Dell E515dw User Manual page 320

5. Turn the drum unit as shown in the illustration. Make sure that the drum unit gear is on the left side.
6. Turn the edge of the drum unit toward you by hand while looking at surface of the suspected area.
NOTE: To avoid print quality problems, DO NOT touch the surface of the drum unit except the edge .
7. Wipe the surface of the drum gently with a dry cotton swab until the mark on the surface comes off.
320 Routine Maintenance