HP 4 Plus Manual

							If a failure occurs during this period, the following errors may be
displayed: 50 SERVICE This error occurs when the fusing roller fails to
reach the correct temperature in the required
time (see “50 SERVICE ”) in Chapter 7).
51 ERROR This error occurs when the 
BD signal is not
received by the DC controller, (see  “51 ERROR
BEA\b DETECT )”  in Chapter 7).
52 ERROR This error occurs when the scanner motor fails
(see “52 ERROR ,” Chapter 7).
Functional Overview  5-39 
						

							Print Period  
When the leading edge of the paper activates the
input/registration sensor (PS1), the DC controller forces the laser
diode ON until a 
BD signal is received. Next, the DC controller
receives a VIDEO data stream (
VDO) from the formatter.  The
DC controller translates the 
VDO data into a VIDEO OUT signal
(
VDOUT), which modulates the laser diode ON and OFF, creating
intermittent bursts of laser light which reflect off the scanner
mirror and onto the photosensitive drum to form a latent
electrostatic image. 
VDO  data is sent from the formatter for each
scan line of print data on a page, and a 
BD signal must precede
each 
VDOUT  line data received by the DC controller.
When the paper exit sensor (PS3) is activated by the leading edge
of the first page, the DC controller allows the Fusing Roller to
warmup to 183 ° C. After the last 
VDO data is sent for the last
line of print data on the first page, the formatter sends a 
PRNT
signal for the second page.
About 1.87 seconds after the first 
VDO signal is sent from the
formatter, the High Voltage PCA applies positive high voltage to
the transfer roller.
When the DC controller identifies the last line of print data on
the first page, the laser diode is forced ON and generates a sweep
beam used to adjust the laser power. After the DC controller
receives a BEAM DETECT signal (
BD) initiated by the sweep
beam, the laser power stabilizes and the sweep beam turns OFF.
The DC controller then searches for a 
PRNT  signal to begin the
second page.
When the DC controller receives the next 
PRNT  signal from the
formatter, the DC controller anticipates receiving a 
BD signal
and energizes the pickup roller clutch solenoid (PC tray-SL1, MP
tray-SL2, or lower cassette SL3) about 1.0 second before it
receives the 
BD signal, and the second page feeds from the paper
tray. Until the DC controller receives the expected 
BD signal, a
nominal positive voltage is applied to the transfer roller to
prevent toner build-up while the transfer Roller is in direct
contact with the drum.
5-40 Functional Overview 
						

							The formatter then sends VDO data to the DC controller. The DC
controller translates the 
VDO signal into a VIDEO OUT signal
(
VDOUT), which modulates the laser diode ON and OFF, creating
intermittent bursts of laser light that are reflected off the scanner
mirror and onto the photosensitive drum to form a latent
electrostatic image.  Upon receipt of a 
BD signal from the DC
controller, 
VDO data is sent from the formatter for each scan line
of print data on a page.
Before the next sheet of paper arrives, the voltage on the transfer
roller switches from the nominal standby voltage to a positive
high voltage, to prepare to transfer the toner image from the
drum to the paper. The process repeats for each successive page
as necessary.
If a failure occurs during this period, the following errors may be
displayed: 
41 ERROR This error occurs when a sheet of paper is fed too
soon or when an unstable 
BD or TOP signal is
received (see  “41.x ERROR” message in Chapter 7).
50 SERVICE This error occurs when the fusing roller fails to
rise to the correct temperature in the required
time (see “50 SERVICE ”) in Chapter 7).
51 ERROR This error occurs when the 
BD signal is not
received by the DC controller (see  “51 ERROR ” in
Chapter 7).
52 ERROR This error occurs when the scanner motor fails
(see “52 ERROR ” in Chapter 7).
Functional Overview  5-41 
						

							Last Rotation Period  
After printing is complete, the Last Rotation period begins,
during which residual static charges are eliminated from the
photosensitive drum to prepare for the next printed page.
About 1.7 seconds after the Last Rotation period begins, a
nominal standby voltage is applied to the transfer roller to stop
the toner attraction. Then, 4.0 seconds after the Last Rotation
period begins, the negative DC high voltage on the primary
charging roller is turned OFF, leaving the AC voltage to
neutralize the drum’s surface. Finally 5.98 seconds after
beginning the Last Rotation period, the transfer roller voltage
returns to a negative high voltage, and any toner on the surface
of the transfer roller is attracted to the photosensitive drum.
At the end of the Last Rotation period, the fusing roller returns to
172 ° C, the main motor turns OFF, the scanner motor turns OFF,
the AC high voltage to the primary charging roller turns OFF, the
transfer roller voltage returns to 0 volts, and the printer returns
to the Standby period. About 30 seconds after the printer returns
to the Standby period, the exhaust fan switches to low-speed
rotation.
When another 
PRNT signal is sent from the formatter, printer
operation resumes.
5-42 Functional Overview 
						

							6
Removal and Replacement
This chapter describes the complete disassembly of the printer
from the beginning. In every instance, tasks that must be
performed before beginning the procedure are listed first.
Remove the assemblies in the order listed to prevent damage
during re-assembly.  
Removal and replacement of user-replaceable maintenance items
is shown in Chapter 4, “Preventive Maintenance.” These items
include: 
•All Pickup Rollers and Separation Pad
•Transfer Roller Replacement
•Installing the Toner Cartridge
Servicing the printer involves replacing printed circuit and
electro-mechanical assemblies. Do not repair component failures
within these assemblies. In all instances, replace the failed
assembly.
The assembly procedure is the reverse of the removal procedure,
except where specific instructions are provided.
Caution Power-off the printer and disconnect the power
cord from the power outlet and the printer before
servicing the printer.
Some sheet metal edges, particularly around the
formatter cage, are sharp. Be careful when
working in these areas to avoid being cut.
NoteThe printer contains parts that are sensitive to
Electrostatic-Static Discharge (ESD).  Always
observe proper ESD procedures when servicing
the printer. This symbol:   appears in this
chapter when the parts being serviced are
especially susceptible to ESD damage.
Removal and Replacement  6-1 
						

							Required Tools
Hardware Review
All screws used in the printer are Phillips head, which require a
Phillips screwdriver.  Figure 6-1 shows the difference between a
Phillips and a Pozidriv screwdriver. Note that the Phillips tip has
more beveled surfaces.
CautionUse of a Pozidriv screwdriver will damage the
screw heads. Use Phillips only.
 
QTY
TOOL
1 #2 Magnetized Phillips Screwdriver (6-inch shaft)
1 Small Needle Nose Pliers
1 Small Flat-head Screwdriver (6-inch shaft)
1 5mm Nut driver
Table 6-1Required Tools
Posidriv
Phillips
Figure 6-1 Comparing Phillips and Pozidrive Screws
6-2 Removal and Replacement 
						

							Table 6-2 describes the screws used in the printers, and provides
guidelines to help determine where each type of screw is used.
The screws can vary in length depending on the thickness of the
material being fastened.
Typically, plated screws are used in areas visible to the customer,
and black screws are used in all other areas of the printer.
Always note where each type of screw is located and replace each
one into its original location.
CautionTo install a self-tapping screw, first turn it
counter-clockwise to align it with the existing
thread pattern, then carefully turn clockwise to
tighten. 
Do not over-tighten.  If a self-tapping
screw-hole strips, repair of the screw-hole or
replacement of the affected assembly is required.
In the removal and replacement procedures that follow, the
number inside the parentheses, such as (4), refers to the number
of screws you must remove.
DRAWING DESCRIPTION PURPOSE
Threaded Phillips screw with
lock and flat washerUsed to fasten metal or plastic
to threaded plastic or metal.
Threaded Phillips washer head
screw Used to fasten metal or plastic
to metal when high torque is
required.
Threaded Phillips w/captive
star washer Used to fasten metal to metal
when good electrical contact is
needed.
Self-tapping Phillips screw Used to fasten metal or plastic to plastic mainframes.
Table 6-2Printer Hardware Descriptions
Removal and Replacement  6-3 
						

							Removing the Covers 
Right Side Cover Removal
LJ 4/4 Plus
1Open the Top Cover and release the Right Side Cover by
pressing at the points shown in Figure 6-2.
2Fold the cover away from the printer to release the bottom
supports and lift the door off of the printer frame.
LJ 5
1Open the Top Cover and loosen the retaining screw on the
right side cover located at the upper right rear of the printer.
2Slide the right side cover back and fold the cover away from
the printer to release the bottom supports.
WARNING! Since the handle is part of the right side cover,
the retaining screw must be fully tightened or
printer damage or personal injury may result.
Figure 6-2 Right Side Cover Release Points
6-4 Removal and Replacement 
						

							Top Cover Removal 
1Open the Top Cover.
2Remove the Right Side Cover.
3Open the Rear Door.
4Remove the (3) screws shown in Figure 6-3, callout 1.
5Release the (2) latch points with a flat screwdriver while
lifting the Top Cover (see callout  2.)
6Carefully lift the top cover to access the Control Panel cable.
(continued on next page)
Figure 6-3 Front Top Cover Screws and Latches
Removal and Replacement  6-5 
						

							7Disconnect the Control Panel Ribbon Cable and remove the
top cover (see Figure 6-4).
Figure 6-4 Control Panel Cable
6-6 Removal and Replacement