I have a brother HL-L2320D printer, and I was working on a circuit board mask with Eagle PCB.
In the program options I chose to print a solid black PCB artwork. When I use a regular blank sheet of 8.5x11 inch paper in the automatic front feeder, the printout appears fine except a few spots were white when they should be black.
I then rocked the toner cartridge a few times and cleaned the drum unit as per operating instructions. I tried again with another sheet of regular paper but the sheet felt like it was somewhat damp, but not damp enough to crinkle. Anyway, with that somewhat damp paper as my only test paper at the time, I then used it and the printout came out as expected.
Now I proceed to use a sheet of staples transparency and I removed the white tab off of it before putting it into the printer. I put the coating side up so that the toner goes on the smooth side. Once I printed it out, the design came out fine, however the coloring was inconsistent. I expected a straight black image, but instead of straight black, it seems that the black portions are replaced with a darker shade of the same design shifted down the page. It's as if the printer was trying to print the same thing twice in two different formats.
Why would a printer do this when I configured my software and printer to make the output only black? I tried to use the thin paper setting and the thick paper setting for the transparencies and the results actually were worse (and the printer took longer to print the page) on the thick paper setting.
What can I do to fix this?