Sharp FO-2970M Service Manual - Page 50

FO-2970MU g. Electrical connection ASIC (LR38784A) CONTROL PWB 136 SAMP 146 VIDEO 135 SYNC134 APCSTT 133 PMD- PRINTER PWB +24V CNLSU 1 +24V 2 DG 3 VIDEO 4 SAMP 5 SYNC6 APCSTT 7 PMCLK 8 PMD- CPU (SH7041) 65 SYNC- 114 PMCLK CNPRT CN601 1 +24V 2 DG 3 VIDEO 4 SAMP 5 SYNC6 APCSTT 7 PMCLK 8 PMD- LSU PWB IC603 3 3-terminal 1 regulator 2 Laser beam detecting PWB (Start position detecting PWB) CN603 1 +5VL 2 SYNC_ 3 GND CN604 1 +5VL 2 SYNC_ 3 GND +24V CN602 1 GND 2 PMD3 +24V 4 PMCLK 5 GND Scanning motor (APC circuit) Q603 51 INH OUT LD 4 /PD GND IC601 3 IM VCC VPS 78 +5VL 4 5 VR601 CONT VDD Fig. 12 3 GND 2 IC603 O/I I/O 1 The laser diode control board is driven in synchronization with the VIDEO signal sent from the CPU board. By the operation of the laser diode control board, infrared laser beams of 780nm are outputted from the laser diode and made in parallel by the collimator lens, and focused onto the scanning motor by the first cylinder lens. The scanning mirror rotation is controlled by the scanning motor to be constant at 11811rpm (600dpi) and 8000rpm (400dpi), and the laser beam is directed to the main scanning direction. The scanning motor is of six-surface, and six-line print is made for one rotation of the scanning motor. The laser beam reflected by the scanning mirror is directed to the curved mirror by the first reflection mirror. Before reaching the curved mirror, the laser beam enters the photo sensor on the start position detector board, making vertical synchronization and print data synchronization (generating the SYNC signal). The curved mirror directs the laser beam to the second reflection mirror in parallel and in even interval regardless of difference in angles of incidence from the first reflection mirror. The laser beam reflected by the second reflection mirror ia passed through the second cylinder lens to reach the photoconductor drum. The second cylinder lens corrects blur of the images caused by variations in the installing angle due to the two-surface scanning mirror, providing stable laser beams to the photoconductor drum for each line. h. Fusing unit control The fusing section is heated by the heater lamp (400W). The heater lamp is controlled (turned on/off) to keep the optimum temperature. The following signals are outputted by the ASIC and CPU for control. 1) Signal functions • HLON This signal is to turn on/off the heater lamp. When this signal is outputted, photo triac PD101 turns on to turn on triac T2. Then an AC power is supplied to the heater lamp to turn on the heater lamp. • RTH This is the output signal of the thermistor which detects the surface temperature of the heat roller. It is inputted to the CPU. The heater lamp is turned on/off depending on the value of RTH voltage. 5 - 14