HP Laserjet 4 Manual
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Electrical Overview The block diagram in Figure A-3 shows the Duplexer electrical components. AC PO WE R SUPPLY DUPLEXER 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 CONTROLLERFAN 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
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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. NoteRemoval 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
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7 6 52 4 3 1 23 1 2 11 2 Figure A-4 Duplexer Installation/Removal Duplexer A -7
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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
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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
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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
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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
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Figure A-8 Latch Location on Underside of Duplexer A -12 Duplexer
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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
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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