Repetitive Defects Rulers - Black and White HP LaserJets

Repetitive defect rulers help determine what component  is causing the repetitive image defect. You simply measure the distance  between defects and look up the corresponding component. That said, you  really don’t need these rulers. Repetitive defects are almost always  caused by the toner cartridge or fusing assembly, and occasionally the  transfer roller. If you have an extra toner cartridge or fusing  assembly, swap them to see if the problem goes away. Otherwise you can  do a half-way test.

A half-way test is a simple test to  determine where the print defect is occurring in the printer. As paper  travels through the printer, it first passes under the toner cartridge  and then into the fusing assembly. Color printers are a bit more complex  but the concept remains the same. The idea is to interrupt printing  before the paper gets in the fuser. What you do is print a page and open  the toner lid when you think the paper is underneath the toner  cartridge. This will stop printing and you can pull the toner cartridge  out and look at the partially printed paper. It may take a few tries to  time it so the paper stops under the toner but not completely into the  fuser. If the repetitive print defect is on the page before the paper  reaches the fuser, then the fuser is not the problem. It’s probably your  toner cartridge or maybe the transfer roller.

Another simple check is to remove the  fuser and look at the long rollers in the fuser. If you see toner baked  on the rollers or any other gunk then you need to replace the fuser.  Fusers with plastic fixing films, also called sleeves, can tear. This  usually causes a smear of toner all the way down the page where the  sleeve is ripped.