HP 4 Plus Manual

							Electrical Overview
The block diagram in Figure A-3 shows the Duplexer electrical
components.
AC  PO WE R
SUPPLYDUPLEXER
CONTROL
PC A
AC  PO WE R
TO  PR I N TE R
INPUT
AC  PO WE R
TO  PR I N TE R
DC CONTROLLER FAN
SWITCHBACK
SOLENOID
SWITCHBACK
STEPPER MOTOR
HOLDING TRAY
STEPPER MOTOR
SWITCHBACK
PAPER SENSOR
HOLDING TRAY
PAPER SENSOR
Figure A-3 Electrical Block Diagram
Duplexer   A -5 
						

							Installing the Optional Duplexer
The optional Duplexer can be installed by the customer. There
are no fasteners securing the units together.  The printer simply
rests in place on top of the Duplexer, which, in turn, rests on top
of the optional 500-sheet Lower Cassette, if used.  
To install the Duplexer, first turn power OFF and disconnect all
cables from the printer.  Follow the steps below, referring to the
corresponding steps illustrated in Figure A-4. 
•Open the printer’s rear door and use needle-nose pliers to
release the door strap from the printer.
LJ 4 +
•Grasp the plastic retaining clip and lift it upward and
away from the door.
•Slide the door toward the left.
•Swing the right end of the door out from the printer and
slide it toward the right to free it from its hinge.
LJ 5
•Flex the rear door to release it from its hinges. (Press the
middle of the door while lifting either side.)
•Place the Duplexer on a flat surface and tilt the Switchback
Assembly partially back.
•Verify the alignment pins on the Duplexer mate with the holes
in the bottom of the printer, and if used, the top of the optional
500-sheet Lower Cassette. Place the printer on top of the
Duplexer.
•Close the rear door (Switchback Assembly) and plug in all
cables - note routing of the power cables as shown.
Note Removal of the Duplexer from the printer is the
reverse of installation - simply unplug cables,
unlatch the Switchback Assembly, and lift the
printer off the top.  If the optional 500-sheet
Lower Cassette is being used, lift the duplexer off
the Lower Cassette.
For further information, refer to the illustrated
steps in Figure A-4 on the next page. 
A -6  Duplexer  
						

							7
6
52
4 3
1
23
1
2
11
2
Figure A-4 Duplexer Installation/Removal
Duplexer   A -7 
						

							Removal and Replacement
This section describes the complete disassembly of the Duplexer.
Tasks that must be performed before beginning the procedure are
listed first. Remove the assemblies in the order listed to prevent
damage.
The assembly procedure is the reverse of the removal procedure,
except where specific instructions are provided.
In the removal and replacement procedures that follow, the
number inside the parentheses, such as (4), refers to the number
of screws to remove.
WarningPower OFF the printer and disconnect the power
cord from the outlet and the printer before
servicing the Duplexer.
Some sheet metal edges are sharp. Be careful
when working in these areas to avoid being cut.
CautionThe Duplexer contains parts that are sensitive to
Electro-Static Discharge (ESD). Always observe
proper ESD procedures when servicing the
Duplexer. 
This symbol   appears when the parts being
serviced are especially susceptible to ESD
damage. 
Required Tools
#2 Magnetized Phillips Screwdriver
Small Flat-head Screwdriver (6-inch shaft)
Needle-nose Pliers
CautionDo not use a Pozidriv screwdriver.  Damage to the
screw heads will result.
A -8  Duplexer  
						

							Removing the Covers
Removing the Switchback Covers
1Remove the (2) screws shown in Figure A-5, callout 1. 
2Lift the cover off the Switchback Assembly.
Figure A-5 Switchback Cover
Duplexer   A -9 
						

							Removing the Side Cover on Power Side
1Open the front door.
2Remove the (1) screw shown in Figure A-6, callout 1.
3Release the (3) latch points with a flat screwdriver and rotate
the cover downward (see Figure A-6, callout 2).
Figure A-6 Side Cover
A -10  Duplexer  
						

							Removing the Side Cover on Gear Side
1Remove the (2) screws on top and the (1) screw on the front
(see Figure A-7, callout 1).
2Turn the Duplexer on its side to access the latch location on
the underside.
3Release the (1) latch point with a flat screwdriver and lift the
cover off (see Figure A-8).
Figure A-7 Side Cover on Gear Side
Duplexer   A -11 
						

							Figure A-8 Latch Location on Underside of Duplexer
A -12  Duplexer  
						

							Removing the Back Cover
1Place the duplexer on a table or bench so that the back
overhangs the edge by a few inches.
2Release the (2) locating pins as shown in Figure A-9.
3Rotate the cover downward until it is free.
Removing the Front Cover
With the side covers removed, the front cover is only attached by
the holding tray arm.
1With both side covers removed, open the holding tray.
2Rotate the front cover 90 degrees to release the holding tray
arm.
Figure A-9 Back Cover
Duplexer   A -13 
						

							Removing Internal Duplexer Components
Removing the Fan/Motor/Solenoid/Sensor
Access to the electronic components of the switchback assembly is
easy once the covers are removed.  Note the location of the
switchback stepper motor (Figure A-10, callout 1), the switchback
fan assembly (callout 2) and the switchback solenoid (callout 3).
Figure A-10 Switchback Assembly - Stepper Motor Side
A -14  Duplexer