I am getting horizontal white lines in my prints. They are uniform and about 3.5 inches apart

[PRD-Raymond]

I am getting horizontal white lines in my prints. They are uniform and about 3.5 inches apart. On any color.

The Paper advance calibration do not fix the problem. Problem show when printing from the computer and when printing the internal demo page on the printer.

[Valsimot]

It could be a dirty spot on a encoder disk, and when the spot reaches the sensor printer printer skips a line. 

[Repairatrooper]

Do you have the same issue if you print in High Quality mode? 

[D Hook]

I had the exact same problem on a T1200 (same basic printer as your 2300) and it was indeed a dirty encoder disk.  Ended up being grease that was over-applied at the factory and had dripped down onto the disc.  I ended up replacing the disk but I think you might try cleaning yours before replacing.

If you don't have a service manual, they're readily available on the internet.  Here's a link to a PDF copy:

https://www.laserexpressinc.com/manuals/HP/hp-dsj-t790-t1300-z5400-t2300-service-manual.pdf

Check page 375 for the disc.  It's not hard to locate on the printer once you remove the left spitoon.  Let us know how it goes.