Canon MF728 horizontal lines/ streaks on both black and color prints

[Mister C]

Hello there!
I'm dealing with a printer which prints out thick horizontal lines at random places on the page, but mostly at the same distance between each other.
When printing B/W only, there are only black lines and when printing full colour, lines from each colour are also printed. The lines are present both on copy and normal print.

I've done the following:
- updated the firmware.
- opened up the printer and cleaned everything.
- opened up the laser and cleaned the polygon mirror as it was dusty.
- replaced toner with PC drum units.
- replaced transfer belt.

Unfortunately, the printer is operating with 3rd party toners and no Canon OEM parts are desired by the end user. Because of this the printer doesn't let me run its calibrations.

Any idea if the issues come because of the 3rd party toners or is there an underlying issue with the device itself or other components?

[Tom]

Did you ever figure this out? I have an MF726 which is basically the same machine acting very similar with those horizontal lines. Doesn't matter if it's copy/print or an internal report. It's a pretty thick defined line about 2/3 an inch thick, usually 3 per page but it varies. I see some faded color lines of the same thickness somewhat overlapping the black even when just printing black and white, but that's intermittent. Not a high value machine worth spending a lot of time or swapping expensive parts on, but I'm still curious if it's something simple like a poor ground or something, or is it sensor or DC controller?

[Drivee]

Hi,
First, the vertical lines coming from Cyan cartridge. Need to be replaced. Regarding horizontal lines, this is know problem. Please reinstall cartridges, turn printer on, make calibration. It will work.