HP 8550mfp Service Manual - Page 158

Transfer kit life detection The transfer kit life is determined by both the page and image counts. The number of images printed is stored in the formatter, and the controller board senses the transfer kit life expiration based upon this data. When the life data reaches 149,000 pages or 299,000 images total, TRANSFER KIT LOW / REPLACE KIT is displayed on the printer control panel. The printer is still able to print after the transfer kit low warning. The formatter counts the number of printed images after the transfer kit low warning occurs. When the number reaches 150,000 pages or 300,000 images, the controller board signals TRANSFER KIT OUT / REPLACE KIT. End of life behavior is determined by the TONER LOW setting on the printer control panel (see page 88). Printing can continue after the transfer kit out signal; however, print quality might be degraded and the number of jams might increase. Because there is not a memory mechanism in the transfer devices, users and service personnel must reset the transfer count when a new transfer kit is installed. Also, if the formatter board is replaced, the transfer count must be reset in the Service menu. Fuser kit life detection The controller board senses the fuser kit life expiration based upon page count stored in the formatter. When the page count reaches 99,000 pages, FUSER LIFE LOW / REPLACE KIT is shown on the printer control panel. The printer is still able to print after the fuser kit life expiration warning. The formatter counts the number of printed images after notification occurs. When the number reaches the 100,000 pages, the controller board signals FUSER LIFE OUT / REPLACE KIT. End of life behavior is determined by the TONER LOW setting on the printer control panel (see page 88). Printing can continue after the fuser life out signal, but print quality might be degraded. Color toner level detection The color toner level sensor (PS621) detects the toner level in the color toner cartridge. PS621 consists of a light emitter and a light receiver. The light from the light emitter enters the detection window at the light guide facing the outside of the toner cartridge. The light entering the detection window passes through the inside of the cartridge. Then the light guide at the stirring plate cleans the toner 156 Chapter 5 - Theory of operation EN