Printer Faults -
Repeating Marks at Intervals

Marks repeating vertically down the page usually come from one of the rollers. As the rollers turn a mark on it will normally occur at regular intervals matching it's circumference down the page

Vertical repetitive defects most likely come from contamination on the print cartridge drum; the fuser is next most likely. Measure the pitch of the interval and try to match it with the rollers in the printer.

Service manuals generally have a "defects ruler"; unfortunately printer manufacturers don't seem to like making the service manual readily available - or at best they are "conflicted" on the point.

It is possible to gauge which roller is likely to be to blame by eye. Look at the print cartridge photoconductive drum - they can usually be rotated by thumb pressure on the drum in the direction it would travel when printing. - Look for marks. Likewise with the fuser. Sticky marks on the drum or fuser rollers can sometimes be removed by gentle rubbing with a cotton bud moistened with water, saliva or isopropyl alcohol. Do not rub hard on foil fusers - it will burst the foil.

Vertical marks at a very small dot-pitch - every second line or every fifth for instance could come from the optics - a scratch or contamination on the scanner mirror for instance. It is also possible to get odd patterns due to failure of drive circuits in LED heads.

Horizontal repeated marks aren't likely because nothing but the laser-scanner works that way. It is possible to get horizontal jitter in line position if the laser scanner bearing is on its way out - the polygon mirror position is slightly incorrect at each scan.

It is possible to get horizontal marks at intervals with an A3 or larger printer producing pages sideways. If the paper path in the printer is A3 and the paper is A4 then it makes sense to print the paper sideways on - the printer only has to roll through 200 mm of paper rather than nearly 300mm so it goes nearly a third faster. All the rules are as for vertical marks - it's just that the paper is turned through 90 degrees.