Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Replacing the drum is the obvious advice to give. I presume you have tried that?
Unless, of course, there is some other component in the printer which rotates, and is that circumference also.
Can you scan a copy of the lines on a page (preferably a photocopy of a blank original, so as to show them most clearly), and add the scanned image file to your reply, please? that would help considerably.
(Without such an aid, I have no advice at this point except to check the fuser rollers... I doubt any of them are that circumference, but if one is damaged with a horizontal line then it should show up.)
OK. Take your time, please.
I was on another case for a bit, I will now take a look. Thanks for posting it!
I note that those lines are far far too regular-looking to be anything like the usual 'drum damage' lines.
But they are associated with the drum owing to their spacing apart.
So I think you need to look for a chipped gear tooth, or something stuck in the gears that turn the drum or drive the drum... if the drum were joggled just a trifle once per revolution, it might produce that sort of line.
(I regret that I am not able to offer Live Phone Call service at this time; However, your request is still open to other Experts in this category, and one of them may pick up on it at any time.)
Another possible cause would be, if the power supply produces a spike every revolution. Then this sort of line would appear, without any visible mechanical or material cause. Replacing the power supply in the printer will cure this, though, and be the evidence that this is the case.
Later is fine. Get back to me at your convenience.