CompTIA A+ 220-1101 (V14) Practice Question

Consistent vertical lines on every page of a laser printer almost always point to a defect or contamination on the photosensitive imaging drum. A scratch or a streak of residual toner on the drum stays in the same spot for every revolution, so the flaw is reproduced as a solid line in the same position on each sheet. Inspecting, cleaning, or replacing the drum (or the combined toner-drum cartridge, depending on the model) is therefore the first step. A dirty corona wire can also create vertical stripes, but these are usually lighter or intermittent and the wire is cleaned when servicing the drum. Printer calibration addresses color alignment, and paper type problems tend to cause jams or smudging, not a sharp vertical line.