Lexmark C510 Service Manual - Page 76

5021-0XX Laser drive control circuit The laser drive control circuit (LDC) consists of a video signal input circuit, laser drive circuit, laser diode, output sensing circuit, and output control circuit. See the illustration. 1. When the video signal is received, the laser drive control circuit switches the laser diode switch on and radiates according to the video signal. 2. The radiated laser beam senses the photo detector (PD). The detected signal is returned to the output control circuit. 3. The output control circuit controls the radiated output to a constant, by comparing the laser output default with the feedback value transmitted from the output sensing circuit. 4. The laser beam, scanned by the scanner motor, is sensed by the beam detector (PD), and then outputs the beam detecting timing (BDT) signal. 1-50 Service Manual