Brother International HL-2600CN Service Manual - Page 86

(2) Laser Drive Control Circuit Laser Drive Control Circuit (LDC) consists of the video signal input circuit, laser drive circuit, laser diode, output sensing circuit and output control circuit, as shown in Fig.4-34. (1) When the video signal is received, the laser drive control circuit switches the laser diode according to the video signal data. (2) The radiated laser beam is sensed by the photo detector (PD) and the signal is fed back to the output control circuit. (3) The output control circuit controls the laser output to make the level constant by comparing the laser output with the feed-back value transmitted from the output sensing circuit. (4) The scanning laser beam is sensed by the beam detector (PD), then the beam detecting timing (BDT) signal is output. MCTL PWB 2 PRINT Signal Frequency Control Circuit OPC Belt F- Lens VIDEO Signal Beam Scanning Control Circuit Synchronizie Control Circuit BDT LCD PCB Laser Scanner Motor Fig.4-34 IV-35