The inside of your laser printer contains a device called a drum; when the drum starts to go bad, the quality of the printouts will suffer. But since a number of other faulty parts can cause a deterioration in print quality, it is important to properly diagnose the problem and make sure that it is the drum that is causing it.
Blurry images and missing text are both classic signs of a failing toner drum. When the drum begins to wear out, it is no longer able to transfer the images to the paper properly, and when this happens, part of the text can become blurry and unclear. The drum is most likely to blame for this problem, especially if the text is missing or blurry in the same spot on every page.
The printer drum might be faulty if you notice lines that appear consistently on each of your printed pages. This is particularly true if the lines appear in the same spot consistently. The lines that indicate a failing printer drum are often faint at first, but they become darker and darker as the drum deteriorates. Keeping an eye out for those first faint lines is one of the best ways to diagnose a bad drum. This will also give you time to order a new toner drum before the old one becomes unusable.
Spots on the paper can be caused by a number of things, including a faulty or leaking toner cartridge, or a bad printer drum. The easiest way to determine whether the spots are the result of a bad toner or a bad drum is to change the toner cartridge and clean the inside of the printer. If the spots continue after the toner has been replaced, the problem is most likely the drum.