HP 4 Plus Manual
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Replacing Fuser Assembly Parts The following procedures describe the removal and replacement of major Fuser Assembly Components (Fusing Roller, Thermistor, Thermoswitch, and Heater Lamp). When performing these procedures, note the order in which the parts were removed and their orientation. CautionHandle the Heater Bulb by the ceramic ends. Do not touch the Heater Bulb, or allow it to become contaminated. If contamination occurs, clean the bulb thoroughly with isopropyl alcohol. 6-47 Removal and Replacement
Fuser Assembly Configuration Figure 6-40 provides an overview of the orientation of the major Fuser Assembly components. Before beginning the fuser disassembly procedures, become familiar with the location and orientation of the various Fuser Assembly parts (see Table 6-1). Figure 1-40 Fuser Assembly CalloutAssembly CalloutAssembly 1 Exit Sensor Flag 5 Fusing Roller 2 Thermistor 6 Plug to Interconnect PCA 3 Thermoswitch 7 Pressure Roller 4 Heat Lamp Table 1-1Fuser Assembly Configuration 6-48 Removal and Replacement
Removing the Fuser Roller Heat Lamp 1Laser Jet 4 only: Remove the (2) latches that hold the right side cover. (There is a gear exposed on the right side of the fuser, see Figure 6-41, callout 1 .) 2Release the (7) latches on the LaserJet 4 or the (5) latches on the LaserJet 4 Plus that hold the wire cover to the Fuser Assembly. These latches can be accessed through slots on top of the fuser. (continued on next page) Figure 1-41 Fuser End Cap Removal (LaserJet 4 only) 6-49 Removal and Replacement
3LaserJet 4: With a screwdriver, release the latches by first pressing to clear the lower latch, then lifting to release the upper latch (see Figure 6-42a). LaserJet 4 Plus : With a screwdriver, release the latches by first pressing to clear the lower latch, then lifting to release the upper latch. Repeat until all (4) latches are free, then rotate the cover to release the latch on the side (see Figure 6-42b and 6-42c). 4Release the two end latches (see Figure 6-42b). Note Six of the seven latches are accessed from the top of the wire cover. These latches are beneath the felt pad. The slot on the front left side of the wire harness cover is the best place to begin removing the cover. Figure 1-42 Fuser Wire Harness Cover Removal (LaserJet 4) 6-50 Removal and Replacement
(continued on next page) Figure 1-42b Fuser Cover End Latches (LaserJet 4 Plus) Figure 1-42c Fuser Wire Harness Cover Removal (LaserJet 4Plus) 6-51 Removal and Replacement
5Remove the (1) Heat Lamp lead (thermoswitch screw)(see Figure 6-43 callout 1). 6Press the thermoswitch tab towards the paper exit flag to release the tab (see Figure 6-43 callout 2). Slide the Thermoswitch off the fuser frame (see Figure 6-43, callout 3). 7LaserJet 4 : Remove the cable retainer from the fuser frame, and free the heat lamp lead from the cable retainer. Note the orientation of the cable retainer. LaserJet 4 Plus/5: Remove the (2) screws from the end cover (see Figure 6-43, callouts 4 and 5). Note the wavy washer on the (1) screw touching the copper contact (see Figure 6-43, callout 4). Remove the thermistor connector from the frame and pull apart (see Figure 6-43, callout 6). Note the position of the Fuser Shipping Lever and remove from assembly. (continued on next page) Figure 1-43 Left Side Fuser Cover 6-52 Removal and Replacement
NoteLaserJet 4 and 5 only: Note the orientation of the bushing on the left side of the Fusing Roller. 8Squeeze the lamp connector to release the slip-on connector locking tab from the right side of the heat lamp (see Figure 6-44, callout 1). (continued on next page) Figure 1-44 Gear Side Heat Lamp Connector 6-53 Removal and Replacement
NoteBefore removing the gear cover, note the routing of the wires in the gear cover slots. 9Remove the (2) screws from the right side gear cover (see Figure 6-45, callouts 1 and 2). Note the wavy washer on the (1) screw (callout 1) touching the copper contact. Remove the cover. 10Remove the Heat Lamp (see Figure 6-45, callout 3), from the roller. Pull the lamp out the side of the assembly. Figure 1-45 Fuser Gear Cap Removal 6-54 Removal and Replacement
Fuser Assembly Thermoswitch Removal NoteSix of the seven latches are accessed from the top of the wire cover. These latches are beneath the felt pad. The slot on the front left side of the wire harness cover is the best place to begin removing the cover. 1Remove the Wire Harness Cover as shown in Figure 6-42a (LaserJet 4) or Figure 6-42b and c (LaserJet 4 Plus). 2Remove the (2) screws from the Thermoswitch connector (see Figure 6-46, callout 1). 3Release the thermoswitch latch from the paper sensor flag side of the Fuser Assembly (behind the side cover). (See Figure 6-46, callout 2). 4Slide the Thermoswitch to the gear side of the fuser and release it from the fuser frame (callout 3). Figure 1-46 Fuser Thermoswitch Connectors 6-55 Removal and Replacement
Thermistor Removal 1Remove the Wire Harness Cover as shown in Figure 6-47. 2Remove the (2) screws from the thermoswitch connector (see Figure 6-47, callout 1). 3Release the thermoswitch latch from the paper sensor flag side of the Fuser Assembly (behind the side cover, see Figure 6-47, callout 2). 4Slide the thermoswitch to the gear side of the fuser and release it from the fuser frame (callout 3). Note When installing the thermoswitch, make sure the sensing surface contacts the fusing roller uniformly. If it does not, straighten the leaf spring. (continued on next page) Figure 1-47 Thermistor Connector 6-56 Removal and Replacement