Sharp FO-2970M Service Manual page 50

FO-2970MU
g. Electrical connection
CONTROL PWB
ASIC
(LR38784A)
136 SAMP
146 VIDEO
135 SYNC-
134 APCSTT
133 PMD-
CPU
SYNC-
65
(SH7041)
114 PMCLK
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 cylin-
der 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 scan-
ning mirror is directed to the curved mirror by the first reflection mirror.
Before reaching the curved mirror, the laser beam enters the photo sen-
sor 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 inci-
dence 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 varia-
tions in the installing angle due to the two-surface scanning mirror, pro-
viding stable laser beams to the photoconductor drum for each line.
PRINTER PWB
+24V
CNLSU
1 +24V
DG
2
3
VIDEO
4
SAMP
5
SYNC-
6
APCSTT
7
PMCLK
8 PMD-
CNPRT
LSU PWB
IC603
CN601
3
3-terminal
1 +24V
regulator
DG
2
2
3
VIDEO
4
SAMP
5
SYNC-
6
APCSTT
+24V
7
PMCLK
8 PMD-
Q603
(APC circuit)
5 1
4
GND
IC601
IM
7 8
+5VL
4 5
3
GND O/I
IC603
I/O
1
Fig. 12
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
Laser beam detecting PWB
(Start position detecting PWB)
CN603 CN604
1
1 +5VL 1 +5VL
2 2
SYNC_ SYNC_
3 GND 3 GND
CN602
1 GND Scanning motor
2 PMD-
3 +24V
4
PMCLK
5 GND
LD
/PD
3
VR601
2