When a user tries to print a document on a laser printer, vertical lines appear on the printout. Which of the following should the technician replace?

In a laser printer, the imaging drum is a photosensitive cylinder that holds an electrostatic charge to attract toner and form the image. A scratch or a defect on the surface of the drum will consistently fail to hold the charge properly during each rotation. This results in a continuous streak where toner is either incorrectly applied or repelled, creating a distinct vertical line down the entire length of the printed page. Therefore, replacing the drum is the correct solution for this specific print quality issue.

A. Mirror: A dirty or malfunctioning mirror in the laser scanner assembly would typically cause distorted, skewed, or entirely blank sections, not a clean, consistent vertical line.

B. Fuser: A faulty fuser assembly, which uses heat and pressure to bond toner, would cause issues like smudging, ghosting, or toner that easily rubs off the page.

D. Toner: While a defective toner cartridge can cause various print quality problems, the specific symptom of a sharp, repeating vertical line points directly to a physical defect on the drum's surface, not the toner supply itself.

1. Hewlett-Packard (HP) Official Documentation: In the support document "HP LaserJet Printers - Resolving Print Quality Issues

" under the section for "Vertical lines or streaks

" the primary cause listed is: "The most likely cause is a scratched photosensitive drum inside the print cartridge." (HP Customer Support

Knowledge Base

Document ID: c01491023

"Vertical lines or streaks" section).

2. Brother Industries

Ltd. Official Documentation: In a troubleshooting guide for vertical lines

Brother's support documentation states: "If the print quality has not improved [after cleaning]

the drum unit may be damaged. Install a new drum unit." This directly identifies a damaged drum as the cause of vertical lines. (Brother Solutions Center

FAQ ID: 000000004

"Vertical lines or a vertical streak appears on my printouts

" Step 4).

3. University of Wisconsin-Madison Courseware/IT Documentation: The Division of Information Technology (DoIT) KnowledgeBase article on "Laser Printer - Troubleshooting Print Quality" identifies "Lines/streaks down the page" as a common problem. The listed cause is "A scratch in the photosensitive drum

" and the recommended solution is to "Replace the toner cartridge" (as the drum is often integrated). (University of Wisconsin-Madison

DoIT KnowledgeBase

Doc ID: 7328

"Lines/streaks down the page" row).