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...

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...

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...

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...

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...

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...

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....

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