I have a Hp Laserjet 3030 all-in-one and it just started printing almost solid grey over the whole page. I tried changing resolutions and other settings, ran the printer's own cleaning cycle a couple times, nothing changed. Even on draft mode it still covers the page. It's not perfectly solid, more like horizontal banding but it covers about 85% of the page or more in grey.
Since the HP 12a drums have no functions for physical cleaning, I replaced the drum entirely, put in a brand new HP 12a. Made a test print, and it has the SAME problem but now WORSE than before! The coverage is thicker and the toner darker across the page with more visible banding.
HP tech support would be my first place to look .but i have seen it before and i think is is caused by something inside that is dirty ,what happens is the tower dust kind of spills onto parts inside where the paper slides out ,i see it at work with the photo copier towner
if it was just something that was "dirty" then eventually it would stop smearing on the paper, but it's not, it prints very consitently the same way, which tells me something may be wrong with the mechanics oftransferring toner to paper. Maybe to do with the corona wire or cleaning blade or some magnetic issue.
It is also an issue inside the printer, not the toner cartridge, since I replaced that and the problem was even worse than before!
I'll keep troubleshooting, maybe I can take the think apart.