HP Color LaserJet 8500 Service Manual - Page 184

Tray 1 pick-up - One sheet of paper is pressed to the multi- purpose pick-up roller by the paper lifting plate and is picked up by the rotation of the pick-up roller. Any extra sheets are removed by the separation pad, then sent into the printer. Operation after transmission is the same as for tray pick-up except that the paper lifting plate solenoid is reset on to lower the paper lifting plate right after registration roller rotation. • Tray 1 paper-width sensor - The tray 1 paper-width sensor (PS1701) detects the paper width when the user adjusts the media width guides, which moves the slide resistance connected with the size-control plate. When paper is loaded in tray 1, the controller board detects the paper width. If the paper width is not the width specified by the formatter, the controller board notifies a paper-size failure to the formatter and stops the printer. • Tray 1 last-page detection - The tray 1 last-page sensor (PS19) monitors the rotation of the last-page detection roller in tray 1 and detects the last page. If the tray has two or more pages, the last page detection roller does not rotate at pick-up. When the last page is picked up, the last-page detection roller rotates past the page and PS19 and sends an off to signal the controller board. The controller board then signals the formatter that no pages are in tray 1 and stops the next image formation. The PS19 detects no page before the next image is written and prevents the imaging drum and the transfer drum from getting dirty. 182 Chapter 5 - Theory of operation EN