HP 4 Plus Manual
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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). Note Ensure 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 clear the locator pin and the sensor arm from the sheet metal (see Figure 6-51 callout 2). 6As you flex the right side of the assembly, carefully release the (2) plastic retaining tabs on the left (Figure 6-51 callout 2). 7Slide the Assembly to the right to clear the mounts. Note When installing the Sensor Assembly, ensure the sensor flags are free through their entire range of travel. Figure 6-51 Removing the PS1/PS2 Sensor Assembly 6-61 Removal and Replacement
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 Feed Guide Assembly Accessing the High Voltage Contact Plate and Feed Guide Assembly requires prior removal of the following: •Top Cover •Right Side Cover •Left Side Cover •Paper Feed Assembly •Toner Cartridge •Fuser Assembly •Transfer Roller (continued on next page) 6-62 Removal and Replacement
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. Note Do 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 and Replacement
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