HP Laserjet 4 Manual

5Release the (2) springs from the Upper Fusing Frame (see
Figure 6-48a, callout 1).
6Release the tabs that hold the Upper Fusing Frame to the
Fuser Body (see Figure 6-48a). Rotate the Upper Frame
backwards to release and access the Thermistor (see Figure
6-48b, callout 1).
(continued on next page)
 
Figure 1-48a Upper Fuser Frame Removal (LaserJet 4)
6-57 Removal and Replacement 

7Remove the (1) screw that holds the Thermistor (see Figure
6-48b, callout 2).
NoteEnsure the thermistor cable is routed correctly
when assembling the fuser (see Figure 6-47).
Figure 1-48b Upper Fuser Frame Removal (LaserJet 4 Plus)
6-58 Removal and Replacement 

Paper Control PCA Removal
1Remove the Right Side, Top, Left Side, and Font Door Covers,
then Paper Feed Assembly.
2Disconnect the cables from the sensors (see Figure 6-49,
callout 1). 
3Remove the (2) self-tapping screws from the Paper Control
PCA (see Figure 6-49, callout 2).
4Release the (5) latches that retain the Paper Control PCA (see
Figure 6-49, callout 3).
Figure 1-49 Paper Control PCA Retaining Screws and
Latches
6-59 Removal and Replacement 

Sensor PCA Removal
1Remove the Right, Left, Top, and Font Door covers. You need
not remove the MP Tray. 
2Perform the Paper Control PCA removal procedure, as shown
in the preceding section.  
3Disconnect the connectors for SL1, SL2, and M2 from the left
end of the Sensor PCA.
4Release the (3) clips that hold the Sensor PCA cover. Remove
the cover (see Figure 6-50, callout 1).
5Remove the Sensor PCA by sliding it to the left and dropping
it down.
Figure 6-50 Sensor PCA Removal 
6-60 Removal and Replacement 

PS1 and PS2 Sensor Assembly Removal
The PS1 and PS2 sensors are located under the Paper Feed
Assembly.  
1Remove the Paper Feed Assembly and place it on a flat
surface, with the MP Tray side down.
NoteYou need not remove the MP Tray from the Paper
Feed Assembly. Use a cloth to protect the MP
Tray door from scratches.
2Remove the PC Tray Pickup Roller.
3Disconnect blue-wired connector on the bottom, (callout 1).
4Remove the center pin from the dowel post.
5Flex the right side of the Sensor Assembly to...

High Voltage Contact Plate (HVCP)
and Paper Guide Removal   
This procedure involves removing many subassemblies and
difficult disassembly processes.  Because this procedure is
complex, it is separated into three sections:
•Accessing the HVCP and Feed Guide Assembly.
•Removing the HVCP and Feed Guide Assembly.
•Replacing the HVCP and Feed Guide Assembly.
Allow plenty of time to perform this procedure, and be careful not
to damage any parts during reassembly.
Accessing the High Voltage Contact Plate and...

After removing the Fuser Assembly, remove the contact plate
from the rear of the printer, as follows:
1Remove the (1) screw from the sheet metal Guide Plate Cover.
(This screw is behind the Fuser Assembly, see Figure 6-52,
callout 1).
2Remove the Guide Plate Cover by freeing the front edge,
lifting upward, and sliding the cover out the rear of the printer.
NoteDo not lose any of the (6) rollers the Guide Plate
Cover holds in place.
(continued on next page)
Figure 6-52 Guide Plate Cover Screw
6-63 Removal...

3Remove the (6) rollers from the High Voltage Contact
Plate (see Figure 6-53 callout 1). 
(continued on next page)
Figure 6-53 Paper Guide Rollers
6-64 Removal and Replacement 

4From the front of the printer, remove the (2) black self-tapping
screws that hold the Inner Cross-member. Remove the
cross-member (see Figure 6-54 callout 1).
(continued on next page)
Figure 6-54 Cross Member Screws
6-65 Removal and Replacement 

5From the left side of the printer, remove the (1) or (2) black,
self-tapping screw(s) that holds the Left Toner Cartridge
Guide Plate (see Figure 6-55, callout 1).
6Release the guide plate latch (see Figure 6-55, callout 2).
7Remove the Laser Shutter Pivot Pin from its seat in the Left
Toner Cartridge Guide Plate (see Figure 6-55, callout 3).
These two steps (5 & 6) are required for the next stage of the
HVCP removal process.
Figure 6-55 Left Toner Cartridge Guide Plate Screw
6-66 Removal and Replacement