DIAGNOSIS A repeating defect indicates a problem with a rotating component. A vertical line is typically caused by a scratch or toner buildup on the drum unit's green surface.
FIX Remove the drum unit. Locate the green photosensitive drum cylinder. Gently rotate it by hand and look for a thin scratch or a line of adhered toner. Wipe the entire drum surface lengthwise with a dry, lint-free cloth to remove any debris.
IF THAT DIDN'T WORK If the line remains in the exact same position after cleaning, the drum is physically scratched and must be replaced (DR-2350). Do not attempt to repair a scratched drum.
HEADS UP Never touch the green drum with fingers; oils cause permanent print defects. Never clean the drum with alcohol or solvents; use only a dry cloth.