HP 4550 Service Manual - Page 234

Table 7-3 Numerical printer error messages (continued) 50.7 FUSER ERROR 3. Referring to Figure 7-36, measure the resistance for both the upper and lower thermistors. The resistance should be between 430K ohms and 310K ohms at room temperature (25° C, 77° F). If the resistance exceeds limits, replace the fusing assembly. If resistance is within limits proceed to step 4. 4. Verify the connectors at J1011 of the DC controller PCB and J1 of the DC power supply assembly are firmly seated. 5. Replace the power supply assembly. Description: Action: The fusing motor (M1) drives the fusing assembly, 1. the paper transport (web) assembly, ITB lift mechanism, transfer roller, transfer roller lift mechanism, and the face down output delivery drive 2. assembly. A 50.7 fuser error appears when PS6 detects no motion within the fuser. Photosensor PS6 Power cycle the printer to try to clear the message. Remove the left-side cover of the printer. Verify that the fusing motor (M1) connector is seated firmly into J102 of the feed PCB. is the fusing unit pressure switch shown in Figure 7-27. 3. Ensure that the connector at J110 of the feed PCB is firmly seated (this connector contains the wiring for PS6, which provides fuser-motion feedback). 51 LASER ERROR (4500) -or- 51.X PRINTER ERROR (4550) Description: Indicates a beam detect error or laser failure. Note Closely inspect the mechanical linkage. The gears along the gear "drive" path can bind the gears, which will prevent M1 from rotating. 4. If the error persists, Observe the drive shaft of M1 (refer to Figure 7-31) while powering on the printer. If this shaft DOES NOT rotate, your failure is related to the motor drive circuitry. Referring to the printer's wiring diagram, verify that connectors J102 and J106 of the feed PCB are firmly seated. If the error still persists, replace the fusing motor and the feed PCB in sequence. 5. If the shaft rotates (both forward and reverse), and the 50.7 fuser error appears, the cause of the error is related to the motion feedback circuitry. Remove the fusing assembly and verify the sensor flag (see Figure 7-27) is in good condition and functional. Verify the connector at sensor PS6 (see Figure 7-27) is firmly seated. Clean the sensor of dust and debris. If the error persists replace sensor PS6. Action: 1. Turn the printer off and on to reset the printer. 2. Verify connectors J1102 on the laser driver PCB and J1008 on the DC controller are seated properly. 3. Verify connectors J551 on the beam detect PCB and J1006 on the DC controller are seated properly. 4. Replace the laser/scanner unit. 232 Troubleshooting C7085-90921