Printer problem:

I have a pretty elderly TI Microlaser Plus printer that prints a horizontal line across each page about 1/4 the way down the page.There is other print that one can also see very faintly on the page as well if one looks closely that seems to be retained in memory.The desired printout is fine with the exception of that line that shows up, and it pretty well overwrites anything else in the area of desired printing.I have cleaned until I am blue in the face, and replaced the exit rollers. I would have thought they would have caused a vertical line anyway, not horizontal.Any ideas would be appreciated.RTH