> When Images like These Are Output > Streaks Appear in Your Printouts > Streaks that are parallel to the direction of feed appear in the printout
4WK8-01U

Streaks that are parallel to the direction of feed appear in the printout

The corona assembly wires inside the main unit are dirty. Clean the wires.
← Feeding Direction
Remedy
Clean the corona assembly wires inside the main unit several times.
Press  → [Adjustment/Maintenance] → [Maintenance] → [Clean Wire].
 "Maintenance" > "Routine Cleaning" > "Output Paper Becomes Dirty (Wire Cleaning)" in the User's Guide