HP 4550 Service Manual - Page 257

Banding - vertical
The doctor blade on the developer can develop notches over time. If you observe severe notching, replace the developer.
As the imaging drum gets older, the charge roller doesn't charge the imaging drum as well as it used to. If you notice buildup or contamination on the charge roller, replace the imaging drum. Black lines
The toner cartridge is defective.
The toner cartridge is not seated properly.
The fusing assembly is contaminated or damaged.
The static eliminator teeth are contaminated or defective.
The imaging drum is damaged or the waste toner collection in the drum is full. Replace the imaging drum. Black or partially black pages
Check for poor contact between the drum cartridge contact (for primary charging bias) and the primary charging bias contact. To improve the contact, clean the contacts. If the problem persists after cleaning or the contacts are deformed or damaged, replace them. If the contacts have slipped off, adjust them correctly.
Check the drum cartridge (primary charging roller). If defective, replace the drum cartridge.
Check for poor contacts in the connectors. Reconnect the DC controller PCB connector and the high-voltage PCB 2 connector correctly.
Check for a defective high-voltage PCB (primary charging bias output shortage). If defective, replace the high-voltage PCB 2.
Check for a defective DC controller PCB. If defective, replace the DC controller PCB.
If ITB clutch was removed, check for proper timing.
The black toner cartridge is empty.
Make sure clutch CL2 is connected (plugged into the paper PCA).
This defect can be caused by improper timing on the ITB clutch gears. Make sure that the cams are in sync. The two white gears on the left side of the printer (see Figure 6-47) should have two timing marks pointing toward each other. • Cams with a single line should be off one tooth clockwise on the right gear. • Cams with a double line should be aligned. C7085-90921 Chapter 7 Troubleshooting 255