the fusing heater, causing a Fuser Erro~ message. if the fusing system exceeds 240 C, the thermal fuse will open, cutting off power to the fuser.

9---!3/:::::,,,.,.,

Toner./. \ Paper Pressure Roller -. ,
-. Fusing Film and Pressure Figure 5-17

Roller

Paper Feed System
The following topics are discussed in this section: Paper Movement Solenoids Photosensors Paper Out Sensor Input Paper Sensor Printing from the Paper Cassette Printing from Manual Feed Paper Jam Detection Overview
Functional Overview Paper Feed System

Paper Movement

The paper feed system picks print media automatically from the paper cassette or accepts it from the manual feed slot and delivers it to the image formation system at precisely the right time. The system then feeds the media to the fusing station, and delivers the finished nroduct to the outmt ~osition. either the face-down. output tray on top of the printer, or through the face-up delivery slot at the rear of the printer. The output path is user-selectable by turning the paper path knob on the rear of the printer. Figure 5-18 shows the possible paper paths and locations of the various solenoids, photosensors and rollers.

1. Open the Memory Door. 2. Pull outward on the small handle to unplug the memory assembly and remove.

Figure 6-2

Removing the Memory Module (LaserJet 4L)

Memory/Language

SIMMS (LaserJet 4P/4MP)
The SIMM slots are under an access panel on the left side of the printer. Place the printer on a firmly supported, flat surface. 1. Push downward forcefully on top of the access panel to release its clips from the main Printer Cover (Figure 6-3, callout 1). 2. Remove any SIMM modules (release side clips, tilt upward and lift out carefully). SIMM modules must be removed prior to removing the Printer Cover to avoid damage.

clAL!-l-lo N

Figure 6-3
Removing the SHJM Access Panel (LaswJet 4P/4NlP)
Tore-install: SIMM module can be installed in any available slot. Sequence is irrelevant. Install with the small notch toward the left. To re-install the access panel, hold it in place and lift firmly upward on the thumb grip (Figure 6-3, callout 2) to snap into place.
Removal and Replacement Cover and Doors

Cover and Doors

Power, I/O and Memory Doors (LaserJet 4L/4ML)
The Power Door is located on the right side of the printer. The I/O Door and Memory Door are on the left side (refer to Figure 1-2). Some doors are not hinged; and are removed simply by opening. Others (such as the Power Door) have a small hinge tab which holds the door in place. To remove the Power Door: 1. Open the door to a 90 degree angle. 2. Push the upper tab down slightly and tilt the door out (Figure 6-4).

Figure 6-4

Removing the Power Access Dcmr (LaserJet 4L/4ML)
Printer Cover (LaserJet 41J4ML)
1. Remove the Power Door and unplug the power cord (Figure 6-4). 2. Remove the toner cartridge and paper cassette. 3. Remove any optional memory card (Figure 6-2). Step 3 is critical to avoid darnage to the memory card, the Formatter PCA, and the DC Controller.
4. Unplug the parallel cable. 5. Remove the (4) self-tapping callout 1). printer cover screws (Figure 6-5,

Figure 6-5

Fbncwing W Prinkr flow

Screws (LaserJet 4L/4ML)

on next page)

Coverand Doors

6. With the Rear Door open, pull the lower rear tabs outward, away from the printer and lift upward slightly (Figure 6-6).

Figure 696

Releasing the Printer !XIwr Flew Tabs
7. Place a small object under the rear of the cover to keep it from snapping back in place. Pull the front lower front tabs outward, away from the printer chassis as in step 6 above. 8. Grasping the front and rear, lift the cover straight up, being careful to not catch any other assemblies while lifting. Avoid holding the cover by the more flexible left and right sides. Be careful to avoid catching the green Fuser Release Tab at the rear of the printer while lifting the cover off.

Be carefid not to lift one end of the shaft more than about 1/2 inch (1 cm) before both ends have been released, as this will break the shaft.

Figure 6-34

Removing the Upper Output Roller Assembly

Lower Output Rollers

There are four-separate output rollers located directly below the Upper Output Roller Assembly. Each roller is held in place by three pressure tabs. 1. Remove the Printer Cover. 2. Remove the Upper Output Roller Assembly (Figure 6-34). e @
3. Push either the left or right tab inward, tilt the Output Roller and lift upward to remove (Figure 6-35). Use the same procedure for all four rollers.

Figure 6-35

Removing the Lower CMpwl Rollers
Removal and Replacement Bottom Assemblies

Bottom Assemblies

The DC Controller Assembly is located on the bottom of the printer. The PCA is protected by a metal shield assembly, and is mounted to a plastic base. The Formatter PCA and Fusing Assemblies are connected directly into the DC Controller and must be removed prior to removal of the DC Controller Assembly. 1. Remove the Printer Cover, the Fusing Assembly (Figure 6-27), the Formatter Shield and PCA (Figure 6-13), and the Power Switch Assembly (LaserJet 4P14ikTP only - Figure 6-23). Failure to remove all the above components before removing the DC Controller will result in printer damage.

Cliu-r[ah!

2. Remove the (2) screws that attach the grounding Gear Train Assembly (Figure 6-36, callout 1).

springs to the

3. Remove the (5) self-tapping screws and the (1) machine screw from the bottom of the DC Controller Assembly (Figure 6-36, callouts 2 and 3). Do not remove the Pickup Solenoid screw (crossed circle in Figure 6-36). 4. Push the Pickup Feed D-Roller solenoid arm in and rotate the D-Roller down, clear of the solenoid arm (Figure 6-36, callout 4). 5. Gras~ the rails on either side of the DC Controller Assemblv and fift the assembly out, being careful not to catch the sol&oid arm on the Pickup Feed D-Roller.
When removing the DC Controller Assembly there will be resistance where the connectors are attached (on the left in Figure 6-36). A firm tug may be necessary to free the assembly.

Figure 6-36

Removing the DC Controller Assembly

2. Remove the plastic latch clip (D-Roller bushing, Figure 6-42). Use needle nose pliers to twist counter clockwise and pull it out through the access opening in the Gear Train Assembly. Be sure to remove the plastic latch clip as shown in Figure 6-41 before attempting to remove the D-Roller, or damage to the printer will result.

[c)i~]~]cliv

Figure $-42
the Pickup Feed Roller Assembly (side view)
3. Lift upward on the pressure clip on the end of the Pickup Feed D-Roller and remove the D-Roller (Figure 6-43, callout 1). This provides access to one of the mounting screws. 4. Remove the (2) self-tapping screws and lift the assembly straight out (Figure 6-43, callout 2).

Figure 6.43

Removing the Pickup Feed Roller Assembly (bottom view)
To re-instalk Rotate the Registration Roller slightly to allow the gears to mesh before seating the assembly. Do NOT force the assembly back into place. sure the gears are meshed properly before replacing screws. Be

Feeder Guide Assembly a

and High Voltage Shield
1. Remove the Printer Cover, the Fusing Assembly (Figure 6-27), the Formatter Shield and PCA (Figure 6-13), the Power Switch Assembly (-LaserJet 4P/4&lP only- Figure 6-23), and the DC Controller Assembly (Figure 6-36). 2. Remove the (2) self-tapping screws and the (1) machine screw from the Feeder Guide (Figure 6-44, callouts 1 & 2). 3. LaserJet 4P14MP: Push the power switch grounding strap outward to provide clearance (Figure 6-44, callout 3). 4. Tilt the right edge (opposite the Toner Cartridge Lever) up first, then lift carefully up and toward the right to remove. CA LJTION LaserJet 4P/4iWP: Carefully free the Small Media Roller drive shaft before lifting upward to avoid damage (Figure 6-44, callout 4).
Tore-install: LaserJet 4P/4MP: Carefully align the Small Media Roller drive shaft (Figure 6-44, callout 4) before installing the Feeder Guide.
Small Media Roller Assembly
1. Remove the Printer Cover, the Fusing Assembly (Figure 6-27), the Formatter Shield and PCA (Figure 6-13), the Power Switch Assembly (LaserJet 4P/4MP only--Figure 6-23), the DC Controller Assembly (Figure 6-36), and the Feeder Guide Assembly (Figure 6-44). 2. Turn the Feeder Guide black side up and remove the (1) screw from the Small Media Roller bracket (Figure 6-45, callout 1). Remove the bracket and drive shaft with the attached gear. CAUTION The drive shaft is lubricated. Be careful not to contaminate the lubricant when handling.

Table 7-3

Door Open Error LaserJet 4P/4MP Display Panel Description & Recommendations
LaserJet 4L/4ML LEDs $m ma ~m D o= Error light is on steady. All other lights are off.
12 OPEN OR NO EP 1. Printers Top Door is open andior the toner cartridge is missing or not installed properly. Reinstall toner cartridge and close door. 2. Part of the Top Door that pushes the plunger down is broken. Replace the Top Door, 3, Top Door Switch (Plunger Assembly) is broken. Replace (see Figure 7-3). 4, Toner Cartridge Lever Assembly is broken, Replace the Assembly, 5, Faulty Microswitch SW201 (Top Door Switch) on the DC Controller PCA, Replace DC Controller PCA.

Top Door Microswitch

(SW201

Switch

Figure T-3

Top Door/Toner cartridge

Plunger and Lever Assembly

, Troubleshooting

Table 7-4 LaserJet lL/4ML LEDs
Memorv Error LaserJet 4P/4MP Display Panel 20 MEM OVERFLOW 21 PRINT OVERRUN 22 ERROR Description & Recommendations
ror light is inking, and I other lights e off.
1. Too much data, or data too complex. Turn Page Protection ON or to AUTO (can be set within HP Explorers Remote Control Panel). 2. Add optional memory. 3. Reduce the complexity of the print job. LaserJet 4P/4MP: Press ~ resume r)rintina. to

Table 7-5

Manual Feed
LaserJet 4P/4MP Dis~lav. Panel.
Data light is blinking, and all other lights are off,
AF FEED [paper size] 1, Insert paper into the manual feed slot. AE FEED[env. size] This will fulfill the manual feed request. 2, To avoid manual feed on this job, press the front panel button to override the manual feed request and to feed paper from the paper cassette. 3. To avoid manual feed on future jobs, go into a software application or the HP LaserJet Explorer to change the setting from Manual Feed to Paper Cassette feed.
Service Errors Service Errors inhibit further operation of the printer until some
action is taken. LaserJet 4L/4ML
All lights will turn on in a steady state. Pressing and holding the front panel button will reveal a pattern on the lights. (The error pattern will only be displayed as long as the front panel button is held down.) Use this pattern and the corresponding reference in Tables 7-6 through 7-15 to identify what type of service error has occurred. LaserJet 4P/4MP
Service messages are displayed on the front Control Panel in the same manner as all other messages. No action is required to display further error codes. Table 7-6 Service Error LaserJet 4P/4MP Display Panel Not Applicable (LaserJet 4L14ML Only) Description & Recommendations
All four lights on (without pressing the front t3anel

~lca QDI C)m

Install the toner cartridge, and close the Top Door. The start-up sequence should rotate the drum enough to move the mark. Open the printer, and inspect the gear that was marked in step 3. Verify that the mark moved.
If the mark did not move, inspect the gear train to ensure that it is meshing with the toner cartridge gears. If the printers drive gears appear functional, and the drum does not move, replace the toner cartridge. This test is especially important cartridges have been used. if refilled toner
Troubleshooting High-Voltage Power Supply Check
High-Voltage Power Supply Check
The High-Voltage Power Supply circuitry, on the DC Controller PCA, provides the necessary voltages for the printers electrophotographic processes. A method for verifjring the high-voltage system is given in the table below. Table 7-34
l-ligh-Voltage System Checks
CHECKS 1, Toner cartridge connection points.
ACTION Visually inspect the three connection points on the underside, right end of the toner cartridge. If they are dirty or corroded, clean the connections. Clean using alcohol only. If damaged, replace the toner
2. High Voltage Connector Assembly,
The High Voltage Connector Assembly mounts on the DC Controller PCA and uses spring-loaded pins to contact the toner cartridge (see Figure 7-2 for locations). Verify that the pins are not dirty or corroded, and that the spring-loading action is functional. If the pins are dirty, clean using alcohol only; if damaged, replace the High Voltage Connector Assembly (see lC~apter 6 ~or procedure). -

Paper Curl

Paper curl is inherent to the laser printing processes, and occurs when paper is subjected to heat. Paper curl tends to relax as the paper cools while resting on a flat surface. The specification for maximum paper curl when the paper is lying flat before print is 5 mm (0.2 inches). Although paper curl cannot be totally eliminated, some steps can be taken to lessen its impact, as suggested in the following table. Table 7-35 Causes of Paper Curl RECOMMENDED ACTION

POSSIBLE CAUSE 1. Paper Path

2. Paper Surface

Try using the face-up paper delivery slot to shorten and simplify the paper path. The recommended printing surface of the page is usually marked on the end of a ream of paper, indicated by a small arrow and the phrase print this side first Load paper in the Paper Cassette with the recommended printing surface facing down Jfacing up in the manual feed slot). Over time, paper assumes the characteristics of its storage environment (in a humid environment, paper absorbs moisture; in a dry environment, paper loses moisture). Paper with higher moisture content will tend to curl more. Evaluate the storage conditions of the paper. Ail paper is manufactured differently (different textures, moisture content, drying processes, composition, etc.). Change the type of paper being used and re-evaluate the paper curl results.
3. Paper Storing and Handling

4. Paper Type

Troubleshooting Adjustment Procedures

Adjustment Procedures

Leading Edge Adjustment
The distance from the leading edge of a sheet of paper to the beginning of the printable area can be adjusted using VR301 located on the DC Controller PCA. Leading edge is set at the factory for new units and only needs adjustment when the DC Controller is replaced. VR301 can be accessed without removing any printer assemblies (other than the paper cassette). 1. Run a printer engine test (see Engine Test earlier in this chapter). Measure the leading edge distance (see Figure 7-7). If the distance is 1.5 to 2.5 mm, no adjustment is necessary. 2. If adjustment is needed, remove the paper cassette from the printer by sliding it all the way out. 3. Locate the access hole for VR301 (see Figure 7-7). 4. Turn VR301 clockwise to decrease the leading edge distance, or counter-clockwise to increase (see Figure 7-7). 5. Replace the paper cassette and run another test to compare. 6. Repeat 1 through 5 until the leading edge is within tolerance.

Leading edge of paper

t2m. * {+/0.5mm)

Figure 7-7

Mirror Adjustment
The mounting for the Beam-to-Drum mirror has an adjustment on the right end to correct for potential image skew problems. The mirror is adjusted at the factory for new units, but can lose its -setting if the mirror is removed for any reason, or if the adjustment screw has been loosened. To adjust the Beam-to-Drum Mirror:
1. Run a test print (an Engine Test, described earlier in this chapter, or another self test print, described in Chapter 3). 2. Use a pencil or pen to draw a horizontal line across the top of each vertical line on the test print image (see Figure 7-7). 3. Place the edge of a tool with an exact 90 degree corner (such as a drafting triangle) along the leftmost vertical line of the test print image, and draw a second horizontal line across the top of the page. 4. Measure the error between the lines drawn in step 2 and step 3 (see Figure 7-8). If the distance is greater than 1.5 mm, then adjustment is needed. 5. On the right end of the mirror assembly, note the current adjustment setting (if necessary, make a mark on the printer body and/or adjustment scale), and loosen the adjustment screw. 6. Shift the mirror toward the front of the printer to move the image up on the right, or toward the back of the printer to move the image upon the left. 7. Run another test print, repeating the above steps until the image skew is within tolerance.

Index-2

Irick?x
front panel button clearing error states 3-10 overview 3-9 resuming after memory error 3-10 usage table 3-11 functions, basic printer (theory) 5-2 fuser error (50 SERVICE) 7-12 fuses, DC Controller 6-42 Fusing Assembly 6-30 fusing stage (theory) 5-32 G Gear Train Assembly 6-17
J Japanese VCCI Statement
H half self test functional check 7-39 hardware, common 8-4 help labels 3-6 help labels installation 3-6 high speed, parallel I/O (theory) 5-14 High Voltage Connector Assembly 6-42 high voltage distribution (theory) 5-11 high-voltage power supply check 7-41 HP ASAP (Automated Swmort Access Program) 1-20 HP AUDIO TIPS 1-21 HP Explorer drivers disk, using 3-8 HP FIRST (Fax Information Retrieval Support Technology) 1-20
L laser and scanner drive (theory) 5-5 laser statement, Finland 1-12 Laser/Scanner Assembly 6-23 leading edge adjustment 7-43 LEDs 3-10 left side assemblies 6-15-6-29 life expectancy of consumables 4-3- 4-5 lights, room (flickering effect) 2-2 lights (LEDs), functions 3-10 loading the paper cassette 3-4 LocalTalk feature 1-2 LocalTalk cabling information B-4 - B-6 LocalTalk 1% (theory) 5-15 Lower Output Rollers 6-38 M Main Motor 6-16 main motor error (57 ERROR) 7-15 main motor (theory) 5-7 main wiring diagram 7-47-7-48 maintenance 4-1-4-12 Manual Feed mode control panel message 3-10 manual feed printing (theory) 5-38 Material Safety Data Sheet (MSDS) 1-14 matrix, printer features 1-2 media selection guidelines 2-10 media specifications 2-8-2-16 memory configuration 3-21 Memory Door 6-6 memory enhancement technology (MEt) (theory) 5-19 memory error control panel message 3-10 memory management (theory) 5-19 memory upgrade 6-4 when needed 3-10 memory, standard & optional 1-2 memoryflanguage SIMMS 6-5 menu of resets 3-27 monthly usage 1-2 motors (theory) 5-7 MSDS 1-14 N non-volatile memory (NVRAM) (theory) 5-14 NVRAM error (68 ERROR) 7-12 NVRAM Reset 7-17
UO Door 6-6 identification, printer 1-3 Image Adapt (theory) 5-20 image formation (theory) 5-22-5-32 troubleshooting 7-19-7-35 image skew adjustment 7-44 indicator lights 3-10 Input Paper Sensor, PS 1 (theory) 5-36 Input Paper Sensor Arm 6-56 input trays 1-2 intelligent on/off (theory) 5-10 installation and configuration 3-1-3-30 help labels 3-6 power cord 3-5 printer 3-2 -3-8 printer drivers 3-7 toner cartridge 3-3 interface cables, attaching 3-4, B-4 - B-6 internal assemblies 6-23-6-29 internal assembly locations 1-8

Index-3

Oblique Roller Assembly, Front 6-20 operating environment 2-2 operating requirements 2-1-2-16 optional printer memory 3-10 ordering consumables 1-17, 8-3 parts 1-17, 8-2 related documentation 1-18 overcurrent protection (theory) 5-10 overhead transparency specs 2-15 ozone emission 1-14
Control Panel (LJet 4P/4MP) 6-13 DC Controller 6-43 Formatter 6-15 PCE 1-17,8-2 performance specifications 1-4 phone numbers CIC (Customer Info Center) 1-21 consumables 8-3 CSC (Customer Support Ctr) 1-21 DMO 8-3 PCE 8-2 PDO 8-2 P printer drivers 3-7 Pacing, serial I/O (theory) 5-15 technical assistance 1-20-1-22 page count (LaserJet 4P/4MP) 3-17 photosensitive drum (theory) 5-23 page coverage, 5% 4-4 photosensors (theory) 5-35 page protect 3-10 Pickup Assembly 6-47 page protect (theory) 5-20 Pickup Feed D-Roller 6-46 paper and envelope sizes 2-9 pickup jams (theory) 5-39 paper capacities 1-2 Pickup Solenoid 6-41 Paper Cassette Assembly 3-4,6-21 pin configuration paper cassette empty parallel B-2 control panel message 3-10 serial B-3 paper cassette loading 3-4 PJL Overview (theory) 5-21 paper cassette, printing (theory) 5-37 Plunger Assembly, Top Door Switch 6-53 paper curl 7-42 power cord 3-5 paper feed area, paper jams 4-9 Power Door 6-6 paper feed system (theory) 5-33-5-39 Power Switch 6-25 Paper Guide/Top Oblique Roller 6-26 power system (theory) 5-3-5-11 paper handling 3-21 power-on jams (theory) 5-39 paper jam detection (theory) 5-39 print capacity, toner 4-4 paper jams print density adjustment (theory) 5-17 clearing 4-8-4-12 print engine control (theory) 5-5 continuous, due to PS l/PS2 6-40 print media specflcations control panel message 3-10 envelopes 2-12 paper light 3-10 print quality adjustment 3-21 ~a~er motion. monitoring and control. m-int skew adjustment 7-44 (theory) 5-5 ~rint speed 1-2 paper movement, overview (theory) 5-34 print utilities l-lg paper out sensor, PS2 (theory) 5-35 printer serial number 1-3 paper output area, paper jams 4-12 Printer Covers paper path and components 7-4 LaserJet 4L/4ML 6-7 paper sensors (theory) 5-35-5-36 LaserJet 4P/4MP 6-9 paper specifications 2-10 printer dimensions 1-4 parallel cable, bi-tronics B-2 printer drivers 3-7 parallel interface (theory) 5-14 printer drivers, obtaining 3-7 parts, ordering 1-17,8-2 7-6-7-18 printer error troubleshooting Parts Center Europe (PCE) 1-17,8-2 printer features list 3-21 Parts Direct Ordering (PDO) 1-17,8-2 printer languages 1-2 parts index printer lights, fimctions 3-10 listing by name A-2 - A-8 printer space requirements 2-3 listing by part number A-9 - A-16 printing a self test 3-19-3-24 printing engine test - LJet 41J4ML 7-36

Troubleshooting Engine Test

Engine Test

The engine test print is used to verify that the print engine is functioning correctly. The Formatter PCA is completely bypassed during an engine test. This testis therefore very useful for isolating printer problems. The engine test prints a full page of vertical lines down the entire printable area, and is thus also useful for checking and adjusting registration.
Engine Test Button Location
The engine test print button(SW301) is located on the side of the DC Controller PCA (see Figure 7-2). It is accessible through a hole in the Gear Train plate.
Printing an Engine Test - LaserJet 4L/4ML
On the LaserJet 4L/4ML, the engine test button is accessible without removing the covers, through the I/O Door area on the left side of the printer. To print an engine test, use a long object (such as a pencil) to press the engine test button (see Figure 7-4). (Do not use a metal object.) A single test page is printed.

gure 7-4

Engine Test Button and Printout, LaserJet 4L/4ML
Printing an Engine Test - LaserJet 4P/4MP
On the LaserJet 4P/4MP, the printers covers and the Formatter PCA must be removed prior to printing an Engine Test. Since the covers will be removed, the printers safety interlocks must be defeated to provide power for running the Engine Test. To defeat the interlocks and set-up the printer for an Engine Test: Shield and the
1, Remove the printer cover, the Formatter Formatter PCA (see Chapter 6).
2. Install the paper cassette (with paper loaded). 3. Install a toner cartridge in the ptinter. Lay a large sheet of thick paper over the toner cartridge and Laser/Scanner Assembly to block out ambient room light (this will prevent black streaks on the printed output). 4. On the to~ of the winter, Top DoorPlunge;(sho~ use a ~iece of tape to hold down the in Fi&e 7-5). -

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even with chassis TOEIRail to defeat.)

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Figure7-5
Defealing Top Ek90r h,mgw (Law!kfi the P

4P/4MP)

5. On the rear of the Fusing Assembly, use a pencil or flat-blade screwdriver to press the flag mechanism for the Exit Paper Sensor (PS3) in just until it is about flush with the face of the fuser (see Figure 7-6). Do not push the PS3 flag in more than about 1/8 inch (3 mm). If PS3 is pressed in too far, the printer will register a power-on jam and the Engine Test will not print. If this occurs, decrease the depth of the PS3 flag, power-cycle the printer, then retry the Engine Test.
6. Plug the ac power cord into the printer. 7. Exert downward pressure on the the toner cartridge (through the light-blocking paper) while pressing the Engine Test button SW301. Use a pencil or other non-metallic object to reach through the access hole in the Gear Train plate (similar to that shown in Figure 7-4). 8. If the single page Engine Test does not print, power-off the printer, check the Top Door Plunger to be sure it is held all the way down (step 4), and adjust the depth of the Exit Paper Sensor flag as described in step 5. 7-38