Horizontal lines on every page LaserJet

[baberb]

I’ve got a LaserJet M608 that required replacement of the Paper Pickup Assembly. I got it put back together and the original issue is fixed, however now it is having print quality issues, there are horizontal lines going all the way across the page now, in the same spot on every page. 

Actually the first page of any batch has a thick black bar towards the leading edge of the page that comes out of the printer first. Only the first page, none of the other pages have this smudge, and it is consistently on the first page of every print job. 

then there is a black smudge a few inches above that, and it’s repeated in the same spot on every page. 

Of course we swapped the toner cartridge with an identical printer next to it, and the problem stayed with the printer, it does this with any toner cartridge.  We tried the same thing with the fuser. 

What could be causing this? Are there any troubleshooting steps I can do to identify the cause?

[Repairatrooper]

If the defects are evenly spaced you can measure the gap and then check a repetitive defect ruler to see what the spacing lines up with.