Sharp AL-840 (serv.man3) Service Manual ▷ View online
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CCD unit
Images (light) is converted into an electrical signal (analog signal) by
the CCD.
the CCD.
The image signal read by the CCD is converted into a digital signal b
the A/D convertor in the MCU PWB and outputted to the ASIC, where
the image is processed.
the A/D convertor in the MCU PWB and outputted to the ASIC, where
the image is processed.
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Scanner motor
The scanner unit is driven by the scanner drive motor.
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Scanner home position sensor
The scanner home position sensor senses the scanner position. The
copy image position control is performed by the sensing timing of this
sensor.
copy image position control is performed by the sensing timing of this
sensor.
*
Zooming
Zooming is performed by changing the copy magnification ratio in the
sub scanning direction or changing the scanning speed.
sub scanning direction or changing the scanning speed.
The copy magnification ratio in the main scanning direction is
changed by the software in the ASIC.
changed by the software in the ASIC.
C. Scanner (writing) section
(1) Outline
In this section, the dot image data sent from the MCU PWB are
converted into laser beams (ON/OFF), which are scanned to form
latent electrostatic images on the OPC drum. It is composed of the
laser beam generating section (where dot image data signals are
converted into laser beams (ON/OFF)), the laser beam correction
section, the laser beam scanning section, and the laser beam detect-
ing section. The major parts and their functions are described in the
following.
converted into laser beams (ON/OFF), which are scanned to form
latent electrostatic images on the OPC drum. It is composed of the
laser beam generating section (where dot image data signals are
converted into laser beams (ON/OFF)), the laser beam correction
section, the laser beam scanning section, and the laser beam detect-
ing section. The major parts and their functions are described in the
following.
(2) Block diagram
(3) Major parts
VIDEO
SYNC
(PCU)
MCU
Scanning motor drive signal (PMD, PMCLK)
Laser diode
control circuit
control circuit
Laser
diode
diode
Collimator
lens
lens
No. 1
cylinder
lens
cylinder
lens
Laser beam
sensor
sensor
No. 2
reflection mirror
(curved mirror)
reflection mirror
(curved mirror)
No. 1
reflection
mirror
reflection
mirror
Motor
mirror
mirror
Drum
No. 2
cylinder
lens
cylinder
lens
No. 3
reflection
mirror
reflection
mirror
Signal
Laser beam
2)
1) SYNC
8)
7)
6)
5)
4)
3)
1 – 12
No.
Parts
Note
Code
Signal name
Name
Type
Function/operation
Active condition
1
SYNC
SYNC IN
Laser beam sensor
Bin diode
Detects the laser beam position.
By this signal the left image print
start position is controlled.
By this signal the left image print
start position is controlled.
LOW (0V) when
laser beam is
detected.
laser beam is
detected.
2
No. 1 mirror
3
No. 3 mirror
Leads the laser beam to the OPC
drum.
drum.
4
Second cylindrical
lens
lens
Corrects the laser beam
deflection by variations in the
scanning mirror angle. Corrects
the optical section dirt.
deflection by variations in the
scanning mirror angle. Corrects
the optical section dirt.
5
F
θ
mirror (No. 2
mirror)
Corrects the laser beam form and
pitch.
pitch.
6
Scanning mirror
(rotation mirror)
(rotation mirror)
Scans the laser beam and
performs imaging.
performs imaging.
7
No. 1 cylindrical
lens
lens
Adjust the direction of laser beam.
8
Laser diode
Generates laser beam. (Controls
ON/OFF for imaging)
ON/OFF for imaging)
(4) Operation
a. Wiring diagram
SYNC-
+24V
1
CN9
GND
2
VDATA
3
SAMP
4
5
APCSTT
6
PMCLK
7
PMD-
8
+24V
APCSTT
PMD-
PRSTT
CN604
+5VL
1
2
GND
3
3
1
CN603
+24V
3
1
2
CN602
PMCLK
4
5 GND
PMD-
+24V
LSU PWB
Q603
INH
OUT
VC
C
VPS
GND
IM
IC601
LD
/PD
/PD
VR601
+5VL
IC603
2
1
5
3
7
8
4
SYNC_
VSYNC
PMCLK
+24V
CONT
VD
D
GND
O/I
IC603
5
4
2
3
I/O
1
CPU
(IC5)
(IC5)
(IC8)
ASIC
LEND-
SAMP
(IC202)
ASIC
SDATA
LEND
PRSTT
VSYNC
SYNC
CN8
CN203
SYNC-
MCU(PCU) PWB
+24V
1
CN601
GND
2
VDATA
3
SAMP
4
5
APCSTT
6
PMCLK
7
PMD-
8
SYNC-
+5VL
1
2
GND
3
SYNC_
ICU PWB
Laser beam detection PWB
(start position detection PWB)
(start position detection PWB)
3-termina
regulator
regulator
Scanning motor
b. Operation
The APC circuit is started by the APCSTT signal sent from the MCU
(PCU) PWB, and laser diode is turned on/off according to the VIDEO
signal. (The laser diode is turned on when the VDATA signal is
HIGH.)
(PCU) PWB, and laser diode is turned on/off according to the VIDEO
signal. (The laser diode is turned on when the VDATA signal is
HIGH.)
When the laser diode is turned on, 780nm infrared semiconductor
laser beams are radiated from the laser diode and arranged to be
parallel beams by the collimeter lens and focused to the photocon-
ductor drum by No. 1 cylinder lens and sent to the scanning mirror.
laser beams are radiated from the laser diode and arranged to be
parallel beams by the collimeter lens and focused to the photocon-
ductor drum by No. 1 cylinder lens and sent to the scanning mirror.
Rotation of the scanning mirror is controlled by the scanning motor to
scan laser beams.
scan laser beams.
1 – 13
The scanning mirror is a 6-surface mirror. Six lines are printed for one
rotation of the scanning motor. Laser beams reflected by the scan-
ning mirror are passed to the curved mirror by the No. 1 reflection
mirror. Before reaching the curved mirror, the laser beams enter the
laser beam sensor on the start position detection PWB to make
horizontal synchronization (generating SYNC signal).
rotation of the scanning motor. Laser beams reflected by the scan-
ning mirror are passed to the curved mirror by the No. 1 reflection
mirror. Before reaching the curved mirror, the laser beams enter the
laser beam sensor on the start position detection PWB to make
horizontal synchronization (generating SYNC signal).
The laser beams from No. 1 reflection mirror are arranged to be
parallel beams by the curved mirror and passed to No. 3 reflection
mirror. The laser beams reflected by No. 3 reflection mirror are
passed through No. 2 cylinder lens to the photoconductor drum.
parallel beams by the curved mirror and passed to No. 3 reflection
mirror. The laser beams reflected by No. 3 reflection mirror are
passed through No. 2 cylinder lens to the photoconductor drum.
No. 2 cylinder lens corrects deflection of laser beams due to varia-
tions in the duplex scanning mirror installing angle, and leads the
stable laser beams for each line to the photoconductor drum.
tions in the duplex scanning mirror installing angle, and leads the
stable laser beams for each line to the photoconductor drum.
Part name
Function
Laser diode
The laser power is controlled by the
APC (Auto Power Control) circuit. In
addition, the paper empty sensor is
provided.
The laser diode radiates 780nm infrared
semiconductor laser beams under
control of the laser control PWB.
APC (Auto Power Control) circuit. In
addition, the paper empty sensor is
provided.
The laser diode radiates 780nm infrared
semiconductor laser beams under
control of the laser control PWB.
Collimator lens
The collimator lens arranges laser
beams radiated from the laser diode to
be parallel beams and converges them
on the photoconductor drum.
beams radiated from the laser diode to
be parallel beams and converges them
on the photoconductor drum.
No. 1 cylindrical lens
Adjusts the direction of the laser beams.
Scanning motor/
Scanning mirror
Scanning mirror
Used to rotate the scanning mirror.
Started by the drive signal (PMD_) from
the PCU. The RPM is controlled by the
clock signal (PMCLK_). The motor RPM
is 11811 RPM.
Started by the drive signal (PMD_) from
the PCU. The RPM is controlled by the
clock signal (PMCLK_). The motor RPM
is 11811 RPM.
The scanning mirror is a6-surface
mirror, and it reflects laser beams. By
this operation, 6 lines of printing is made
for one rotation of the scanning motor.
mirror, and it reflects laser beams. By
this operation, 6 lines of printing is made
for one rotation of the scanning motor.
No. 1 mirror
This mirror reflects laser beams to the
curved mirror.
curved mirror.
Laser beam sensor
PWB (Start position
detection PWB)
PWB (Start position
detection PWB)
Used to detect laser beams to make
horizontal synchronization.
The photo sensor on the PWB detects
laser beams to generate SYNC signal.
horizontal synchronization.
The photo sensor on the PWB detects
laser beams to generate SYNC signal.
No. 2 mirror (Curved
mirror)
mirror)
Laser beams are scanned by the
scanning mirror. But the dot interval of
laser beams radiated onto the
photoconductor differs at the center and
at the corners. This mirror corrects this
difference to provide even dot interval of
laser beams. For this reason, it is of
curved structure.
scanning mirror. But the dot interval of
laser beams radiated onto the
photoconductor differs at the center and
at the corners. This mirror corrects this
difference to provide even dot interval of
laser beams. For this reason, it is of
curved structure.
No. 3 mirror
This mirror passes the laser beams
reflected from the curved mirror to the
photoconductor mirror.
reflected from the curved mirror to the
photoconductor mirror.
No. 2 cylindrical lens
This lens is used to correct laser beam
deflection due to variations in the
scanning mirror angle.
deflection due to variations in the
scanning mirror angle.
D. Image process section
(1) Outline
This section is composed of the photoconductor section, the develop-
ing section, the transfer/separation section. Images formed by laser
beams formed by the scanner (Writing) section are converted into a
latent electrostatic images, which are formed into visible images by
toner development. The toner images are transferred onto paper.
ing section, the transfer/separation section. Images formed by laser
beams formed by the scanner (Writing) section are converted into a
latent electrostatic images, which are formed into visible images by
toner development. The toner images are transferred onto paper.
1 – 14
(2) Image forming process diagram
The operation of this section are composed of the six processes:
charging, exposure, development, transfer, separation, and discharg-
ing. An OPC drum is used as the photocoductor drum. Toner is of
one-component. For charging, the rotation brush is used. For trans-
fer, the roller is used and virtually no generation of ozone. It is also
compact. The high voltage required in this section is provided by the
high voltage power PWB.
charging, exposure, development, transfer, separation, and discharg-
ing. An OPC drum is used as the photocoductor drum. Toner is of
one-component. For charging, the rotation brush is used. For trans-
fer, the roller is used and virtually no generation of ozone. It is also
compact. The high voltage required in this section is provided by the
high voltage power PWB.
High voltage
circuit
circuit
Main charger
brush
brush
Cleaning, charging
High voltage
circuit
circuit
Discharging
brush
brush
Discharging
Paper exit
Fusing
Separation
Separation
electrode
electrode
Heat roller,
pressure roller
pressure roller
Heater lamp
Scanning
mirror
mirror
Lens
Laser diode
No. 1 -
No. 3 mirror
Exposure
Development,
residual toner
collection
Toner
Development
roller
roller
High voltage
circuit
circuit
Transfer
Paper feed roller
Paper tray
Paper
Transfer charger roller
High voltage circuit
1 – 15
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