HP 4300 Service Manual - Page 88

Control system overview The control system consists of the power supply and the DC controller PCA. It controls the pickup and feed, laser/scanner, and image formation systems. The microprocessor on the DC controller PCA controls the operating sequence of the printer. When the printer power is in the standby sequence (see table 30 on page 67), direct current power (dc voltage) is supplied to the DC controller PCA by the power supply. When the printer is in the standby sequence (see table 30 on page 67) the microprocessor on the DC controller PCA sends signals to turn on and off various solenoids, motors, and other printer components needed to process and print the image data input by the host computer. Pickup and feed system overview The pickup and feed system consists of a motor, various rollers, and sensors that detect the presence of media, transport the media into and through the printer, and deliver the media to an output bin. If during the transport process, the media does not reach specific sensors in a specified time, the microprocessor on the DC controller PCA halts the motor and a jam message appears on the control-panel display. Laser/scanner system overview The laser/scanner system forms a latent (or potential) image on a photosensitive drum according to signals sent from the microprocessor on the DC controller PCA. The main components of the laser/scanner assembly are the laser driver PCA, the scanner motor and a six-sided mirror. The DC controller PCA sends image data signals to the laser/ scanner assembly. The laser/scanner PCA converts these data signals into a laser beam of light. The laser beam of light is reflected by the six-sided mirror onto a photosensitive drum (in the print cartridge) and a latent image of the image to be printed is created. Image formation system overview The image formation system uses toner in the print cartridge to transfer the latent image on the the photosensitive drum to the media. Heat and pressure (from the fuser) are used to permanently bond the toner image to the media. The photosensitive drum (in the print cartridge) receives a uniform negative primary charge that will be exposed to the laser beam of light. The photosensitive drum is exposed to the laser beam and an electrostatic latent image is created on the drum (this image is invisible to your eye) by the laser neutralizing specific areas of the drum's surface. When the areas exposed to the laser beam come in contact with toner, the toner is attracted to them (now the image can be seen on the drum). The transfer roller applies a positive charge to the back of the media. As the media passes the photosensitive drum the toner image is attracted to the media and transfers from the drum to the media. The media then passes through the fuser where heat and pressure are applied to permanently bond the toner to the media. 68 Theory of operation Q2431-90912