Introduction This section presents the theory of operation and the functional overview for HP Color LaserJet 4500 series and 4550 series printers. It provides the service representative with an understanding of the printing process. This chapter is also the course material for the Service Authorization class and discusses the following printing functions: Basic operation Image formation Toner density Mechanical system Paper path DC controller subsystem Motors and fans Formatter system Power supplies Toner level sensing system 102 Theory of operation C7085-90921