Sharp Mx-b200 Service Manual

							MX-B200  UNPACKING AND INSTALLATION  5 - 12 11) Attach the motor connector and the snap band to the original
position.
12) Attach the Scanner UPG mylar J3 to cover the hole on the right
side of inside of the scanner.
Note:The mylar should cover the hole shown by the arrow in
the diagram.
Attach along with the bent part of the metal plate and align the
edge of the mylar with the line shown in the diagram (the yellow
line in the diagram).
13) Attach the Fan housing cushion to the cooling fan at the posi-
tion shown in the diagram below.
Cover the top and the right side of the fan housing when you
see the fan housing from the backside of the machine.
Note:Please make sure the double-sided tape is not exposed
where the cushion is sticking out from the edge of the fan
housing.Attach the cushion leaving 3 - 7mm from the edge so that the
gap between the Fan housing cushion and the filter of the rear
cabinet is filled for sure.
14) Attach the parts removed in the items 1), 2), and 3).
A
View from
the arrow ABack side
Attach the cushion leaving3-7mm
from the edge.Reference position
3 - 7mm 
						

							MX-B200  COPY PROCESS  6 - 1
[6] COPY PROCESS
1. Functional diagram
(Basic operation cycle)
(20 microns thick)
Aluminum drum  Pigment layer (0.2
to 0.3 microns thick) An OPC drum is used for the photoconductor.
(Structure of the OPC drum layers)
OPC layer
Main charger
Laser beam
MG rollerCleaning blade
Drum
Transfer unit
Resist roller
Exposure Main high voltage unit
Saw toothCharge
Drum
Cleaning
Cleaning blade
Waste toner box
Paper release Fus ing
Separation
Heat roller
Heater lampTransferTransfer charger
Transfer high
voltage unitDeveloping
Toner
Developer
Pr int pr oc ess
Paper transport route
Semiconductor laser
Manual feed
PS roller
Focus correction lens
Electrode
Synchronizationwith drum
Cassettepaper feed
To face
down tray 
						

							MX-B200  COPY PROCESS  6 - 2
2. Outline of print process
This printer is a non-impact printer that uses a semiconductor
laser and electrostatic print process. This printer uses an OPC
(Organic Photo Conductor) for its photoconductive material.
First, voltage from the main corona unit charges the drum surface
and a latent image is formed on the drum surface using a laser
beam. This latent image forms a visible image on the drum surface
when toner is applied. The toner image is then transferred onto the
print paper by the transfer corona and fused on the print paper in
the fusing section with a combination of heat and pressure.
Step-1:Charge
Step-2:Exposure
* Latent image is formed on the drum.
Step-3:Developing
Latent image formed on the drum is then changed into
visible image with toner.
Step-4:Transfer
The visible image (toner image) on the drum is transferred
onto the print paper.
Step-5:Cleaning
Residual toner on the drum surface is removed and col-
lected by the cleaning blade.
Step-6:Optical discharge
Residual charge on the drum surface is removed, by
semiconductor laser beam.
3. Actual print process
Step-1: DC charge
A uniform negative charge is applied over the OPC drum surface
by the main charging unit. Stable potential is maintained by means
of the Scorotron charger.
Positive charges are generated in the aluminum layer.
Step-2: Exposure (laser beam, lens)
A Laser beam is generated from the semiconductor laser and con-
trolled by the print pattern signal. The laser writes onto the OPC
drum surface through the polygon mirrors and lens. The resis-
tance of the OPC layer decreases for an area exposed by the
laser beam (corresponding to the print pattern signal). The beam
neutralizes the negative charge. An electrostatic latent image is
formed on the drum surface.
About
DC5.5KV
(   580V/   400V)
OPC layer
Pigment
layer
Aluminum
drum
OPC layer
Pigment
layer
Aluminum
layer Drum surface charge
after the exposure
Non-image area Image areaSemiconductor laser
Exposure
(semiconductor laser) 
						

							MX-B200  COPY PROCESS  6 - 3 Step-3: Developing (DC bias)
A bias potential is applied to the MG roller in the two component
magnetic brush developing method, and the toner is charged nega-
tive through friction with the carrier.
Non-image area of the drum surface charged with negative
potential repel the toner, whereas the laser exposed portions
where no negative charges exist, attract the toner. As a result, a
visible image appears on the drum surface.
Toner is attracted over the shadowed area because of the develop-
ing bias.Step-4: Transfer
The visible image on the drum surface is transferred onto the print
paper by applying a positive charge from the transfer corona to the
backside of the print paper.
Step-5: Separation
Since the print paper is charged positively by the transfer corona, it
is discharged by the separation corona. The separation corona is
connected to ground.
Step-6: Cleaning
Toner remaining on the drum is removed and collected by the
cleaning blade. It is transported to the waste toner collecting sec-
tion in the cleaning unit by the waste toner transport roller.
S
N
N
:Carrier (Magnetized particle)
:Toner (Charge negative by friction)
(N) (S) Permanent magnet
(provided in three locations)
MG roller DC
400V   8V
About DC 5.2kV 
						

							MX-B200  COPY PROCESS  6 - 4 Step-7: Optical discharge (Semiconductor laser)
Before the drum rotation is stopped, the semiconductor laser is
radiated onto the drum to reduce the electrical resistance in the
OPC layer and eliminate residual charge, providing a uniform state
to the drum surface for the next page to be printed.
When the electrical resistance is reduced, positive charges on the
aluminum layer are moved and neutralized with negative charges
on the OPC layer.
Charge by the Scorotron charger
Function
The Scorotron charger functions to maintain uniform surface
potential on the drum at all times, It control the surface potential
regardless of the charge characteristics of the photoconductor.
Basic function
A screen grid is placed between the saw tooth and the photocon-
ductor. A stable voltage is added to the screen grid to maintain the
corona current on the photoconductor.
As the photoconductor is charged by the saw tooth from the main
corona unit, the surface potential increases. This increases the
current flowing through the screen grid. When the photoconductor
potential nears the grid potential, the current turns to flow to the
grid so that the photoconductor potential can be maintained at a
stable level.
Process controlling
Function
The print pattern signal is converted into an invisible image by the
semiconductor laser using negative to positive (reversible) devel-
oping method. Therefore, if the developing bias is added before
the drum is charged, toner is attracted onto the drum. If the devel-
oping bias is not added when the drum is charged, the carrier is
attracted to the drum because of the strong electrostatic force of
the drum.
To avoid this, the process is controlled by adjusting the drum
potential and the grid potential of the Scorotron charger.
Basic function
Voltage added to the screen grid can be selected, high and low. To
make it easily understood, the figure below shows voltage transi-
tion at the developer unit.
Start
1) Because the grid potential is at a low level, the drum potential
is at about -400V. (Carrier may not be attracted though the car-
rier is pulled towards the drum by the electrostatic force of -
400V.
2) Developing bias (-400V) is applied when the photoconductor
potential is switched from LOW to HIGH.
3) Once developing bias (-400V) is applied and the photo conduc-
tor potential rises to HIGH, toner will not be attracted to the
drum.
Stop
The reverse sequence takes place.
Retaining developing bias at an abnormal occurrence
Function
The developing bias will be lost if the power supply was removed
during print process. In this event, the drum potential slightly
abates and the carrier makes deposits on the drum because of
strong static power. To prevent this, the machine incorporates a
function to retain the developing bias for a certain period and
decrease the voltage gradually against possible power loss.
Basic function
Normally, the developing bias voltage is retained for a certain time
before the drum comes to a complete stop if the machine should
stop before completing the normal print cycle. The developing bias
can be added before resuming the operation after an abnormal
interruption. Therefore, carrier will not make a deposit on the drum
surface.
Semiconductor laser
0START STOPPrint potential
Toner attract
potential
2)
3)
1)Low
4)Hi ghDrum potential
Developing bias
Time 
						

							MX-B200  OPERATIONAL DESCRIPTIONS  7 - 1
[7] OPERATIONAL DESCRIPTIONS
1. Outline of operation
The outline of operation is described referring to the basic configuration.
(Basic configuration)
(Outline of copy operation)
Setting conditions
1) Set copy conditions such as the copy quantity and the copy
density with the operation section, and press the Start key. The
information on copy conditions is sent to the MCU.
Image scanning
2) When the Start key is pressed, the scanner section starts scan-
ning of images. 
The light from the copy lamp is reflected by the document and
passed through the lens to the CCD.
Photo signal/Electric signal conversion
3) The image is converted into electrical signals by the CCD circuit
and passed to the MCU.
Image process
4) The document image signal sent from the CCD circuit is pro-
cessed under the revised conditions and sent to the LSU (laser
unit) as print data.
Electric signal/Photo signal (laser beam) conversion
5) The LSU emits laser beams according to the print data.
(Electrical signals are converted into photo signals.)
6) The laser beams are radiated through the polygon mirror and
various lenses to the OPC drum.Printing
7) Electrostatic latent images are formed on the OPC drum
according to the laser beams, and the latent images are devel-
oped to be visible images (toner images).
8) Meanwhile the paper is fed to the image transfer section in syn-
chronization with the image lead edge.
9) After the transfer of toner images onto the paper, the toner
images are fused to the paper by the fusing section. The copied
paper is discharged onto the exit tray.
(Outline of printer operation)
The print data sent from the PC are passed through the USB con-
nector and the MCU to the LSU. The procedures after that are the
same as above 5) and later.
(Outline of scanner operation)
The scan data are passed through the MCU to the PC according
to the conditions requested by the operations with the operation
panel.
Operation
sectionScanner sectionCCD 
MCU (Main control/image process section)
USBPC
Laser beam
Paper exit
Fusing section
Paper transport section
Manual paper
feed section Cassette paper
feed section Printer sectionLSU (Laser unit)
Laser diode, Polygon mirror lens
Process section 
						

							MX-B200  OPERATIONAL DESCRIPTIONS  7 - 2
2. Scanner section
A. Scanner unit
The scanner unit in the digital copier scans images.
It is composed of the optical unit and the drive unit. The optical unit
performs scanning in the main scan direction with the light receiving
elements (color CCD). The drive unit performs scanning in the sub
scanning direction by moving the optical unit.
B. Optical system
Two white lamps are used as the light source.
Light radiated from the light source is applied to the document on
the document table. The reflected light from the document is
reflected 4 times by No. 1 - No. 3 mirrors and passed through the
reduction lens to form images on the light-receiving surface of 3-line
CCD.
The light-receiving surface of the color CCD is provided with 3 line
scanning sections for RGB. Separate images scanned in each color
section are overlapped to complete color scanning. (When PC
scanning)
The resolution is 600dpi.
When copying, only the green component is used to print with the
printer.
The color component for printing can be switched to red or blue by
the service simulation.
(Spectrum characteristics of the lamp)(Spectrum characteristics of the color CCD)
(Optical unit)
C. Drive system
The drive system is composed of the scanner motor, the pulley
gear, the idle pulley, the idle gear, the belt 473, the belt 190, and
the shaft.The motor rotation is converted into reciprocated movements of the
belt 473 through the idle gear, the pulley gear, the belt 190, and the
idle pulley to drive the optical unit.
100
75
50
45.4100.0
50.2
25
380
480
580
680
780
Wavelength [nm]
Sensitivity
1 Table glass 2 Optical unit 3 Lens
4 Mirror 1 5 Mirror 2 6 Mirror 3
7 CCD PWB 8 Lamp 9 Reflector
10 Original
Spectral sensitivity characteristics (Standard characteristics)
Relative sensitivity
Wavelength [nm]
8998101
7
5
342
6
79
34 6 28 51
3
1 Scanner motor 2 Pulley gear 3 Idle pulley
4 Belt 473 5 Belt 190 6 Optical unit
7 Shaft 8 Idle gear 9 Table glass 
						

							MX-B200  OPERATIONAL DESCRIPTIONS  7 - 3
3. Laser unit
The image data sent from the MCU (image process circuit) is sent
to the LSU (laser unit), where it is converted into laser beams.
A. Basic structure
The LSU unit is the writing section of the digital optical system.
The semiconductor laser is used as the light source, and images
are formed on the OPC drum by the polygon mirror and fθ lens, etc.
The laser beams are passed through the collimator lens, the cylin-
drical lens, the polygon mirror, the fθ lens, and the mirror to form
images on the OPC drum in the main scanning direction. The laser
emitting PWB is provided with the APC (auto power control) in order
to eliminate fluctuations in the laser power. The BD PWB works for
measurement of the laser writing start point.
Makes the laser scanning speeds at both ends of the drum same as
each other.
B. Laser beam path
C. Composition
Effective scanning width:216mm (max.)
Resolution:600dpi
Beam diameter:75um in the main scanning direction, 85um in the
sub scanning direction
Image surface power:0.16 ± 0.01mW (Laser wavelength 770 -
795nm)
Polygon motor section:Brushless motor 35433rpm
No. of mirror surfaces:5 surfaces
4. Fuser section
* SPF is option. No  Component Function
1 Semiconductor laser Generates laser beams.
2 Collimator lens Converges laser beams in parallel.
3 Cylinder lens Takes the focus.
4 Polygon mirror, 
polygon motorReflects laser beams at a constant 
rpm.
5 BD (Lens, PWB) Detects start timing of laser 
scanning.
6fθ lens Converges laser beams at a spot on 
the drum.
Makes the laser scanning speeds at 
both ends of the drum same as each 
other. (Refer to the figure below.)
2
3 3
6 41
5
6
a ≠ b ≠ c
ab c
d = e = f
def
  fθ LENS 
						

							MX-B200  OPERATIONAL DESCRIPTIONS  7 - 4
A. General description
General block diagram (cross section)
Top view
(1) Heat roller
A Teflon roller is used for the heat roller and a silicone rubber roller
is used for the lower heat roller for better toner fusing performance
and paper separation.
(2) Separator pawl
Three separator pawls are used on the upper heat roller. The sep-
arator pawls are Teflon coated to reduce friction with the roller and
prevent a smear on the paper caused by the separator pawl.
(3) Thermal control
1) The heater lamp, thermistor, main PWB, DC power supply
PWB, and triac within the power supply unit are used to control
the temperature in the fuser unit.
To prevent against abnormally high temperature in the fuser
unit, a thermal breaker and thermal fuse are used for safety
purposes.2) The surface temperature of the upper heat roller is set to 160 -
200°C. The surface temperature during the power save mode is
set to 100°C.
3) The self-check function comes active when one of the following
malfunctions occurs, and an H is displayed on the multicopy
window.
a. When the heat roller surface temperature rises above 240°C.
b. When the heat roller surface temperature drops below 100°C
during the copy cycle.
c. Open thermistor
d. Open thermal fuse
e. When the heat roller temperature does not reach 190°C within
27 second after supplying the power.
(4) Fusing resistor
This model is provided with a fusing resistor in the fusing section
to improve transfer efficiency.
Since the upper heat roller is conductive, when using copy paper
that contains moisture and the distance between the transfer unit
and the fusing unit is short, the transfer current may find a path to
ground via the copy paper, the upper heat roller and the discharg-
ing brush.
5. Paper feed section and paper 
transport section
A. Paper transport path and general operations
* SPF is option.
Paper feed is made in two ways; the tray paper feed and the man-
ual paper feed. The tray is of universal-type, and has the capacity
of 250 sheets.
The front loading system allows you to install or remove the tray
from the front cabinet.
The general descriptions on the tray paper feed and the manual
paper feed operation are given below.
Separator pawl
PPD2
Thermal fuse
Thermistor
Heat roller
Paper guide
Pressure roller
Heat rollerThermistorThermal fuse
Heater lamp
Separator pawl
Safety device
(thermal breaker, thermal
fuse)
Triac (in t he
power supply unit)Heated by the heater 
lamp. (800W)
The surface temperature
of the upper heat roller is
sensed by the thermistor.
Level of the thermistor is
controlled by the main PWB.
With the signal from the
main PWB, the triac is
controlled on and off.
(power supply PWB)
1 Scanner unit 8 Drum
2 Copy lamp 9 Transfer unit
3 LSU (Laser unit) 10 Pickup roller
4 Paper exit roller 11 Manual paper feed tray
5 Main charger 12 Manual paper feed roller
6 Heat roller 13 PS roller unit
7 Pressure roller 14 Paper feed roller
1 2 5 3 4
6
7
8
9
10
11
12 13 14 
						

							MX-B200  OPERATIONAL DESCRIPTIONS  7 - 5
(1) Cassette paper feed operation
1) The figure below shows the positions of the pick-up roller, the
paper feed clutch sleeve, and the paper feed latch in the initial
state without pressing the Start key after lighting the ready
lamp.
The paper feed latch is in contact with the projection of the
clutch sleeve.
2) When the Start key is pressed, the main drive motor starts
rotating to drive each drive gear.
The pick-up drive gear also is driven at that time. Since, how-
ever, the paper feed latch is in contact with the projection of the
clutch sleeve, rotation of the drive gear is not transmitted to the
pick-up roller, which does not rotate therefore.
3) After about 0.1 sec from when the main motor start rotating, the
tray paper feed solenoid (PFS) turns on for a moment.
This disengages the paper feed latch from the projection of the
clutch sleeve, transmitting rotation of the pick-up drive gear to
the paper feed roller shaft, rotating the pick-up roller to feed the
paper.
4) After more than half rotation of the pick-up roller, the paper feed
latch is brought in contact with a notch on the clutch sleeve,
stopping rotation of the pick-up roller.5) At this time, the paper is fed passed the paper entry detection
switch (PPD1), and detected by it. After about 0.15 sec from
detection of paper by PPD1, the tray paper feed solenoid (PFS)
turns on so that the clutch sleeve projection comes into contact
with the paper feed latch to stop the pick-up roller. Then the
pick-up roller rotates for about 0.15 sec so that the lead edge of
the paper is evenly pressed on the resist roller, preventing
against skew feeding.
6) To release the resist roller, the tray paper feed solenoid and the
resist solenoid are turned on by the paper start signal to disen-
gage the resist start latch from the clutch sleeve, transmitting
rotation of the resist drive gear to the resist roller shaft. Thus
the paper is transported by the resist roller.
7) After the resist roller starts rotating, the paper is passed through
the pre-transfer guide to the transfer section. Images are trans-
ferred on the paper, which is separated from the OPC drum by
the drum curve and the separation section.
8) The paper separated from the drum is passed through the fus-
ing paper guide, the heat roller (fusing section), POD (paper out
detector) to the copy tray.
OFFPFS
OFF RRS
OFFPFS
OFF RRS
ON PFS
OFF RRS
OFFPFS
ON RRS