For a while now my HP2600n color laser printer has been having problems with printing magenta. The left side just faded away to almost nothing. I assumed it was the toner cartridge and I finally got around to replacing it yesterday. Unfortunately the new toner did not fix the problem.
InterWeb to the rescue. I did a search for magenta and 2600n and came up with this hit: http://www.fixya.com/support/t3541632-red_colour_fades_both_left_right_sides. This led me to a PDF that describes in detail how to take apart the printer to get access to the laser module where I was able to clean two of the mirrors that direct the laser to the toner cartridge drums. The mirror for the magenta toner was very dirty and I am surprised I was able to get anything out of it. the yellow toner mirror was also dirty but no where near as bad as the magenta mirror. I cleaned the mirrors and put the printer back together only forgetting to put two cables back on. Fortunately I noticed after putting in only nine of the next 11 screws. Once everything was back together I tried a test print with the new toner and it came out perfect. I then put the old toner back in and tried it as well and it also printed perfectly. Now I just have to see if I can return the new toner.