Oki MB280 User manual

MB280 / MB290
SERVICE MANUAL

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
i
TABLE OF CONTENTS
1. DETAILED SECTION DESCRIPTIONS.......................................1-1
1.1 COMPONENT LAYOUT.......................................................................... 1-1
1.1.1 MECHANICAL COMPONENTS...................................................... 1-1
1.2 PRINTING............................................................................................... 1-2
1.2.1 PRINTING PROCESSES AROUND THE DRUM............................ 1-2
1.2.2 CHARGE........................................................................................ 1-3
1.2.3 LASER EXPOSURE....................................................................... 1-4
Overview............................................................................................. 1-4
Block Diagram .................................................................................... 1-5
Error Conditions.................................................................................. 1-5
1.2.4 DEVELOPMENT............................................................................. 1-6
Overview............................................................................................. 1-6
Toner End Detection........................................................................... 1-8
1.2.5 TRANSFER AND SEPARATION.................................................... 1-9
Overview............................................................................................. 1-9
Cleaning Mode.................................................................................... 1-9
1.2.6 DRUM CLEANING........................................................................ 1-10
1.2.7 PAPER FEED AND REGISTRATION........................................... 1-11
Overview........................................................................................... 1-11
Paper Feed Drive Mechanism........................................................... 1-12
Paper Feed Operation ...................................................................... 1-13
Registration ...................................................................................... 1-14
Paper End Detection......................................................................... 1-15
Jam Detection................................................................................... 1-16
1.2.8 FUSING........................................................................................ 1-17
Overview........................................................................................... 1-17
Power Save Control.......................................................................... 1-18
1.2.9 COVER SWITCH.......................................................................... 1-19
1.2.10 PAPER FEED DRIVE RELEASE AND FUSING
DRIVE RELEASE.................................................................... 1-20
2. REPLACEMENT AND ADJUSTMENT........................................2-1
2.1 PAPER CASSETTE ................................................................................ 2-2
2.1.1 PAPER CASSETTE........................................................................ 2-2
Side Fence ......................................................................................... 2-2
Bottom Plate....................................................................................... 2-3
Friction Pad ........................................................................................ 2-3
2.2 LASER UNIT........................................................................................... 2-4
2.3 FUSING AREA........................................................................................ 2-6
2.3.1 FUSING UNIT................................................................................. 2-6
2.3.2 PAPER EXIT ASSEMBLY .............................................................. 2-7
2.3.3 FUSING LAMP AND HOT ROLLER ............................................... 2-8
Fusing Lamp....................................................................................... 2-8
Hot Roller............................................................................................ 2-9
2.3.4 PRESSURE ROLLER................................................................... 2-10

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
ii
2.3.5 THERMISTOR.............................................................................. 2-11
2.3.6 HOT ROLLER STRIPPERS.......................................................... 2-11
2.3.7 THERMOSTAT............................................................................. 2-12
2.4 PAPER FEED........................................................................................ 2-13
2.4.1 PAPER FEED ROLLER REMOVAL.............................................. 2-13
2.4.2 REGISTRATION ROLLER............................................................ 2-15
(ALSO KNOWN AS ‘ROLLER DRIVEN’ IN THE PARTS CATALOG) 2-15
2.5 OTHERS............................................................................................... 2-16
2.5.1 TRANSFER ROLLER................................................................... 2-16
2.5.2 FAN MOTOR................................................................................ 2-17
2.5.3 MAIN MOTOR REMOVAL............................................................ 2-18
2.5.4 DISCHARGE LAMP ASSY........................................................... 2-19
2.6 PSU (KNOWN AS ‘POWER SUPPLY UNIT’
IN THE PARTS CATALOG)................................................................. 2-20
2.6.1 PSU REMOVAL ............................................................................ 2-20

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
6 September 2005
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1-1
Detailed
Descriptions
1. DETAILED SECTION DESCRIPTIONS
1.1 COMPONENT LAYOUT
1.1.1 MECHANICAL COMPONENTS
No. Name Description
A Laser Unit Consists of the laser diode unit, cylindrical lens, f-theta
lens, polygon mirror motor, and other laser optical
components.
B Toner Cassette Consists of the OPC drum, toner, toner application roller,
development roller, charge brush roller, cleaning blade,
and other development components.
C Upper Tray Bottom Plate Presses paper stacked in the upper paper tray against the
paper feed roller.
D Paper Feed Roller Picks up the top sheet of paper from the stack in the
upper paper tray and feeds it into the transfer area.
E Transfer Roller Applies a charge to the paper to pull the toner off the drum
and onto the copy paper.
F Pressure Roller Applies pressure to the paper during fusing.
G Hot Roller Fuses the toner to the copy paper.
H Paper Exit Roller Feeds the paper out of the printer.
G182D101.WM
F
A
B
C
DEF
GH

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
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1-2
1.2 PRINTING
1.2.1 PRINTING PROCESSES AROUND THE DRUM
This machine uses a “write to black” system, using negative toner.
Charge: The charge brush roller [A] gives the OPC drum [B] surface a negative
charge.
Exposure: A laser [C] writes a latent image on the drum. The charge in the area
exposed by the laser beam drops.
Development: The development roller [D] carries toner to the drum and develops
the latent image on the drum. The following charges are applied.
Development bias (during printing):
Toner application roller [E]
Development roller [D]
Switching bias (At the start and the end of any print process):
Toner application roller [E]
Development roller [D]
Image Transfer: The transfer roller [F] pulls the toner from the drum onto the
paper [G].
Paper Separation: The antistatic brush [H] removes the charge on the underside
of the paper to help the paper separate from the drum.
Drum Cleaning: The Discharge Lamp[L] discharge the OPC drum [B] surface,
The cleaning blade [J] removes any toner remaining on the drum
after the image is transferred to paper.
The high voltages [K] are supplied from the Power Supply Unit board.
G182D010.WMF
[A]
[B] [C]
[D]
[E][F]
[G]
[H]
[J] [K]
[K]
[L]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
6 September 2005
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1-3
Detailed
Descriptions
1.2.2 CHARGE
The OPC (Organic Photoconductor) drum [A] used in this machine is small in
diameter. This allows a very compact design.
A charge roller [B] charges the photoconductor. The charge roller has the
advantage of not generating ozone. A large negative voltage is applied from the
Power Supply Unit board to the charge roller. This charge roller gives the OPC
drum surface a negative charge.
The voltage to the charge roller is supplied through the terminal [C] from the Power
Supply Unit board.
G182D102.WMF
G182D003.WMF
[C]
[A]
[B]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
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1-4
1.2.3 LASER EXPOSURE
Overview
Laser Unit Layout
A : Laser Diode Unit F : Laser Synchronization Detector
B : Polygon Mirror Motor G : Cylindrical Lens
C : F-theta Lens H : Synchronization Detector Lens
D : First Mirror J : Shutter
E : Second Mirror
This machine uses a laser diode to produce an electrostatic latent image on the
OPC drum. The laser diode unit converts image data into laser pulses, and the
optical components direct these pulses to the OPC drum.
As a mechanical safety feature, the shutter [J] closes to block the laser beam path
whenever the front door is opened.
G182D004.WMF
[A]
[B]
[C] [D]
[E]
[F]
[G]
[H]
[J]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
6 September 2005
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1-5
Detailed
Descriptions
Block Diagram
The Engine Board controls the laser diode power (APCSH) and transfers data for
printing to the laser diode (VIDEO). As an electrical safety feature, there is an
interlock switch on the Engine Board. This switch cuts +24 volts whenever the front
door is opened.
Error Conditions
Laser Error
The machine detects laser synchronization signal pulses (PGSYCI) 70 milliseconds
after the (LDENA) signal is sent. It detects a laser error if the pulse count does not
reach the specified number within 400 milliseconds.
When this occurs, the machine warns the customer on the LCD panel (Error 56).
Polygon Mirror Motor Error
The machine detects a polygon mirror motor error when the (PMLOK) signal does
not go low within 3.5 seconds of the (PMENA) signal. When this occurs, the
machine warns the customer on the LCD panel (Error 57).
Laser Diode Unit
Laser Diode
Driver
Laser Diode
Laser
Synchronization
Detector
Polygon Mirror
Motor Unit
Polygon Mirror
Motor Driver
Regulator
Engine Board
Power
Supply
Unit
+5V
VIDEO
LDENA
APCSH
PGSYCI
+24VD
PMENA
PMCLK
PMLOK
+24V
Interlock Switch
G182D012.WMF

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
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1-6
1.2.4 DEVELOPMENT
Overview
This machine uses mono-component toner, which is composed of resin and ferrite.
The toner mixing bar [A] stirs and carries toner to the toner application roller [B].
The toner application roller supplies toner to the development roller [C]. As the
development roller turns past the toner metering blade [D], only a thin coating of
negatively charged toner particles stays adhered to the development roller.
During printing, a bias voltage is applied to the toner application roller and another
bias voltage is applied to the development roller. The toner is transferred from the
toner application roller to the development roller by the potential difference
between these two rollers.
The development roller applies toner to the exposed areas of the latent image as
they turn past the drum.
G182D103.WM
F
[A]
[B]
[C] [D]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
6 September 2005
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1-7
Detailed
Descriptions
The voltage to the development roller and the toner application roller is supplied
through the terminals ([A] for the development roller and [B] for the toner
application roller) from the Power Supply Unit board.
G182D005.WMF
[A]
[B]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
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1-8
Toner End Detection
This machine does not have toner end detection.

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
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TECHNICAL DOCUMENT
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1-9
Detailed
Descriptions
1.2.5 TRANSFER AND SEPARATION
Overview
This machine uses a transfer roller [A], which touches the OPC drum [B] surface. A
constant current is applied to the transfer roller from the power supply unit board
[C]. The positively-biased transfer roller pulls negatively-charged toner off the drum.
The curvature of the drum, and the antistatic brush [D], help the paper [E] to drop
away from the drum.
Cleaning Mode
If a paper jam occurs during printing, toner may be transferred to the transfer roller
surface. To prevent this toner from transferring to the underside of the paper, the
transfer roller must be cleaned before the next printing run.
While the machine is in the cleaning mode, the Power Supply Unit board applies a
negative voltage to the transfer roller.
The negatively charged toner on the transfer roller is then transferred back to the
drum.
The machine goes through the cleaning mode at the following times.
•At power-up: The process starts when the fusing temperature reaches the
standby temperature.
•When the cover is opened and then closed during the printing process.
•After a printer jam has been cleared.
G182D104.WMF
[A]
[B]
[C]
[D]
[E]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
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1-10
1.2.6 DRUM CLEANING
The cleaning blade and the used toner tank are contained in the toner cartridge.
The Discharge Lamp and A counter blade system is used for drum cleaning. The
Discharge Lamp[C] discharge the drum surface. The cleaning blade [A] removes
any toner remaining on the drum after the image is transferred to the paper. This
removed toner is stored in the used toner tank [B].
There is no used toner overflow detection mechanism, because the used toner
tank is large enough for the lifetime of the toner cassette.
G182D102.WMF
[A]
[B]
[C]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
6 September 2005
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1-11
Detailed
Descriptions
1.2.7 PAPER FEED AND REGISTRATION
Overview
Paper Feed System: Feed roller [A] and Friction pad [B]
Paper Lift Mechanism: Bottom plate with spring [C]
Sheet feeder 1 sheet feeder [D]
Tray Capacity: 250 sheets [E]
Paper End Detection: Paper end sensor
Paper Size Detection: None
G182D105.WMF
[A]
[B]
[C]
[D]
[E]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
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1-12
Paper Feed Drive Mechanism
The feed roller [A] is located above the upper tray bottom plate [B], and the friction
pad [C]. It allows only one sheet to feed from the paper tray. They are controlled by
the paper feed clutch [D]. The registration sensor detects the leading edge of the
paper and synchronizes paper feed with the activation of the laser diode to write
the image on the OPC drum.
G182D006.WMF
[A]
[B]
[C]
[D]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
TECHNICAL DOCUMENT
6 September 2005
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1-13
Detailed
Descriptions
Paper Feed Operation
A : Paper feed drive gear D : Friction pad
B : Paper feed clutch E : Paper feed sensor
C : Paper feed roller F : Registration sensor
The paper feed drive gear [A] always rotates while the main motor rotates, since
the paper feed clutch (magnet clutch) [B] is energized to turn the paper feed roller
[C].
When the paper feed clutch [B] is energized to turn the feed roller, the paper feed
roller feeds one sheet of paper from the tray. The paper is fed into the machine by
the registration roller.
G182D007.WMF
[A]
[B]
[C]
[D] [E]
[F]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
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1-14
Registration
The registration sensor [A] detects the leading edge of the paper and synchronizes
paper feed with the writing of the image on the drum, so that the image and paper
match up properly. This sensor also detects paper feed jams.
G182D107.WMF
[A]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
SERVICE MANUAL
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6 September 2005
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1-15
Detailed
Descriptions
Paper End Detection
The laser unit [A] has the paper end sensor [B] built into it. The paper end sensor
detects the presence or absence of paper. The sensor has an actuator that
extends through a slot in the paper tray bottom plate [C], so that the sensor is
actuated when paper is placed in the upper tray.
When the upper tray runs out of paper, the actuator of the paper end sensor moves
into the slot in the upper tray bottom plate. This informs the CPU that paper has run
out.
G182D008.WMF
[A]
[B]
[C]

PRINTER 3000 304 995 - 01
i
PRINTER MODEL-L1
 （
G191
）
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1-16
Jam Detection
Jam 1. Paper jam at the paper cassette
When the registration sensor does not turn on within 2.52 seconds after the paper
pick-up clutch for the paper cassette turns on.
Jam 2. Paper did not pass the registration sensor
When the registration sensor does not turn off within the specified time for passing
each paper size (see below) + 3 seconds after the registration sensor turns on.
Paper
Size A4SEF A5SEF A5LEF A6SEF B5SEF B6SEF Letter
SEF Legal SEF Envelope
(91x191mm)
Specified
Time
(msec) 2555 1807 1273 1273 2211 1566 2400 3059 1643
Jam 3. Paper did not reach the fusing unit
When the paper exit sensor does not turn on within 1.94 seconds after the
registration sensor turns on.
Jam 4. Paper jam in the fusing exit area
When the paper exit sensor does not turn off within 2.99 seconds after the
registration sensor turns off.
Jam 5. Paper no feed jam in the bypass tray
When the registration sensor does not turn on within 1.72 seconds after the main
motor starts.

PRINTER 3000 304 995 - 01
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PRINTER MODEL-L1
 （
G191
）
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6 September 2005
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1-17
Detailed
Descriptions
1.2.8 FUSING
Overview
After the image is transferred, the copy paper enters the fusing unit. The image is
fused to the copy paper by applying heat and pressure through the use of a hot
roller [A] and pressure roller [B].
The CPU monitors the hot roller temperature through a thermistor [C] that is in
contact with the hot roller surface. A thermostat [D] protects the fusing unit from
overheating.
The hot roller strippers [E] separate the copy paper from the hot roller and direct it
to the exit rollers [F]. The paper feed/exit sensor [G], which is under the fusing unit,
monitors the progress of the copy paper through the fusing unit and detects
misfeeds. The exit rollers [F] drive the copy paper to the paper output tray.
Springs [H] at the front and rear apply the proper fusing pressure between the hot
roller and pressure roller.
The fusing lamp [K] is located in the hot roller.
G182D106 WMF
[A]
[B]
[C]
[D]
[E]
[F]
[G]
[H]
K