On Sun, 6 Jan 2008 04:24:08 -0800, "William Sommerwerck"
wrote:

My LaserJet 4M has suddenly developed a serious problem -- just as I need it
to get out some important documents.

It's printing black lines across the width of the paper, about 1/8" to 1/4"
wide. They occur randomly (two to three per page) and look as if someone has
run a Magic Marker across the document.



If the lines are horizontal when looking at a portrait page, then it's
probably not the toner cartridge. It could be the laser, or HV
supply, or any number of other things. I would get another laserjet 4
and do some parts swapping. These printers are so cheap and easy to
find that it's not worth spending a lot of time on, or buying a
service manual. The toner cartridge is the most common problem. If
you get another with a bad toner cartridge (vertical lines is the most
common failure), then you can fix it with your good toner cartridge.

If you get a regular 4, you can swap the postscript SIMM into it to
turn it into a 4M. Don't get a 4+ because they are different and
won't work with the 4M's SIMM.
Andy Cuffe