HP 4 Plus Manual

							For further information on interval dimensions, refer to the
Repetitive Defect Ruler, Figure 7-19.
Possible CauseAction
Toner Cartridge. The circumference of
the photoconductive drum is 3.75 inches
(94mm). The circumference of the
developer roller is 2 inches (51mm). If a
defect appears in the print image at
these intervals, assume the defect is
associated with the Toner Cartridge. Replace the Toner Cartridge.
Fuser Assembly. The Fuser Roller ’s
circumference is approximately
2.5 inches (63mm) for the LJ4, and 3-1/8
(79mm) for the LJ4+/5. If a defect
appears at this interval, assume the
defect is associated with the Fuser
Assembly. Clean the Fuser Assembly rollers.
Replace the assembly if necessary.
Dirty Roller. Any dirty roller along the
paper path may result in a pattern of
repetitive print image defects. Examine and clean rollers along the
paper path.
Table 7-19Repetitive Defects
Troubleshooting 7-41 
						

							Possible CauseAction
Fuser levers not in place.
(All LJ4, some LJ4+, N/A on LJ5) The Fuser Assembly has shipping levers
that must be lowered during the setup
process. See Chapter 3 for instruction on
how to lower the fusing levers.
Media. The media may not be acceptable
for laser printing. Heavy paper stock is a
common cause of smeared print and
improper fusing. Verify that the media meets
specifications as shown in the HP
LaserJet Family Paper Specifications
Guide.
Dirty Fuser Assembly. The print smears if
the Fuser Assembly is dirty. Replace the Fuser Assembly and clean
the printer.
Bent Static Teeth. If the static teeth are
defective, the print could smear prior to
the paper entering the Fuser Assembly. If the teeth are bent or defective, replace
the Static Teeth Assembly.
Worn Gears. If the drum and paper are
not moving at the same speed the
characters may smudge. Replace the Toner Cartridge.
Foreign object in paper path. Something
is smearing the unfused toner image on
the surface of the paper. Remove any foreign material. Try a new
Toner Cartridge.
Orange Packing Spacers not removed.
Some HP LaserJet 4 only. Remove Orange Packing Spacers.
Table 7-20Smeared Print/Improper Fusing 
Possible Cause
Action
Paper Path. If the paper does not move
at a uniform speed, the print image will
be affected. Characters that are either
too tall or too short (in the direction of
paper motion), are usually a result of
drive mechanism problem. Examine the paper transport rollers
along the paper path for wear. Replace if
excessive wear exists. Inspect and
replace the Toner Cartridge, Drive Gear
Assembly, Main Motor, or Fuser
Assembly as necessary.
Laser/Scanning Assembly. Wavy,
irregular-shaped characters, or irregular
line margins in the scan direction of
printing are usually a result of a defective
Laser/Scanning Assembly. Replace the Laser/Scanning Assembly.
Table 7-21Distorted Print 
7-42 Troubleshooting 
						

							Possible CauseAction
Laser/Scanning Assembly or DC
Controller PCA. Replace the Laser/Scanning Assembly
followed by the DC Controller PCA, if
necessary (see Figure 7-12 for locations).
Table 7-22Black Pages with Horizontal White Strips
Possible Cause
Action
Input/Registration Sensor (PS1). The
Paper Pickup Roller positions the leading
edge of the paper at the
Input/Registration Sensor (PS1). If this
sensor is defective it may not sense the
presence of the paper reliably (on time). Replace the Input/Registration Sensor.
Skew tolerance for the printer is 1.5mm
over 260mm page length.
Drive Gears. If any gear within the gear
drive train becomes excessively worn, or
is excessively dirty, erratic paper
movement would result, leading to image
misregistration. Closely examine the gears along the
paper path for wear and contamination.
Clean and inspect the gears. Replace
any defective gear.
Paper Tray. The paper tray may be
preventing the paper from freely moving
through the printer. Verify that the tray is loaded correctly.
Verify that the paper tray is seated fully
into the printer. Switch trays to verify that
the problem follows the tray. Replace the
paper tray.
Paper. The surface of the paper may be
too smooth for the pickup roller to move
the paper through the paper path. Change paper. Try paper known to be
good.
Paper too heavy? See  Paper Specifications in Chapter 2.
Table 7-23Image Skew  
Troubleshooting 7-43 
						

							PS5 Check (MP Tray Paper End Sensor) Functional Test 
1Make a test sheet by cutting a notch in the trailing edge of a
sheet of paper as shown in Figure 7-9. 
2Perform the set up procedures listed for the PS4 check (MP
Tray Empty Sensor) on page 7-17, and put the test sheet into
the MP tray when the display reads XX LO\bD LEG\bL.
3The self test print should stop 2 to 5 mm above the notch (see
Figure 7-9). 
4Print that extends into cut out area indicates that the sensor
PS5 is not free in its travel or is defective.  Ensure that the
sensor lever is free throughout its entire range of travel.  If
not, replace the lever or the sensor itself.
Possible Cause Action
PC tray Microswitches. The paper tray
microswitches indicate the paper size of
the installed tray. This information is used
to format the print image to the size of
the paper installed in the tray. If the paper
tray microswitches are defective, the
image is formatted incorrectly. Perform the 
“Cassette Size Switches
(SW603, SW604, SW605) Functional
Check ” on page 7-15. Ensure that the
correct envelope size is selected if
appropriate.
PS 5 is defective. PS 5 senses the
trailing edge of the media being fed from
the MP tray. If improperly sized images result from
printing from the MP tray, check that PS
5 is functioning correctly mechanically
and electrically. This feature allows
odd-sized media to be printed with the
MP tray. Troubleshoot PS 5 as shown in
the following procedure.
MP Paper Size is not set correctly. Use the MP Paper Size Button on the Front Panel to correctly configure paper
size for the MP Tray.
Table 7-24Improperly Sized Image  
7-44 Troubleshooting 
						

							Figure 7-9 PS5 Test Sheet
Troubleshooting 7-45 
						

							Possible CauseAction
Dirty Primary Charge roller. Change the Toner Cartridge.
Bad Toner Cartridge. Replace the Toner Cartridge.
Incompatible media. During media
manufacture, inks, or other finishing
processes may interfere with the
electro-photographic or fusing process. Change type of media.
Table 7-25Vertical Dark Streaks 
Possible Cause
Action
Defective laser shutter. Check the laser shutter for free operation
when inserting the EP Toner Cartridge.
EP Cartridge Support damaged,
improperly positioned, or missing. Refer to item 4 in Figure 8-4a.  Guide
must be installed properly above the EP
Cartridge, between the laser shutter
opening and the fuser stop plate.
Bad transparencies. Transparencies
exhibit this problem if they are not
designed for proper toner adhesion. Use Hewlett-Packard-approved
transparencies (refer to the 
HP LaserJet
Family Paper Specifications Guide) .
Bad paper lot. The surface of the paper
may be too smooth for proper toner
adhesion. Try a known good paper from a reliable
source (refer to the 
HP LaserJet Family
Paper Specifications Guide ).
Poor fusing. Toner may not be fused
properly to the media. Try a known good paper from a reliable
source (refer to the 
HP LaserJet Family
Paper Specifications Guide ).
Print image fusing may not occur
correctly. Replace Fuser Assembly (see Figure
7-11 for location).
Wet paper. The paper may be damp. Try a new batch of paper. Store the paper in a dry area.
Transfer roller is dirty. Replace the transfer roller.
Table 7-26Large Print Voids 
7-46 Troubleshooting 
						

							Possible CauseAction
Defective Toner Cartridge. The Toner
Cartridge may be internally damaged. Replace the Toner Cartridge.
Bad paper lot. The paper moisture
content, conductivity, or surface finish
may be incompatible with the
electro-photographic process. Try a different paper lot (see the 
HP
LaserJet Family Paper Specifications
Guide ) for paper specifications.
Print density set incorrectly. If the print
density is set incorrectly, background
scatter can result, particularly with
envelopes. Adjust the print density. 
Inside of printer dirty. If toner dust leaked
out of the EP Toner Cartridge, this
problem can occur. Clean the inside of the printer.
Table 7-27Background Scatter 
Troubleshooting 7-47 
						

							Possible CauseAction
Defective laser shutter. Check the laser shutter for free operation
when inserting the EP Toner Cartridge.
EP Cartridge Support damaged,
improperly positioned, or missing. Refer to item 4 in Figure 8-4a.  Guide
must be installed properly above the EP
Cartridge, between the laser shutter
opening and the fuser stop plate.
Toner Cartridge. No toner is available for
print. Remove sealing tape or replace the
Toner Cartridge.
No Transfer Roller voltage. Without
transfer charge roller voltage, toner
cannot be attracted from the surface of
the drum to the paper. Perform the 
“Half Self Test Functional
Check ” which follows to check all other
electro-photographic processes.
No Developing Bias. With no Developing
Bias charge, toner is not attracted to the
drum. Refer to 
“High Voltage System Checks. ”
No drum ground path. With no ground
path the drum cannot discharge. The
negative charge on the drum repels
toner, and leaves a white page. Refer to 
“High Voltage System Checks. ”
Bad Laser Scanning Cable Assembly.
Low-level signals exchanged between
the Laser/Scanning Assembly, and the
DC Controller may be affecting laser
output. Replace the Laser/Scanning Cable
Assembly.
Table 7-28White or Blank Pages
7-48 Troubleshooting 
						

							Image Formation Troubleshooting
Half Self-Test Functional Check  
The electro-photographic process can be subdivided into the
following stages: 
•Cleaning (Physical and Electrostatic).
•Conditioning (Primary Charge Roller).
•Writing (Laser Modulation).
•Development (Formation of the Toner Image).
•Transfer (Charge to transfer the image to paper).
The purpose of the Half Self Test Check is to determine which
process is malfunctioning.  Perform the test as follows:
1Initiate an  05 SELF TEST . 
2Open or switch OFF the printer after the paper advances
halfway through the printer (the leading edge of the paper
should advance at least past the Transfer Charge roller).
3Remove the Toner Cartridge.
4Open the Toner Cartridge ’s drum shield to view the drum ’s
surface.
If a dark and distinct toner image is present on the drum ’s
surface, assume that the first four functions of the
electro-photographic process are functioning, and troubleshoot
the failure as a transfer problem.  If NO image is present on the
photoconductive drum, perform the checks shown on the following
pages.
•The Drum Rotation Functional Check.
•High voltage Power Supply Check.
Troubleshooting 7-49 
						

							Drum Rotation Functional Check 
The photoconductive drum, located in the Toner Cartridge, must
rotate for the print process to work.  The photoconductive drum
receives its drive from the Main Motor gear train.  To verify
whether the drum is rotating:
1Open the printer’s Top Cover Assembly.  
2Remove the Toner Cartridge.  Open the Toner Cartridge ’s
drum shield (cover) to view the photoconductive drum.
3Mark the gear with a felt-tipped marker.  Note the position of
the mark.
4Install the EP Toner Cartridge, and close the Top Cover.  The
1-second startup sequence should rotate the drum enough to
move the mark. Open the printer, and inspect the drum.
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 drive gears
appear functional, and the drum does not move, replace the Toner
Cartridge.
Note This test is especially important if refilled Toner
Cartridges were used.
7-50 Troubleshooting