HP 1200 printing vertical line

Archived from groups: comp.periphs.printers (More info?)

I noticed a black/gray vertical line being
printed in the left side of the page.

This only happens if I print a logo or a black
box in the left part of the page then below a
black line appears then starts fading after 2
or 3 pages that don´t use that amount of black
color in that left area.

I tried a new toner and same problem, I don´t
know much of printers, but there is a small roller
in the printer, I don´t know if that could be the problem?

Thank you for any further information.
Printer:
HP LaserJet 1200
Always used genuine HP toners.