AR-M550 (serv.man12). (6b) Laser scan unit, Image process section, Scanner section, Fusing section, SPF section — Sharp Copying Equipment Service Manual (repair manual)

Model
AR-M550 (serv.man12)
Pages
71
Size
13.91 MB
Type
PDF
Document
Service Manual
Brand
Device
Copying Equipment / (6b) Laser scan unit, Image process section, Scanner section, Fusing section, SPF section
File
ar-m550-sm12.pdf
Date

View Sharp AR-M550 (serv.man12) Service Manual online

AR-M550/M620  DETAILS OF EACH SECTION  6 - 60
3. Laser scan unit (LSU)
A. General
This section performs the following operations. 
Image data sent from the MFP (image process circuit) through the
mother board and PCU are converted into laser beams to radiate onto
the drum surface.
B. Major parts and signal functions
Code
Signal 
name
Name
 Type
Function/Operation
MODEL
NOTE
PGM
PGM
Polygon mirror (motor)
Reflects laser beams at the constant rotation speed.
BD
BD PWB
Detects the laser scan start timing. This device is 
used to detect a laser trouble.
No.
Name
Function
1
Laser control PWB
Controls laser beam flashing and the output value.
2
Cylindrical lens
Converges laser beams to focus.
3
Incidence reflection mirror
Assures the optical path for laser beams.
4
No. 1 mirror
Assures the optical path for laser beams.
5
f
θ
 lens 1
Deflects laser beams so that the laser scan speeds on the both ends of the drum and that at the center 
of the drum are the same.
6
f
θ
 lens 2
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
12
11
10
12
11
10
9
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
12
11
10
12
11
10
13
14
15
16
17
18
13
14
15
16
17
18
4
3
2
1
6
5
4
3
2
1
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
BD
PGM
GND2
GND2
+5VLD
GND2
/PMCLK
/READY
/START
+24V1
+24V1
GND2
GND2
VRB
GND2
GND2
GND2
GND2
GND2
GND2
GND2
/LDON
LSU S/H
/SYNC
+5V2
+5V2
CN-22
B30B-PHDSS-B
VIDEO
/VIDEO
GND2
GND2
GND2
GND2
GND2
/LDON
LSU S/H
/SYNC
/VIDEO
VIDEO
GND2
SMP-18V-NC/SMR-18V-N
GND2
GND2
+5VLD
GND2
/PMCLK
/READY
/START
+24V1
+24V1
GND2
GND2
VRB
GND2
+5V2
+5V2
LD PWB
GND2
/SYNC
GND2
/PMCLK
/START
GND2
+24V1
/READY
B6B-PH-K-S
B30B-PHDSS-B
GND2
GND2
+5VLD
GND2
/PMCLK
/READY
/START
+24V1
+24V1
GND2
GND2
VRB
GND2
GND2
GND2
GND2
GND2
GND2
GND2
/LDON
/VIDEO
VIDEO
LSU S/H
/SYNC
+5V2
+5V2
+5V2
LSU UNIT
SMP-12V-NC/SMR-12V-N
TEST
TEST
TEST
(NC)
(NC)
TEST2
TEST3
TEST2
TEST3
TEST3
TEST2
/BRAKE
/BRAKE
CN-2
B4B-PH-K-S
PCU PWB
CN-1
CN-3
CN-6
CN-6
CN-8
CN-8
MOTHER
 PWB
MFP 
CONTROL
PWB
1
2
3
4
5
6
8
9
10
7
AR-M550/M620  DETAILS OF EACH SECTION  6 - 61
C. Operational descriptions
[Laser optical path]
This unit must not be disassembled in the market.
(1) Polygon mirror motor
The number of mirror surfaces and the motor RPM are reduced to
reduce noises and increase reliability.
(2) Outline of LSU specifications
7
BD PWB
Detects the timing of laser scan start. This device is used to detect a laser trouble. 
8
No. 2 mirror
Converges laser beams to focus. 
9
Plane lens
Assures the optical path for laser beams.
10
Convergence lens for BD
Converges laser beams onto the BD PWB.
No.
Name
Code, signal name
Function
RW
Control signal 
+5VLD
5V power for laser diode
RW
Control signal
/READY
Polygon mirror motor READY signal ("L" in the constant speed rotation)
RW
Control signal 
/PMCLK
Clock signal for driving the polygon mirror motor
RW
Control signal
/START
Polygon mirror motor drive start signal
RW
Control signal 
/VIDEO
VIDEO (Image signal)
RW
Control signal
/SYNC
Sync signal (SYNC) from BD, sync signal for 1 line
No.
Name
Function
Model
Number of 
mirror surfaces
Rotation 
speed
Bearing
Remark
55PPM
14 surfaces
34000rpm
AIR
Superior in silence
62PPM
14 surfaces
34000rpm
AIR
Effective scan width:
297mm
Resolution:
600dpi
Beam diameter:
Main scan = 60 -  85 
µ
m
Sub scan = 75 - 110 
µ
m
Laser power:
0.385±0.04mW
LD wave length:
770 - 795nm
AR-M550/M620  DETAILS OF EACH SECTION  6 - 62
D. Maintenance and parts replacement
(1) Maintenance and parts replacement
(List of Replacement Parts)
a. Process cooling fan unit
1) Pull out the multi paper feed tray, and remove the manual paper
feed cover F.
2) Pushing the lower part, remove the right cabinet center.
3) Disconnect the connector, and remove the process cooling fan
unit.
a-1. Machine temperature sensor
1) Remove the right cabinet middle. (See “a. Process cooling fan unit”
in this section)
2) Disconnect the connector, release the pawl, and remove the
machine temperature sensor.
a-2. Process cooling fan motor 1 (LSU, process section)
a-3. Process cooling fan motor 2 (LSU, process section)
a-4. Process cooling fan motor 3 (LSU, process section)
1) Remove the process cooling fan unit. (See “a. Process cooling fan
unit” in this section)
2) Disconnect the connector, and remove the process cooling fan
motors 1(A), 2(B), and 3(C).
b. LSU
1) Remove the process cooling fan unit. (See “a. Process cooling fan
unit” in this section)
2) Disconnect the connectors to remove the LSU unit.
No.
Unit
Parts
a
Process cooling fan unit
1
Machine temperature sensor
2
Process cooling fan motor 1 
(LSU, process section)
3
Process cooling fan motor 2 
(LSU, process section)
4
Process cooling fan motor 3 
(LSU, process section)
b
LSU
a-1
a-2
b
a
a-3
a-4
A
B
C
AR-M550/M620  DETAILS OF EACH SECTION  6 - 63
4. Image process section
A. General
Toner is attached to electrostatic latent images formed by the laser
beams which were radiated to the OPC drum charged by the main
charger, forming toner images. 
The toner images formed on the OPC drum are transferred to paper by
the transfer belt.
Composition and Applied Voltage of the Process Section
1
2
5
3
4
No.
Name
Operation
1
Toner hopper unit, toner bottle unit
Provides toner to the developing unit, and collects waste toner in the front section of the toner 
bottle unit (waste toner box section). 
2
Developer unit
Mixes toner and carrier, and attaches toner to electrostatic latent images to form visible images.  
3
Process drum unit
Forms images (electrostatic latent images, visible images) on the OPC drum. 
4
Transfer unit
Transfers toner images to the OPC drum. 
5
Main charger unit
Charges the OPC drum surface negatively and evenly. 
No.
Name
Functions
1
Laser beams
Forms electrostatic latent images on the OPC drum. (Writing resolution: 600dpi)
Radiated from the LSU. The output can be set with the simulation. (Basically not changed from the default.)
2
OPC drum
Electrostatic latent images are formed by laser beams. Toner is attracted to the latent electrostatic images 
and transferred to paper. An OPC drum is employed. The diameter is 80mm. 
3
Main charger
Applies a high voltage to charge the OLPC drum. The saw teeth type is employed. 
4
Screen grid
Carries electric charges from the main charger to the OPC drum evenly. 
5
MG roller
Forms a magnetic brush with developer, and applies toner to the OPC drum. -500V
6
Developing doctor
Keeps the thickness of developer or toner layer on the MG roller at a fixed level. 
7
Toner concentration sensor
Detects toner in the developing tank. The transmission type sensor is employed. 
-590v
-6.2kv(700
µ
A)
-2.0kv
-300v
+500v
-150v
AC4.5kv
(P-P)
+2.0kv
(35
µ
A)
(1.5 - 2.0kv)
10
8
Transfer belt
cleaning mode
Cleaning roller
cleaning mode
Cleaning mode
Transfer mode
Cleaning 
mode
Developing 
mode
4
3
5
1
3
6
8
2
9
11
12
10
7
AR-M550/M620  DETAILS OF EACH SECTION  6 - 64
[Toner hopper and toner bottle section] 
A. Outline
Adoption of the rotating toner bottle enables large capacity with a com-
pact toner bottle size. 
When the remaining toner detection sensor in the toner hopper unit
detects no toner, the toner bottle turns to supply toner to the toner hop-
per. Following supply, since the sensor detects full or empty status
inside the toner hopper based on a standard quantity of approximately
150 g of toner, even if the toner cartridge becomes empty, copying is
not immediately suspended because toner inside the toner hopper is
used (approximately 5K/6% print duty documents).
The employment of new toner has reduced the toner consumption per
page by 20 -30%.
8
Transfer roller
Applies a voltage to transfer toner from the OPC drum to paper. 
9
Drum separation pawl
Separates paper from the OPC drum mechanically. 
10
Cleaning blade
The protection circuit to prevent against electric leak of high voltage through the paper guide when the 
humidity is high. 200 Ohm each. 
11
Resist roller
Deflects paper to adjust the paper feed timing to the process section. 
12
Paper dust cleaner
Remove paper dust from the resist roller to reduce paper dust entry to the process section.
No.
Name
Functions
Destination
Toner filling amount
Life with 6% print duty 
documents
Except Japan
1,430g
72,000 sheets
Japan
Provisionally 1,180g
50,000 sheets or more

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