We have three HP 4000/4050 LaserJet printers that have the same problem printing. The printed page, a test page, starts off printing fine on the left side of the page then about half way across starts fading to almost unseen text. We've replaced the toners, transfer rollers, transfer guides, and even the Engine board on one printer trying figure out what is causing this problem. I thought maybe the connections to the transfer roller was causing the problem, so we replaced the Registration Assembly and still right side fading down the side of the page. We checked the scanner and tried another just to verify and still no help. We are at our end of the rope on these printers. HELP!!!