Open the front cover and pull out the drum unit and toner cartridge assembly.
Clean the primary corona wire inside the drum unit by gently sliding the blue tab from right to left several times.
Return the blue tab and snap it into the Home position.
If you do not return the blue tab to the Home position, your printed pages may have vertical black stripes on them.
Reinstall the drum unit and toner cartridge assembly in the machine.
Close the front cover.
If the message like "Drum Error" or "Dust on Drum" continues to appear on the LCD after cleaning the corona wire, try cleaning the metal contacts with a dry lint-free soft cloth.
I have done that and still get dirty prints as if the roller has awash with wet ink!
Remove the drum unit and toner cartridge assembly, and then remove the toner cartridge from the drum unit.
Position the print sample in front of the drum unit so you will know the exact position on the drum that is causing the poor print.
Turn the black gear on the drum as you check the surface of the OPC drum. The OPC drum is photosensitive so do not touch it with your fingers.
When you find the substance on the drum surface that matches the print sample, gently dab the surface of the OPC drum with a cotton swab that is lightly dampened with isopropyl alcohol.
If the print quality still has not improved you need to install a new drum. Click here to see the instructions to install a new drum.