Black vertical narrow stripes when printing with a laser printer.
We make a diagnosis by the page print. What’s wrong here? What is the reason for this defect?
If the printer prints with these streaks, it indicates that the drum unit is worn out. Such a defect may appear after three or more refills of the cartridge.
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This defect occurs on all laser cartridges.
To fix it, replace the imaging drum in the cartridge.