HP Laserjet 4 Manual

Main Motor Assembly Removal
1Remove the Right Side Cover, Top Cover, and the Formatter
Cage Assembly.
2Unplug the Main Motor connector from the Main Motor
Assembly (see Figure 6-30, callout 1).
3Remove the (4) Main Motor screws (see Figure 6-30, callout 2).
4Remove the Main Motor.
Figure 1-30 Main Motor Assembly 
6-37 Removal and Replacement 

Gear Assembly Removal 
1Remove the Top Cover, the Right Side Cover, the Fuser
Assembly, and the Formatter Assembly.  
2Remove the Main Motor Assembly (see Figure 6-30).
3Remove the (2) screws that hold the Gear Assembly (see
Figure 6-31 callout 1).
4Slide the Gear Assembly from the rear of the printer. 
NoteBefore tightening down the mounting screws, be
sure the shoulder around the upper left mounting
screw hole on the gear assembly protrudes
through the frame.
Figure 1-31 Gear Assembly Screws (Located...

Fan Removal
NoteNote the cable routing before beginning this
disassembly procedure.  Be careful not to damage
the cables during re-assembly.
1Remove the Right Side Cover, the Top Cover, and the
Formatter Cage Assembly.
2Unplug the fan connector (J209 on the LaserJet 4, J211 on the
LaserJet 4+/5). (See Figure 6-32, callout 1.)
(continued on next page)
Figure 1-32 Fan Connector
6-39 Removal and Replacement 

3Remove the RFI shield (LJ 4 only) by releasing the retaining
tab and sliding the shield up (see Figure 6-33, callout 1). 
4Laser Jet 4: Release the (4) clips from the fan ducting to
provide clearance and remove the fan from the top of the
printer (see Figure 6-33, callout 2).
Laser Jet 4 Plus/5: Remove (1) screw on the right-rear and
release the tabs on the lower left adjacent to the Output Paper
Assembly
5Remove the fan. 
NoteWhen reinstalling the fan, verify that the air is
blowing upward.
Figure 1-33...

Output Assembly Removal
1Remove the Right Side Cover, the Top Cover, and the Left
Side Cover.
2Release the grounding strap from the left side of the frame.
3Rotate the top of the Output Assembly toward the front of the
printer while releasing the two retaining latches (see Figure
6-34, callout 1) until the locating tabs are free.  Slide the
assembly to the rear and lift it out of the printer.
Figure 1-34 Output Assembly Removal 
6-41 Removal and Replacement 

Paper Exit Sensor (PS3) Removal 
1Remove the Right Cover, Top Cover, and the Output Assembly.
2Disconnect the Sensor Cable.
3Lift the Sensor Retaining Latch and slide the sensor forward
(see Figure 6-35).
4Remove the Paper Exit Sensor.
Figure 1-35 Exit Sensor 
6-42 Removal and Replacement 

Scanner Assembly Removal
1Remove the Right Side Cover, Top Cover, Left Side Cover, and
the Output Assembly.
2Remove all cables from the Scanner retaining clips.
3Remove the (3) connectors (see Figure 6-36, callout 2). 
NoteBe careful not to flex the Laser PCA when
removing or installing the cables.  The Laser PCA
can be damaged easily.
4Remove the (4) screws from the Scanner Assembly. (see
Figure 6-36, callout 1).
5Remove the Scanner Assembly.
NoteWhen installing the Laser/Scanner Assembly,
check that...

Lower Cassette Assemblies
The field-replaceable assemblies of the Lower Cassette are:
•Lower Cassette Sensor PCA Assembly
•Lower Cassette Pickup Motor Assembly
Lower Cassette Sensor PCA Removal
1Release the Sensor PCA cover latches (see Figure 6-37
callout 1).
2Cut the tie-wrap and remove the (3) sensor connectors (see
Figure 6-37 callout 2).
3Release the catch at the bottom rear of the Sensor PCA.  (Use
a slender object like a flat-blade screwdriver.)
4Remove the Sensor PCA.
Figure 1-37 Lower Cassette...

Lower Cassette Pickup Motor Removal
1Open the sensor cover and disconnect the center and rear
connectors (see Figure 6-37, callout 2).
2Release the (2) tabs that hold the Upper Front Cover (access
the tabs through the slots with a small screwdriver - see
Figure 6-38 callout 1).  Remove the cover by rotating it toward
the front.
3Remove the (2) screws from the front and rear left side (see
Figure 6-38 callout 2).
4Remove the cables from the race channel at the front of the
Lower Cassette Base (see Figure...

5Lift the motor assembly straight up out of the the Lower
Cassette Base (see Figure 6-39).
NoteNote the ground connector underneath the Motor
Assembly. Be careful not to damage this
connector during reassembly.
Figure 1-39 Lower Cassette Motor
6-46 Removal and Replacement