What's actually going on
A thin dark line down every copy in the same place is almost always dirt or correction fluid on the narrow document glass strip used by the feeder, not a fault in the machine.
Repeating marks at a fixed interval down the page point to the drum, the charge roller or the fuser, and the interval identifies which one.
Washed-out banding across the page usually means low toner, a failing developer unit or humidity in the paper.
What to do in the next 48 hours
- 1Run the same original from the glass instead of the feeder. If the streak disappears, clean the thin glass strip left of the main platen with glass cleaner and a lint-free cloth.
- 2Print the machine's internal test or demo page. If it is clean, the fault is in the scanner path, not the print engine.
- 3Try a fresh ream from a sealed pack. Paper that has sat in a damp store room causes banding that looks like a hardware fault.
- 4If a repeating defect survives all of that, note the spacing between marks and raise a service call with that measurement.
The honest tradeoffs
- Cleaning and paper changes solve a genuine majority of streaking calls at no cost, and are worth ten minutes before you book a visit.
- Continuing to print through a drum defect wastes toner and paper and does not damage anything, so there is no urgency beyond output quality.
Your next step
Questions people ask next
- Why is there a black line on every copy from my copier?
- Nearly always dirt, toner or correction fluid on the narrow strip of glass the document feeder scans through. Copy the same page from the main glass instead: if the line disappears, clean that strip with glass cleaner and a lint-free cloth.
- What causes repeating marks down a printed page?
- A defect on a rotating component. The distance between marks matches the circumference of the part — a short interval points to a charge or developer roller, a longer one to the drum, and the longest to the fuser.
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