OKI 320-321 Service Manual
OKI 320-321 Service Manual
OKI 320-321 Service Manual
ML320/ML321
Dot Matrix Printers
Note: This Adobe Acrobat version of the Okidata Service Training Manual was built with the
pictures rendered at 300 dpi, which is ideal for printing, but does not view on most
displays well.
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Table of Contents Page
Manual Copyright
This document may not be reproduced without written permission of the Okidata® Technical
Training Group. Every effort has been made to ensure the accuracy of the information
contained in this training course. Okidata is not responsible for errors beyond its control.
P/N 59231501 First Edition May, 1988 Microline 320/321 Training Manual
P/N 59231501 [Second Release May, 1990] Microline 320/321 Training Manual
P/N 59263401 First Edition February, 1994 Microline 320/321 Service Handbook
P/N 59263401 Second Revision July, 1994 Microline 320/321 Service Handbook
Okidata
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Service Guide ML320/ML321
Chapter 1 Product Specifications
The Microline 320 and Microline 321 are nine pin, dot matrix printers. Two versions of the printers
are available. The first provides Microline emulation. The second version provides Epson and IBM
Proprinter emulations, which are selected through the Printer Menu.
The major difference between the Microline 320 and Microline 321 is the width of each printer. The
Microline 320 can handle 80 print columns (at 10 CPI). The Microline 321 can print up to 136 columns
(at 10 CPI).
The standard interface is a Centronics parallel and an optional RS232-C serial interface can be
installed. The optional serial interface can transfer data at speeds up to 19.2K baud.
Both printers feature an enhanced operator panel which provides access to the following
capabilities.
Menu Selection
Quiet Mode
Printer Tests
Paper Park
Print Characteristics
Standard Printer Controls
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Service Guide ML320/ML321
Chapter 1 Product Specifications
A
Rev A units are original production units. An interconnect module connects the power supply board
to the main control board.
B
Rev B units are retrofitted to include a modified interconnect module, which prevents corrosion.
C
Rev C units have a cable harness connection between the power supply board and the main control
board. The cable harness replaces the interconnect module.
D
Rev D units have no power supply board. The circuitry for the power supply board has been
incorporated on the main control board.
The Rev A and Rev B main control board (LXMC) and power supply board (PAII) cannot be used
in Rev C units.
Rev D units do NOT use Rev A, Rev B, or Rev C main control boards, transformers, operator panels,
upper covers, and lower covers. Rev D units have a unique main control board (LXMR), no power supply
board, a 50 volt transformer, and a unique operator panel (LXON).
NOTE:
Please refer to the parts lists (Appendix B( )) for parts differentiation. Please be sure of the parts you
need before ordering to avoid confusion and incorrect parts orders.
Transformer
Interconnect Module
Cable
Cable Guide
Covers
Chassis
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Service Guide ML320/ML321
Chapter 1 Product Specifications
Compatibility Chart
Interconnect Module
Cable
Cable Guide
Covers
Item Okidata Purpose / Function of Item A B C D
P/N
Chassis
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Service Guide ML320/ML321
Chapter 1 Product Specifications
Rev D
Super Speed Draft (SSD)
High Speed Draft (HSD)
Utility
Near Letter Quality (NLQ)
Epson/IBM Version
Character Set I
Character Set II
DLL (not available through Menu)
Character Pitch
Print Mode 10 cpi 12 cpi 17.1cpi 20 cpi
SSD N/A 360 cps N/A N/A
HSD 300 cps 300 cps 300 cps 300 cps
Utility 250 cps 250 cps 250 cps 250 cps
NLQ 62.5 cps 62.5 cps 62.5 cps 62.5 cps
Character Pitch
Print Mode 10 cpi 12 cpi 17.1cpi 20 cpi
HSD 100 dpi 120 dpi 171.4 dpi 200 dpi
Utility 120 dpi 144 dpi 205.7 dpi 240 dpi
NLQ 240 dpi 288 dpi 411.4 dpi 480 dpi
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.3.01 Width
Microline 320
Minimum: 3 inches (76.2 mm)
Maximum: 10 inches (254 mm)
Microline 321
Minimum: 3 inches (76.2 mm)
Maximum: 16 inches (406.4 mm)
1.3.09 Labels
1.3.10 Transparencies
Thickness
Maximum: 0.004 inches (0.10 mm)
Dimensions
Maximum: 8.5 inches wide x 11 inches long (216 mm x 260 mm)
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.4.02 Weight
Microline 320
Revs A, B, and C: 16 pounds
Rev D: 17.2 pounds (7.8 kg)
Microline 321
Revs A, B, and C: 20 pounds
Rev D: 22.2 pounds (10.1 kg)
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Service Guide ML320/ML321
Chapter 1 Product Specifications
Frequency
50/60 Hz +/- 2%
Revs A, B, and C
Operating: 315 VA
Idle: 80 VA
Rev D
Operating: 70 VA
Idle: 25 VA
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.6.01 Temperature
Operating
41 through 104 degrees Fahrenheit (5 to 40 degrees Celsius)
Non-Operating
14 through 109.4 degrees Fahrenheit (-10 to 43 degrees Celsius)
Storage
-40 through 158 degrees Fahrenheit (-40 to 70 degrees Celsius)
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.7.01 Listings
Revs A, B, C, and D
UL Standard No. 478
CSA Standard C22.2 No. 220
FCC Part 15, Subject J, Class B
Revs A, B, and C
VDE 0806, VDC 0875 Class B
BS5850
Rev D
VDE 0806, VFG 0243 Class B
BS7002
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.8 OPTIONS
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.9 CONSUMABLES
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Service Guide ML320/ML321
Chapter 1 Product Specifications
1.10.01 DRAM
60 Kbytes
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Service Guide ML320/ML321
Chapter 1 Product Specifications
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
This section describes the operation of the printer. It is divided into three parts.
2) Electrical Operation ( )
This section views the printer functions from an electrical perspective.
3) Mechanical Operation ( )
This section views the printer functions from a mechanical perspective.
B
Rev B units are retrofitted to include a modified interconnect module, which prevents corrosion.
C
Rev C units have a cable harness connection between the power supply board and the main control
board. The cable harness replaces the interconnect module.
D
Rev D units have no power supply board. The circuitry for the power supply board has been
incorporated on the main control board.
The Rev A and Rev B main control board (LXMC) and power supply board (PAII) cannot be used
in Rev C units.
Rev D units do NOT use Rev A, Rev B, or Rev C main control boards, transformers, operator panels,
upper covers, and lower covers. Rev D units have a unique main control board (LXMR), no power supply
board, a 50 volt transformer, and a unique operator panel (LXON).
NOTE:
Please refer to the parts lists (Appendix B) for parts differentiation. Please be sure of the parts you
need before ordering to avoid confusion and incorrect parts orders.
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Page: 18
Service Guide ML320/ML321
Chapter 2 Principles of Operation
Power Supply ( )
Control Board ( )
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
Rev A, B, C, and D
The operator panel board contains switches and LED's which allow the end user to control
and monitor the printer's operation. For specific information on the capabilities and use of
the operator panel, please refer to Chapter 4 ( ) in the Printer Handbook.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
Rev A, B, and C
The power supply consists of a power transformer, filter board and a DC power supply board.
The AC input voltage is stepped down to 8.6 VAC, 46 VAC and 10 VAC by the power transformer.
These AC voltages are converted into + 8 vdc, + 40 vdc, and + 5 vdc by the power supply board
for use throughout the printer.
Power Transformer
If the transformer temperature rises above a pre-determined level, the built-in temperature fuse
opens to prevent damage to components in the printer. Once this fuse opens, the transformer
MUST be replaced.
Filter Board
The power switch, line fuse, and line filter are mounted on the filter board.
Rev D
The power supply consists of the power transformer, a filter board, and power supply circuitry
(located on the main controller board).
The input AC voltage is stepped down to 8.6 VAC, 46 VAC, and 10 VAC by the power transformer.
These AC voltages are rectified into + 8 vdc, + 5 vdc, and + 50 vdc levels by the DC power supply
circuitry on the main controller board.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
Microprocessor
The microprocessor is the nucleus of the control circuitry. All peripheral circuits operate under
the control of the microprocessor.
For the Rev A, B, and C printers, the Program ROM is Q13 - 128 kilobytes.
Q12 has a battery backup. Data is retained even after power is removed.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
This is an external interface and motor control LSI. It performs the following functions.
I/O Ports
Control signals are sent in response to commands input from the microprocessor.
The input port is used to read information on the printer's condition.
Address Latch
It latches the low order eight bits of the address bus (A0 to A7). These bits are used as
addresses for read/write operations with peripheral devices.
Motor Controller
Spacing Motor Control
This function accelerates and decelerates the spacing motor in accordance
with commands from the microprocessor and controls the spacing motor
speed in various printing modes. Motor speed and direction are determined
by monitoring the signals PHASE A and PHASE B, which are provided by
the encoder on the spacing motor.
2.3.01 Initialization ( )
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
2.3.01 Initialization
In Rev A, B, and C printers, initialization occurs whenever the printer is powered ON or when the
signal I-PRIME is received at the parallel interface.
In Rev D printers, initialization occurs whenever the printer is powered ON, or when the RSTOUT
signal is sent from the reset circuit (Q11) Pin 2 to Q1 and Q3.
In Rev A, B, and C printers, Q7 and Q11 are reset. In Rev D printers, Q1 and Q3 are
reset.
In Rev A, B, and C printers, the operating modes of Q7 and Q11 are set. In Rev D printers,
the operating modes of Q1 and Q3 are set.
RAM is initialized.
Carriage homing is performed. The carriage will move to the left until it contacts the left
frame.
The program then establishes the interface signals (ACK, BUSY) and the SEL lamp lights.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
Parallel Interface
In Rev A, B, and C printers, the data from the host is input through connector CN5 to the
interface LSI Q11.
In Rev D printers, the data from the host is input through connector CN6 to the interface LSI Q3.
The interface LSI latches this input data in synchronization with the STB-N signal. The BUSY
signal is active while this data is being processed. When processing is complete, the BUSY signal
is turned OFF, and an ACK-N is sent to the host (to request more data).
The BUSY signal is also sent to the host whenever the printer is incapable of receiving data.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
This circuit drives the printhead coils (1 through 9) using the HD ON signal, along with the nine
HD DATA signals. The pulsewidth of HD ON determines the pin drive time. The pin drive time
increases as the number of pins to be driven increases. The pins are driven in synchronization with
the signal IPT, which is derived from the timing encoder (PHASE A and PHASE B) on the space
motor.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
The motor control LSI produces the spacing motor phase signals SP-U, SP-V, SP-W and the
overdrive signal SPD-A in accordance with spacing commands from the microprocessor.
The SPD-A signal is a fixed period pulse signal whose pulsewidth is controlled by the program. This
signal is used to control motor drive time.
As the spacing motor is driven, the signals PHASE-A and PHASE-B are generated by the
photosensor / encoder disk (which is mounted to the spacing motor).
The motor control LSI divides the frequency of these signals in accordance with the
selected print pitch. The LSI generates the IPT-N signal, which provides dot-on timing
and carriage position detection.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
During a line feed operation, the line feed motor is driven by the phase signals LF03
and LF04, in synchronization with the signal LFOVD.
When it is not being driven, the line feed motor is held in place by the LF HOLD signal.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
Printhead temperature rises when the unit is printing. When printhead temperature reaches 110
degrees Celsius, the HEAD OVERHEAT alarm is generated. Printing stops when this alarm is
detected. This allows the printhead temperature to fall. When the printhead temperature falls
below the alarm detection level, printing is resumed.
When the temperature of the printhead rises, the resistance of the thermistor decreases and the
potential falls at the negative input of comparator Q6. Q6 is located on the main controller board.
This inverts the comparator output, causing the HEAD TEMP signal to be sent to the motor control
LSI.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
2.4.01 Printhead
The printhead used by the printer is a highly efficient, stored-energy type. Power is not consumed
until the pins are activated. Printhead life is approximately 200 million characters.
The printhead is designed with nine pins, vertically aligned. Each pin is welded to an armature ring.
Behind the armature ring is a spacer ring.
Each armature has a permanent magnet behind it. The magnet attracts the armature, keeping the
pin inside the printhead. Because of the spacer ring behind the armature ring, the armature is
attracted toward the permanent magnet at an angle. A coil is wrapped around each permanent
magnet.
When a dot is printed, current passes through the coil, creating a magnetic field which counters
the magnetic field of the permanent magnet. The armature and pin spring forward. A dot is printed
on the paper.
When current is removed from the coil, the magnetic field of the permanent magnet attracts the
armature. The pin is retracted into the printhead.
The printhead contains a built-in thermistor (rated at 110 degrees Celsius). The thermistor
monitors the printhead temperature. If the temperature exceeds the 110 degrees Celsius,
the thermistor causes a signal to be generated on the main controller board. The printer
stops printing. A BUSY signal is sent to the host computer. Data remains in the print buffer
as long as power is supplied to the printer. When the printhead temperature drops below
the 110 degree Celsius threshold, the BUSY signal to the host computer becomes inactive.
Printing is resumed.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
The spacing operation is performed by applying power to the DC spacing motor. This drives the
carriage frame along the carriage shaft, space rack, and guide rail. The carriage shaft, space rack,
and guide rail are parallel to the platen.
DC Motor / Gear
Carriage Frame
Carriage Shaft
Space Rack
Encoder Disk Sensor
Encoder Disk
Guide Rail
Spacing Operation
The printhead and spacing motor are mounted on the carriage frame. The carriage frame
moves along the carriage shaft, space rack, and guide rail. The carriage shaft, space rack,
and guide rail are parallel to the platen. As the spacing motor rotates counterclockwise,
the carriage frame is driven to the right.
When the spacing motor rotates one turn, the carriage frame moves 0.8 inch (20.32 mm).
Motor rotation turns the encoder disk. The timing windows on the disk then pass through the
encoder disk sensor. The position of the carriage frame is obtained by counting the pulses
generated by the encoder disk sensor as the disk turns.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
The head gap adjusting mechanism adjusts the gap between the platen and printhead by changing
the tilt angle of the carriage frame. This is accomplished by using the adjusting lever.
Moving the adjusting lever rotates the adjusting screw. The adjusting screw is interlocked with the
lever via a gear. Rotating the adjusting screw changes the angle of tilt for the carriage frame. The
printhead is mounted vertically on the carriage frame. Changing the angle of tilt for the carriage
frame moves the printhead closer to, or farther away from, the platen.
The adjusting cam is used to compensate for differences in the printhead gap when measured at
the left and right sides of the platen. Rotating the adjusting cam changes the height of the guide
rail. The height of the guide rail helps determine the distance between the printhead and platen,
when measured at the right end of the platen.
Turning the adjusting cam to the RIGHT will lower the right side of the guide rail.
This causes the printhead gap (on the right side of the platen) to increase.
Turning the adjusting cam to the LEFT will raise the right side of the guide rail. This
causes the printhead gap (on the right side of the platen) to decrease.
When the adjusting lever is set to position 3, the distance between the printhead and platen
increases. The electrical contact (attached to the carriage cover) touches a contact pad on the
spacing motor circuit board. This reduces printing speed. Slower speeds ensure adequate
printing pressure.
Refer to Section 3.3 ( ) for further details on the Printhead Gap Adjustment.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
NOTE: The ribbon drive gear assembly is secured to the top of the spacing motor assembly by
the four claw tabs.
The ribbon drive mechanism drives the ribbon in sync with the spacing operation. The mechanism
is driven by the spacing motor.
Ribbon Cartridge
A uni-directional feed, continuous ribbon is used. The ribbon is replenished by a built-in
ink tank in the ribbon cartridge.
Ribbon Feed Operation
As the spacing motor rotates, the ribbon gear (on the spacing motor shaft) turns the drive
gear in the ribbon cartridge via the ribbon drive gear assembly. As a result, the ribbon is
moved.
In bi-directional printing, the ribbon gear rotational direction reverses each time the direction
of the carriage movement reverses. In this case, the gears in the ribbon drive gear assembly
move the position of an intermediate idler gear, causing the ribbon to feed in one direction.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
The paper feed mechanism is designed so when the stepper motor rotates 48 steps (360 degrees),
paper is fed 0.17 inch (4.23 mm).
Friction Feed
When the release lever is set to the friction feed position, the release lever disengages the change
gear from the tractor gear. At the same time, the release lever applies pressure to push the pressure
rollers against the platen, allowing paper to be fed.
Tractor Feed
When the release lever is set to the tractor feed position, the release lever allows the reset
spring to push the change gear toward the tractor gear. At the same time, the release lever
pushes the pressure rollers away from the platen, which allows paper to be fed by the push
tractor.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
When the printer runs out of paper, the paper-end lever falls into the groove of the paper chute.
The rear part of the paper-end lever deactivates the paper-end sensor. An out-of-paper condition
is detected.
Paper-end is detected when the end of the remaining paper is about 1 inch (25.4 mm) from the
printhead position.
When the printer runs out of paper, the tip of the bottom paper-end lever falls into the hole in the
bottom paper guide. The rear part of the paper-end lever activates the paper-end sensor. An
out-of-paper condition is detected.
Paper-end is detected when the end of the remaining paper is about 1 inch (25.4 mm) from the
printhead position.
When paper is removed, the paper-end lever falls into the groove of the paper chute. The rear part
of the paper-end lever deactivates the paper-end sensor. An out-of-paper condition is detected.
Paper-end is detected when the end of the remaining paper is about 1 inch (25.4 mm) from the
printhead position.
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Service Guide ML320/ML321
Chapter 2 Principles of Operation
When the paper release lever is set for friction feed paper, opening the bail arm causes the
SASF switch to close. The line feed motor feeds two inches of paper. SASF motion stops
after two inches of paper feed motion and paper-end is detected.
SASF should be used for loading tractor feed paper. Okidata recommends using SASF instead
of pressing FORM FEED. Since the paper bail is opened for SASF, there is less chance of
jamming.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Adjustments ( )
Cleaning ( )
Lubrication ( )
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
This section lists the parts replacement, adjustment, cleaning, and lubrication procedures.
Disassembly should not be performed unless absolutely necessary. NEVER perform disassembly
on a malfunctioning unit until you have followed the failure analysis procedures ( ) in Section Four
of this Service Handbook.
Follow the procedures listed in Adjustments and Service Settings. Adjustments may be required
when either consumables or parts are replaced. Failure to perform these procedures could result
in unnecessary service calls.
- Before starting disassembly and assembly, always power OFF the unit and detach the
power cord.
- Since screws, collars and other small parts are easily lost, they should be temporarily
attached to the original positions.
- When handling circuit boards use extreme care. Integrated circuits (microprocessors,
ROM, and RAM) can be destroyed by static electricity.
- Perform the Printhead Gap Adjustment (Refer to Section 3.3) when the following occur.
B
Rev B units are retrofitted to include a modified interconnect module, which prevents corrosion.
C
Rev C units have a cable harness connection between the power supply board and the main control
board. The cable harness replaces the interconnect module.
D
Rev D units have no power supply board. The circuitry for the power supply board has been
incorporated on the main control board.
The Rev A and Rev B main control board (LXMC) and power supply board (PAII) cannot be used
in Rev C units.
Rev D units do NOT use Rev A, Rev B, or Rev C main control boards, transformers, operator panels,
upper covers, and lower covers. Rev D units have a unique main control board (LXMR), no power supply
board, a 50 volt transformer, and a unique operator panel (LXON).
NOTE:
Please refer to the parts lists (Appendix B) for parts differentiation. Please be sure of the parts you
need before ordering to avoid confusion and incorrect parts orders.
Transformer
Interconnect Module
Cable
Cable Guide
Item Okidata Purpose / Function of Item A B C D
P/N
Covers
Chassis
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
General Information
This section contains the printer disassembly procedures. Only the removal procedures are explained.
Reverse the procedure for the installation.
At the bottom of each procedure is a listing of the parts covered in that procedure. The Okidata part
number, item description, applicable product, comment (RSPL, Option, Consumable), serial number
revision level, and the cross-reference(s) to Appendix B are provided for each part. Items included in
the Recommended Spare Parts List are indicated by the acronym RSPL. N/A appears where a part
number is not available.
This Service Handbook lists the disassembly procedures for major components of the unit. Okidata
does NOT recommend disassembling a unit which is operating normally. If you decide to perform
disassembly during this training, Okidata recommends that you perform only the disassembly
procedures for RSPL items. All other procedures are provided to assist you in identifying parts.
It is not likely that you will perform these procedures while servicing the product.
Be sure to read all notes, cautions, and warnings, as they contain important information regarding
assembly/disassembly.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
1) Press the AC switch (1 shows location) and power OFF the printer.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
CAUTION: To avoid damaging the ribbon protector, slide the printhead towards the center of
the printer before removing the separator assembly.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Move the printhead mounting clamp (3) in the direction of arrow A to unlock
the printhead (4).
- Lift and remove the printhead from the carriage frame (5).
NOTE: When installing the printhead, push the printhead towards the platen.
Part Item App. B
Number Description Product Comment Revision Reference
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Wrap a rubber band around the wire extensions of the interface connector.
This pulls the extensions in and avoids damage when the cover is removed. (Notshown).
- Insert a flat-blade screwdriver through the slots (2) and disengage the claws of the cover.
The Microline 320 has three slots. The Microline 321 has five slots.
- Lift the front of the upper cover assembly (3) and remove the assembly.
- The upper cover assembly contains the access cover assembly (4), the sheet separator
assembly (5), the rear cover (6), and the middle cover (7)
CAUTION: Do NOT rotate the access cover past the vertical when removing it.
The tab extensions can break.
The Rev D middle cover is NOT compatible with the Rev A, B, and C middle cover.
Before installing the cover, move the bail arm lever towards the back of the printer and move
the release lever towards the front of the printer.
After installation, verify that the cover is correctly seated in the front slots. The cover will
warp if it is incorrectly installed. Check that the paper bail moves properly.
NOTE: The operator panel assembly and board for the Rev D units are NOT compatible with
the Rev A, B, and C operator panel assembly and board.
- 3.2.01 ( )
- 3.2.04 ( )
- Release the claws (1) and remove the operator panel assembly (2) from the chassis
(3). As the operator panel assembly is removed, it must be detached from the connector
(4) on the control board (5).
- Release the eight claws (6) and remove the operator board (7) from the bezel (8).
Part Item App. B
Number Description Product Comment Revision Reference
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Rev A and B
CAUTION: Check the contacts between the power interconnect module, the control
board, and the power supply board (Rev A and B units ONLY). Clean the
contacts if dirty. If contacts are bent or broken, replace the module. Proper
inspection and cleaning of the power interconnect module contacts can eliminate
a false diagnosis of a failed control board or power supply board.
Check the contacts and connections of the control board. If good contact is not
made at all connections and ground points, false diagnosis will occur.
The sensor lever must be positioned in the paper end sensor. If the lever is not correctly
positioned, the ALARM lamp will light and the unit will not automatically load paper or
receive data.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
CAUTION: Check the contacts and connections of the control board. If good contact is
not made at all connections and ground points, false diagnosis will occur.
- Lift the locking claw (2) and pull the control board (3) away from the chassis.
- Guides (A and B)
The sensor lever must be positioned in the paper end sensor. If the lever is not correctly
positioned, the ALARM lamp will light and the unit will not automatically load paper or
receive data.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
CAUTION: Check the contacts and connections of the control board. If good contact is not
made at all connections and ground points, false diagnosis will occur.
- Lift the locking claw (2) and pull the control board (3) away from the chassis.
The sensor lever must be positioned in the paper end sensor. If the lever is not correctly
positioned, the ALARM lamp will light and the unit will not automatically load paper or
receive data.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Insert a flat-blade screwdriver at the bottom of the chassis (1) and push up on the two
claws (2) of the IC card (A) panel (3) to release the panel.
- Pull the panel in the direction of arrow A and remove the panel.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
3.2.08 Transformer
Revs A and B
NOTE: The transformer contains a built-in temperature fuse. Once the fuse opens, the transformer
MUST be replaced.
The Rev A, B, and C transformers are NOT compatible with the Rev D transformer.
The transformer shown in the diagram is the Rev A and B transformer. This unit has been
replaced by the Rev C unit, shown on the following pages.
- Remove the screw (3) and detach the grounding wire (4).
- Push the lock spring (6) on the transformer and detach the lock spring from transformer
clamp A (7).
- Lift the A side of the transformer and detach it from the transformer clamp B (8).
Part Item App. B
Number Description Product Commen Revision Reference
t
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Transformer Rev C
NOTE: The transformer contains a built-in temperature fuse. Once the fuse opens, the transformer
MUST be replaced.
The Revs A, B, and C transformers are NOT compatible with the Rev D transformer.
- Remove the screw (3) and detach the grounding wire (4).
- Push the lock spring (6) on the transformer and detach the lock spring from transformer
clamp A (7).
- Lift the A side of the transformer and detach it from the transformer clamp B (8).
Part Item App. B
Number Description Product Comment Revision Reference
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Transformer Rev D
NOTE: The transformer contains a built-in temperature fuse. Once the fuse opens, the transformer
MUST be replaced.
The Revs A, B, and C transformers are NOT compatible with the Rev D transformer.
- Remove the screw (3) and detach the grounding wire (4).
- Push the lock spring (6) on the transformer and detach the lock spring from transformer
clamp A (7).
- Lift the A side of the transformer and detach it from the transformer clamp B (8).
Part Item App. B
Number Description Product Comment Revision Reference
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Working from the bottom of the chassis, push on and release the claw (1) of the filter
assembly (2).
- Lift the AC connector (3) and the AC power switch (4) from the two guides on the main
frame.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Revs A and B
NOTES: The Rev D printers do NOT have a power supply board. The control board contains
circuitry to provide the power supply function.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
NOTES: The Rev D printers do NOT have a power supply board. The control board contains
circuitry to provide the power supply function.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Revs A and B
- Use a straight-slot screwdriver to release the claws (1) from the chassis clamps (2).
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Use a straight-slot screwdriver to release the claws (1) from the chassis clamps (2).
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Use a straight-slot screwdriver to release the claws (1) from the chassis clamps (2).
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Use needle-nose pliers to remove the left bail arm spring (1).
- Release the claw (2) and detach the left bail arm (3) from the bail bar (4).
- Pull the left bail arm through the guide hole (5) in the chassis and remove the arm.
- Detach the bail bar from the right bail arm (6).
- Use needle-nose pliers to remove the right bail arm spring (7).
- Release the claw (8) and detach the right bail arm from the bail bar.
- Pull the right bail arm through the guide hole (9) in the chassis and remove the arm.
Part Item App. B
Number Description Product Commen Revision Reference
t
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
NOTE: Remove this cover to provide access when connecting the head cable to the control board.
- Release the two claws (2) and remove the head cable access cover (3).
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
CAUTION: When handling the head cable, do NOT bend the cable at sharp angles
or you may damage it.
- Insert a straight-slot screwdriver through the access slots and release the two front
claws (2) and the two rear claws (3) of the ribbon drive assembly (4).
- Detach the head cable (5), the cable clamp (not shown) and the contact pressure rubber
(6) from the drive assembly.
When lubricating, refer to Section 3.5 of this Service Handbook.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Note the position of the connector (1). During assembly, the connector's orientation is
critical for correct printhead operation.
- Remove the space motor assembly (3). Be careful not to lose the slider (4).
NOTES:
Installation
- Do not touch the contacts of the assembly.
- The contact side of the head cable faces down when the carriage cable is inserted
into the connector on the space motor assembly.
- Work the cable from side to side until it is fully seated in the connector. No contacts
should be visible.
Cleaning
Lubrication
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Use a flat-blade screwdriver to release the tabs of the ribbon protector (2).
- Remove the carriage shaft from the guide hole by pulling at position C.
Installation
- After installing the carriage shaft, check the printhead gap adjustment.
Cleaning
Lubrication
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Release the claw (2) from the hole (3) in the chassis.
Installation
Cleaning
CAUTION: Do NOT lubricate the space rack. Lubricating the space rack will attract dust. If enough
dust accumulates on the space rack, printing problems will occur.
Part Item App. B
Number Description Product Commen Revision Reference
t
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Pull the adjusting cam (1) out and rotate it to the horizontal position.
- Release the adjusting cam from the guide (2) in the chassis and remove the cam.
- Push the claw (3) in the direction of arrow A to disengage the guide rail (4) at position B.
- Pull the guide rail in the direction of arrow C to release it from the guide (5) in the chassis.
- Rotate the lock levers in the direction of arrow B. This releases the platen assembly
(3) from the chassis.
NOTES:
Installation
- Before installation, turn the bias gear (4) towards the front of the printer as far
as it will go.
- Set the platen assembly into place.
- Verify that the bias gear securely engages the line feed motor gear.
- Set the release lever to OPEN (front) and check that the groove of the paper chute
firmly engages with the groove of the main chassis.
- Check the printhead gap adjustment. Refer to Section 3.3 of this Service Handbook.
Cleaning
Lubrication
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
NOTES: Use care when performing this procedure. The plastic claws will break if too much
pressure is applied.
If the line feed motor gear breaks or becomes worn, it is not necessary to replace the entire
line feed motor assembly. The gear (6) can be replaced without removing the line feed motor
assembly. However, the platen assembly MUST be removed. The line feed idle gear should be
removed ONLY if it must be replaced. The claws will break when the gear is removed. A new
gear must be installed.
- Use a straight slot screwdriver to open the lock levers (2) and push the bracket (3) of the line
feed motor (4) in the direction of arrow A.
Installation
If the line feed motor assembly is not correctly installed, excessive wear of the platen
gears will occur.
Verify that the tabs are not bent. If the tabs are bent, straighten them. The assembly
will not seat if the tabs are bent. If the assembly is not seated correctly, the gears will
not correctly align.
Rotate the bias gear towards the front of the printer as far as the gear will turn. This
aligns the bias gear with the platen gear.
Set the platen assembly in place, securely engaging the idler gear with the platen gears.
Lock the line feed motor assembly into position. Verify that the tabs are not bent.
Part Item App. B
Number Description Product Commen Revision Reference
t
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
NOTES: If the line feed motor gear breaks or becomes worn, it is not necessary to replace the
entire line feed motor assembly. The gear can be replaced without removing the line
feed motor assembly. However, the platen assembly MUST be removed. The line feed
idle gear should be removed ONLY if it must be replaced. The claws will break when the
gear is removed. Anew gear must be installed.
- Use a small cutting pliers to cut the three claws (1) that secure the line feed motor gear
(2) to the support shaft (3).
- Lock the three claws of the gear into the groove of the shaft.
- Rotate the bias gear towards the front of the printer as far as the gear will turn. This aligns
the bias gear with the platen gear.
- Set the platen assembly in place, securely engaging the line feed motor gear with the platen
gears.
CAUTION:
If the claws do not lock into the groove of the support shaft, the gear will "walk" off the shaft
during use. Verify that the line feed motor gear and line feed motor assembly are correctly
installed. Verify that the line feed motor gear and the platen gears are correctly aligned.
Incorrect installation and alignment will cause line feed motor gear breakage and wearing.
Do NOT apply lubricant to the teeth of the line feed motor gear. Grease causes the plastic
to break down, resulting in premature wear of the gear teeth.
NOTE: Use care when performing this procedure. The plastic extension will break if too much
pressure is applied.
- Insert a straight-slot screwdriver between the line feed motor interconnect module (1) and
the chassis. Then, carefully pry the module from the two guide holes (2).
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
CAUTION: - Please read through this entire procedure before performing it.
- Do NOT press against the vertical extension of the reset spring at any time
during this procedure.
- Firm pressure will release the reset spring, NOT brute force.
- Use a flat-blade screwdriver to press down at position A of the reset spring (1).
NOTE:
Lubrication
Parts Replacement
The Kit: Idler/Change Gear (ML300) includes the change and idler gears. Order
this kit when replacing these parts.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Release the claw (1) from the guide (2) in the chassis.
- Pull the release lever (3) in the direction of arrow A and remove the lever.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Use a straight-slot screwdriver to detach the coupling holes (1) of the support spring
(2) from the projections (3) on the main chassis. (Microline 321 ONLY)
- Work from left to right and use a straight-slot screwdriver to detach the coupling holes (4)
from the projections (5) on the chassis.
When installing the paper pressure guide, be sure to fit it into the projections (5) and guide plates
(7) at the same time.
The Microline 320 has five coupling holes and ten guide plates.
The Microline 321 has seven coupling holes and thirteen guide plates.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Turn the release link (2) as shown in View A so the spine (3) is aligned with the slot
(4) in the guide hole.
- Slide the release link off the pressure roller assembly (5).
- Remove the pressure roller assembly by sliding it through the guide hole (6).
NOTES:
Installation
Attach the paper end lever (7) to the shaft of the sensor lever (8). Refer to View B for
the correct position. If the paper end lever is incorrectly positioned, paper jams / no
paper-end indications will occur.
Position the tab of the paper chute firmly with the groove of the main frame.
Engage the cut-sheet paper end lever (attached to the bottom of the paper chute) to the
bottom paper end lever (under the main frame). Then, install the paper chute.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
NOTE: Horizontal movement of the left tractor is restricted by a stopper on the lower cover.
- Use a needle nose pliers to release the claw (1) of the tractor gear (2) from the groove
(3) in the lower tractor feed shaft (4). The lower tractor feed shaft is square.
- Lift the lower tractor feed shaft above the guide (5).
- Slide the lower tractor feed shaft in the direction of arrow B until the C side is free of the
guide hole (6).
- Lift the upper tractor feed shaft (7) above the guide (8). The upper tractor feed shaft is round.
- Raise the lock levers (10) on the left (11) and right (12) tractor assemblies.
- Remove the left tractor assembly, the sheet guide (13), and the right tractor assembly.
NOTES:
Installation
The tractors must be synchronized. The pins (14) on the left and right tractors must be aligned
when installed. Also, verify that the guide holes (15) in the tractor drive gears are facing the same
direction.
The left tractor assembly must be positioned to the left (line feed motor side) of the plastic tab
and ground plate. This limits movement and correctly positions the paper against the paper end
sensor.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
- Work the sensor lever from the guide hole (3) in the chassis and remove the lever.
Part Item App. B
Number Description Product Commen Revision Reference
t
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
NOTE: The paper end lever guide is accessed from the bottom of the printer.
- While pushing on the six claws (1), detach the sensor cover (2). Four of the six claws
are visible in the illustration.
- Lift the paper end (B) lever (3) from the chassis.
Part Item App. B
Number Description Product Commen Revision Reference
t
All disassembly procedures must be carried out to reach the main chassis assembly (1).
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
3.3 ADJUSTMENTS
General Information
This section contains the procedure for performing the adjustment on the Microline 320
and 321 printers. This procedure may be required when replacing either consumables or
parts. The disassembly / assembly procedures list the required adjustment and refer you
to this section. Failure to perform these procedures may result in unnecessary service calls.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
Before performing this adjustment, always verify that the printhead is properly installed.
The printhead gap adjustment procedure should be performed when the following occur.
6) Slide the carriage assembly to the left (line feed motor) side of the platen.
7) Use a feeler gauge to check the printhead gap. The printhead gap must measure:
8) Use a straightened paper clip to press down on the adjusting gear. This separates the gear from
the adjusting lever. Keep pressing down on the adjusting gear while performing Step 9.
10) Slide the carriage assembly to the right (platen knob) side of the platen.
11) Use a feeler gauge to check the printhead gap. The printhead gap must measure:
12) If the gap measurements are different between the left and right positions, turn the adjust cam.
Turning the adjust cam adjusts the height of the ruler guide.
Turn CLOCKWISE to increase the printhead gap. The guide rail is lowered.
13) Check the printhead gap at the left, right, and center of the platen.
14) If the printhead gap is not the same in all three positions, return to Step 6.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
3.4 CLEANING
An accumulation of paper dust is the most frequent cause of print quality problems in a dot matrix
printer. Small pieces of paper can cause paper jams. A dirty platen will smudge paper. It is
important to clean the printer regularly, paying particular attention to the printhead area and
paper paths.
If the lubrication procedures are not performed properly, the printer will require more frequent
cleaning. Excessive lubricant attracts dust and accumulations build up quickly.
Keeping the covers in place and performing the cleaning procedures correctly will help ensure
the highest quality printer output.
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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
3.5 LUBRICATION
The Lubrication Chart will direct you to use the following amounts of lubricant.
Medium
Oil: three to four drops
Grease: thin coating (approximately 0.15 inch)
Small
Oil: one drop
Grease: extremely thin coating (approximately 0.008 inch)
WARNING : Do NOT allow lubricant to contact the following areas. Poor print quality will result.
Ribbon Cartridge
Printhead
Platen Surface (Rubber Face)
Pressure Roller (Rubber Face)
Tractor Pins
Space Motor Board
Electrical Contacts and Connections
Space Rack
Carriage Drive Belt
Head Cable
Microswitches
Pressure Rollers (on Bail Bar)
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Service Guide ML320/ML321
Chapter 4 Failure & Repair Analysis
4.1.01 Introduction
This section is used to isolate problems to the assembly level. Application problems and
detection of faulty components on the printed circuit boards are not addressed.
When troubleshooting a defective unit, refer first to Section 4.4 of this Service Handbook.
This section contains tips on preventing problems as well as a list of common problems.
Next, refer to Section 4.6. Repair Analysis Procedures (RAPs) will ask you questions or
require you to make observations. The answers to these questions and the results of
your observations determine your next course of action. Use the RAP Index to identify
which RAP should be used to resolve the problem with the machine.
If you encounter a situation that is not addressed by the documentation in this kit,
please report the problem to Okidata. Send your report to the Okidata Technical
Training Group. Refer to the Service Center Reference Guide for information on
contacting Okidata.
A
Rev A units are original production units. An interconnect module connects the power supply board
to the main control board.
B
Rev B units are retrofitted to include a modified interconnect module, which prevents corrosion.
C
Rev C units have a cable harness connection between the power supply board and the main control
board. The cable harness replaces the interconnect module.
D
Rev D units have no power supply board. The circuitry for the power supply board has been
incorporated on the main control board.
Please Note the following:
The Rev C main control board (LXMC) and power supply board (SUII) are downward compatible
with Rev A and B units.
The Rev A and Rev B main control board (LXMC) and power supply board (PAII) cannot be used
in Rev C units.
Rev D units do NOT use Rev A, Rev B, or Rev C main control boards, transformers,
operator panels, upper covers, and lower covers. Rev D units have a unique main
control board (LXMR), no power supply board, a 50 volt transformer, and a unique operator
panel (LXON).
NOTE:
Please refer to the parts lists (Appendix B) for parts differentiation. Please be sure of the
parts you need before ordering to avoid confusion and incorrect parts orders.
Transformer
Interconnect Module
Cable Guide
Covers
Chassis
Does the paper being used meet the specifications for this product?
Check the contacts between the power interconnect module, the control board, and the
power supply board (Rev A and B units ONLY). Clean the contacts if dirty. If contacts are
bent or broken, replace the module. Proper inspection and cleaning of the power interconnect
module contacts can eliminate a false diagnosis of a failed control board or power supply board.
Check the contacts and connections of the control board. If good contact is not made
at all connections and ground points, false diagnosis will occur.
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Check the power cord connection to the printer and the outlet.
If a power strip is being used, make sure the strip is powered ON.
If the ALARM lamp does not go out after paper is loaded, refer to Section 4.4 ( ) of this
Service Handbook.
The printer does not print when the computer sends it data.
The printer may be deselected. Make sure that the SEL lamp is lit. If it is not, press the
SEL switch.
If the paper does jam, power OFF the printer. Carefully back the paper out of the paper path
by using the platen knob. Remove any shreds of paper from the paper path.
The printer suddenly changes to unidirectional printing. It then stops printing completely.
The MENU light is flashing.
This indicates a Printhead Overheat Condition. When the printer prints for a long period of time,
heat will build up in the printhead. When the printhead temperature reaches 100 degrees Celsius,
the printer will print unidirectionally. If the temperature reaches 110 degrees Celsius, printing
will stop until the printhead cools. Printing will resume after the printhead cools.
Perform the Printhead Gap Adjustment. Refer to Section 3.3 ( ) of this Service Handbook for
details.
Refer to RAP 03 ( ).
Files do not print the way the printer menu and front panel are set.
Before sending a file to a printer, many word processors send an initialization string. This string
contains codes that reset the printer to a default set of features. Otherwise, the printer might print
using features set for a previous job. The codes will override panel or menu settings. Check the
word processor's manual to see if the initialization string can be modified. If so, remove any codes
that interfere with the printer's settings.
The PRINT QUALITY, CHARACTER PITCH, and MODE switches do not work.
The Operator Panel Functions Item in the Printer Menu can be set to enable (FULL
OPERATION) or disable (LIMITED OPERATION) these features. If the printer is part
of a customized system or if it is used by different operators, a system manager may
be using this feature to maintain proper print settings.
To activate these switches, power OFF the printer. Press and hold the MODE switch while
powering ON the printer. Follow the normal menu procedures to set the Operator Panel
Functions Item to FULL OPERATION.
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The operator panel is used to display printer modes and error conditions. The table below
shows the operator panel display and the mode or condition it matches.
OFF ON N/A Normal Hex Dump The printer is in Hex Dump Mode.
Operation Refer to Section 4.7 ( )
OFF OFF N/A Normal Off-Line The printer will NOT receive data or
Operation print.
OFF ON Normal Menu Mode The operator may view or change the
Operation menu settings.
ON OFF N/A Operator CSF Paper Paper jam or paper end with CSF
Alarm Jam installed.
OFF BLINK N/A Operator Print The printer has received a PRINT
Alarm Suppress SUPPRESS code from the
computer.
OFF ON N/A Normal Hex Dump The printer is in Hex Dump Mode.
Operation Refer to Section 4.7( )
OFF OFF N/A Normal Off-Line The printer will NOT receive data or
Operation print.
ON OFF N/A Operator CSF Paper Paper jam or paper end with CSF
Alarm Jam installed.
OFF BLINK N/A Operator Print Suppress The printer has received a PRINT
Alarm SUPPRESS code from the
computer.
Curre ON Curre " " " " " " " " " " Paper Add paper
nt<R> nt Out
Mode CPI
Blinki ON Curre " " " " " " " " " " Printhead Normal
ng nt Temp
CPI
Blinking ON Spacing Go to
Error RAP 02 ( )
CAUTION: Check the contacts between the power interconnect module, the control board,
and the power supply board (Rev A and B units ONLY). Clean the contacts with if dirty.
If contacts are bent or broken, replace the module. Proper inspection and cleaning of the
power interconnect module contacts can eliminate a false diagnosis of a failed control
board or power supply board.
Check the contacts and connections of the control board. If good contact is not made at
all connections and ground points, false diagnosis will occur.
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Use the RAP INDEX to find the RAP associated with the printer's problem.
All of the RAPs will begin with a START Statement, followed by questions or another
type of statement.
If the RAPs do not lead you to the cause of a problem, please report this to
Okidata.
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RAP # Description
-- Troubleshooting Cautions............................................... ( )
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Check the contacts between the power interconnect module, the control board, and the power
supply board (Rev A and B units ONLY). Clean the contacts if dirty. If contacts are bent or
broken, replace the module. Proper inspection and cleaning of the power interconnect module
contacts can eliminate a false diagnosis of a failed control board or power supply board.
Control Board
Check the contacts and connections of the control board. If good contact is not made at all
connections and ground points, false diagnosis will occur.
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START
NO Go to A
YES Go to A
Check the AC fuse on the primary side of the filter assembly. Is it open?
NO Go to B
NO Go to B
Verify that the fuse holder is making proper contact with the fuse. Remove the fuse from the
holder. Gently squeeze both sides of the holder slightly towards each other. Reinsert the
fuse. Is the problem resolved?
+ 5 vdc
Take the voltage reading between Pin 5 and Pin 9 of CN2 on the power
supply board.
+ 38 vdc
Take the voltage reading between Pin 1 and Pin 5 of CN2 on the power supply
board. Meter should read + 40 vdc.
NO Go to C
NO Go to C
NO Go to D
NO Go to D
Are the control board contacts and the power supply board contacts properly made?
NO Go to E
YES Go to E
Replace the connector between the power supply board and the control board.
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START
NO Go to A
YES Go to A
Check the AC fuse on the primary side of the filter assembly. Is it open?
NO Go to B
NO Go to B
Verify that the fuse holder is making proper contact with the fuse. Remove the fuse from
the holder. Gently squeeze both sides of the holder slightly towards each other. Reinsert
the fuse. Is the problem resolved?
+ 5 vdc
Take the voltage reading between Pin 16 and Pin 34 of the
IC4 (ROM) on the control board.
+ 50 vdc
Take the voltage reading between both leads of C33 on the
control board. Meter should read + 50 vdc.
YES Replace the control board.
NO Go to C
NO Go to C
NO Go to D
NO Go to D
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START
Does the assembly vibrate back and forth in the same location or does it move sharply to the left
or right end of the carriage shaft?
NO Clean the contacts between the carriage cable and the space motor contacts.
NO Go to B.
YES Clean the teeth of the space motor and the space rack.
NO Go to C
NO Go to C
+ 5 vdc
Take the voltage reading between Pin 5 and Pin 9 of CN2 on the power
supply board.
+ 40 vdc
Take the voltage reading between Pin 1 and Pin 5 of CN2 on the power supply
board.
NO Go to D
NO Go to D
Are the power supply board and the control board connected properly?
NO Reseat the power supply board, the control board, and the connection between
the two boards.
NO Go to E.
Is the carriage cable properly inserted into CN2 of the control board?
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START
Does the assembly vibrate back and forth in the same location or does it move sharply to the
left or right end of the carriage shaft?
NO Clean the contacts between the carriage cable and the space motor contacts.
NO Go to B.
YES Clean the teeth of the space motor and the space rack. Make sure that the space
rack is correctly installed.
NO Go to C
NO Go to C
+ 50 vdc
Take the voltage reading between both leads of C33 on the control board. Meter should
read + 50 vdc.
YES Go to D
NO Go to D.
NO Go to D.
Is the carriage cable properly inserted into CN2 of the control board?
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START
Is the head cable correctly inserted into CN2 of the control board?
NO Go to A.
Are the contacts between the space motor and the carriage cable properly made?
NOTE:
1. Is the head gap correctly set for the type of paper being used?
2. Remove the printhead. Examine the pins. Do they appear damaged? If so, replace
the printhead.
START
YES Go to A.
NO Set the release lever to OPEN. Manually rotate the platen knob. Does it rotate
smoothly?
NO Go to A.
YES Check the following in the order given below. Check the operation of the platen
knob before moving between steps.
NO Go to A.
Are the connection plate and the line feed motor making correct contact?
YES Is the connection plate making correct contact with the control board?
YES Replace the control board.
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START
Is the operator panel board correctly connected to CN1 of the control board?
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START
NO Press the SELECT button to place the printer in Select Mode. The SELECT
lamp will be lit when the printer is in Select Mode.
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NOTE:
Before performing the procedures of this RAP, make sure that the correct protocols are
selected. Print the Menu to check protocol settings. For information on printing the Menu,
refer to Section 4.10 of this Service Handbook.
START
Is the serial interface cable correctly connected to both the serial interface board and the
host computer?
YES Replace the serial interface cable with a cable proven to work. Is the problem
resolved?
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Hexadecimal dump mode allows you to check the data sent from the computer to the printer.
All data sent to the printer, including test and printer commands, will print in both hexadecimal
and ASCII format. In the ASCII format, all non-printable codes will be represented by a period.
4.7.02 Procedure
4.7.03 Sample
In hexadecimal dump mode, the BASIC code line would print as follows.
1B 30 1E 54 68 69 73 20 69 73 20 61 6E 20 65 78 .0.
61 6D 70 6C 65 20 6F 66 20 61 20 68 65 78 61 64
65 63 69 6D 61 6C 20 64 75 6D 70 2E 0D 0A
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Interconnect Diagram
Rev A and B ................ ( )
Rev C ......................... ( )
Rev D ......................... ( )
Printhead
Rev A, B, C, and D ....... ( )
Space Motor
Rev A, B, C, and D ....... ( )
Control Board
Rev A, B, C, D ........... ( )
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4.8.03 Printhead
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Chapter 4 Failure & Repair Analysis
There are three tests which can be run for the unit.
The Rolling ASCII Print and Font Sample Tests are used to determine if the printer is operating
properly. The Serial Interface Loopback Test is used to test proper operation of the Serial Interface
Board.
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General Information
The Rolling ASCII Print Test produces a continuous printout of all 96 ASCII characters in a
rolling pattern. The type style set in the printer menu will be utilized.
At the top of the printout, you will see the Printer Model, Emulation, Country Code,
and Firmware Revision Level.
CAUTION: If 13.6 inch Paper Width is selected in the menu, and you run this test with 8.5 inch
wide paper loaded, the test will print on the platen. This may damage the platen, ribbon, and
printhead. Set the paper width to 8.5 inches before running this test.
Procedure
Verify that the printer is loaded with paper and that the paper is the correct width.
Press and hold the TOF/QUIET switch while powering ON the printer. If the printer is
powered on and the Rolling ASCII Test does not start, you may have released the
PARK/QUIET switch too soon.
To stop the Rolling ASCII Test, press the SELECT switch or power OFF the printer.
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General Information
LQ - ROMAN 10 cpi
LQ - SWISS 10 cpi
LQ - ORATOR 10 cpi
LQ - 12 cpi
HSD - 15 cpi
LQ - SWISS Proportional
LQ - ROMAN Proportional
LQ - COURIER Proportional
At the top of the printout, you will see the Printer Model, Emulation, Country Code, Interface, and
Firmware Revision Level.
CAUTION: If 13.6 inch Paper Width is selected in the menu, and you run this test with 8.5 inch wide
paper loaded, the test will print on the platen. This may damage the platen, ribbon, and printhead. Set
the paper width to 8.5 inches before running this test.
Procedure
Press and hold the LINE FEED switch while powering ON the printer. If the font sample test does
not print after you power ON the printer, you may have released the LINE FEED switch too soon.
This is a one page test. The printer will stop after printing the page. If you want to stop the
test before the page is complete, press the SELECT switch or power OFF the printer.
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NOTE: Attach a serial loopback test connector to the printer's serial port to run this test.
General Information
The Serial Interface Loopback Test checks the operation of the serial interface board.
Procedure
Verify that the ribbon and paper are installed.
Press MODE. The SEL light will go out and the MENU lamp will light.
When the MENU lamp is lit, the functions printed BELOW the operator panel
switches are activated.
Press GROUP until you access the desired group (Serial Interface). Each time you press
GROUP, the printer will print the current group.
Press ITEM until you access the desired item (Diagnostic Test).
Press MODE to record the changes and return to Print Mode. The MENU lamp will go out
and the SEL lamp will light.
I/F Good
The test runs until the SELECT switch is pressed or the printer is powered OFF.
Press and hold the MODE switch while powering ON the printer. The printer will be in Menu
Mode.
Press GROUP until you access the desired group (Serial Interface). Each time you press GROUP,
the printer will print the current group.
Press ITEM until you access the desired item (Diagnostic Test).
Press MODE to record the changes and return to Print Mode. The MENU lamp will go out and the
SEL lamp will light.
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The end user can customize printer features by changing menu settings. These settings are
automatically activated when the printer is powered ON.
Selections made in Menu Mode are stored in the printer's permanent memory. They will stay
in effect, even when the printer is powered OFF. However, they can be changed through
software commands, the front panel, and by resetting the menu. Changes made by software
commands or the front panel are canceled when the printer is powered OFF.
In the Printer Menu, the sixth item in the General Control Group is Operator Panel
functions. The settings for this item are Full Operation and Limited Operation. A system
manager may use this feature to maintain proper print settings if the printer is part of
a customized system or if it is used by different operators.
When the Printer Menu is set to Limited Operation, the PRINT QUALITY, CHARACTER
PITCH, and MODE switches of the operator panel do not work.
Follow the normal menu procedures to set the Operator Panel Functions Item
to FULL OPERATION.
Press MODE. The SEL light will go out and the MENU lamp will light.
Press MODE. The SEL light will go out and the MENU lamp will light.
When the MENU lamp is lit, the functions printed BELOW the operator panel switches
are activated.
Press SET until you access the desired setting for an item.
Press MODE to record the changes and return to Print Mode. The MENU lamp will go out and
the SEL lamp will light.
CAUTION: Always print the menu before resetting to factory defaults. All customized information
will be lost once the menu has been reset.
Menu
Press and hold the MODE and SELECT switches while powering ON the printer.
Press and hold the PARK and TOF/QUIET switches while powering ON the printer.
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Top of Form sets the print start position for the printer. It is adjustable in increments of 1/144
of an inch. The amount of adjustment is limited to avoid paper jams.
4.11.02 Procedure
Press SEL until the SEL lamp goes out. The printer is deselected.
Press and hold TOF/Quiet. While doing this, press either of the switches listed below.
The lower red line on the ribbon protector shows the baseline of the current printing
position. Use this when positioning the Top of Form.
The Top of Form is automatically saved in the printer's static memory. Powering OFF the unit
will NOT change the Top of Form. You must reset the Top of Form to change it.
NOTE: The bail must hold the paper in place. If the top of the page is set below the bail, the paper
will catch on the bail and a paper jam will occur.
Press SEL until the SEL lamp goes out. The printer is deselected.
The lower red line on the ribbon protector shows the baseline of the current printing
position. Use this when positioning the Top of Form.
Press TOF/Quiet to "save" the Top of Form as the temporary setting. It is saved in the printer's dynamic
memory. Powering OFF the unit will erase the temporary Top of Form.
NOTE: The bail must hold the paper in place. If the top of the page is set below the bail, the
paper will catch on the bail and a paper jam will occur.
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Paper Park allows single sheet paper to be printed without removing continuous feed paper
from the printer.
4.12.02 Procedure
Press PARK. The continuous feed paper will retract from the paper path. The ALARM lamp
will light and the SEL lamp will go out.
Move the paper lever to the Single Sheet Setting. This is towards the back of the printer.
Push the guide wire back into its locked position on the paper separator.
Set a sheet of paper on the separator and adjust the guides. The guides should barely touch
the edges of the paper. Be sure to position the left edge of the paper even with the reference
mark on the separator.
Print.
Set the paper lever to continuous feed. This is towards the front of the printer.
This feature allows a printed page (rear feed, continuous form) to be torn off without wasting
paper or adjusting the printer.
Forms Tear Off advances the paper from the initial printing position to the tear off position.
The top of the page (perforation) will be even with the tear bar. The tear bar is located under
the clear top of the access cover.
Paper will remain in the tear off position until the printer receives data. Then, the paper is
retracted to the initial print position.
When printing stops, the paper will advance to the tear off position.
NOTE: If the software package being used "pauses" while sending data to the printer, Forms Tear
Off may be activated (if it is enabled through the Menu). The pause must be for two or more seconds.
No data is lost. Uneven print registration will occur due to the paper movement. If the problem occurs,
deactivate Forms Tear Off through the Menu.
4.13.02 Procedure
Press MODE. The SEL light will go out and the MENU lamp will light.
When the MENU lamp is lit, the functions printed BELOW the operator panel switches
are activated.
Press MODE to record the changes and return to Print Mode. The MENU lamp will go out and
the SEL lamp will light.
Press SEL until the SEL lamp goes out. The printer is deselected.
Press and hold TOF/Quiet. While doing this, press either of the switches listed below.
The lower red line on the ribbon protector shows the baseline of the current printing position.
Use this when positioning the Top of Form.
The Top of Form is automatically saved in the printer's static memory. Powering OFF the unit
will NOT change the Top of Form. You must reset the Top of Form to change it.
Release TOF/Quiet. The paper advances from the initial print position to the tear off position.
Press SEL until the SEL lamp goes out. The printer is deselected.
Press and hold TOF/Quiet. The paper will retract to the initial print position.
Release TOF/Quiet. The paper will advance to the forms tear off position.
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Service Guide ML320/ML321
Chapter A Reference Charts
This section describes the characteristics of the printed circuit boards used in the Microline 320
and Microline 321 printers. The following areas are covered in each section.
- Function
- Firmware
- Fuses
- Jumpers
- Switches
- Sensors
- Test Points
A
Rev A units are original production units. An interconnect module connects the power supply board
to the main control board.
B
Rev B units are retrofitted to include a modified interconnect module, which prevents corrosion.
C
Rev C units have a cable harness connection between the power supply board and the main control
board. The cable harness replaces the interconnect module.
D
Rev D units have no power supply board. The circuitry for the power supply board has been
incorporated on the main control board.
The Rev A and Rev B main control board (LXMC) and power supply board (PAII) cannot be used
in Rev C units.
Rev D units do NOT use Rev A, Rev B, or Rev C main control boards, transformers, operator panels,
upper covers, and lower covers. Rev D units have a unique main control board (LXMR), no power supply
board, a 50 volt transformer, and a unique operator panel (LXON).
NOTE:
Please refer to the parts lists (Appendix B) for parts differentiation. Please be sure of the parts you
need before ordering to avoid confusion and incorrect parts orders.
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Service Guide ML320/ML321
Chapter A Reference Charts
Rev A and B
Rev C
Rev D
Function
The control board contains the microprocessor and its peripheral circuits. The drive circuits,
paper end sensor, and the interface connector are on this board. A 3.25 V lithium battery is
on this board.
Firmware
Fuses
Rev 1 and 2
Rev 3 and up
Jumpers
Sensors
Paper End
Switches
SASF
Test Points
CN6
+ 5 vdc, + 8 vdc, + 38 vdc, 10 vac
ALM-P If this line goes high (+ 5 vdc), the fuse on the filter assembly will open.
Refer to Section Two of this Service Handbook for more details.
Notes
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
The control board contains the microprocessor and its peripheral circuits. The drive circuits,
paper end sensor, and the interface connector are on this board. A 3.25 V lithium battery is
on this board.
Firmware
Fuses
Jumpers
Sensors
Paper End
Switches
SASF
Test Points
CN6
ALM-P If this line goes high (+ 5 vdc), the fuse on the filter assembly will open.
Notes
The LXMC-3 Board has gone through a modification. The older version of the board accepted
a 28 pin EPROM at the Q13 socket location. The newer version of the board accepts a 32 pin
masked ROM. It will also accept the 28 pin EPROM. No jumper changes are necessary. If a
28 pin EPROM is installed on the 32 pin Q13 socket, the four unused pins will be located
at the top.
Function
The control board contains the microprocessor and its peripheral circuits. The drive circuits,
paper end sensor, and the interface connector are on this board. It also contains the components
needed for regulating DC voltage and those needed to convert AC voltage to DC voltage.
Firmware
NONE
Fuses
Jumpers
NONE
Sensors
Paper End
Switches
NONE
Test Points
NONE
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
This board converts and regulates the AC voltage input to DC voltage and supplies the
DC voltage to the control board.
Firmware
NONE
Fuses
F1 2.0 amp / 250 VAC
Jumpers
NONE
Sensors
NONE
Switches
NONE
Test Points
CN2: Pin 1 + 40 vdc
CN2: Pin 6 + 5 vdc
CN2: Pin 10 + 8 vdc
Notes
CN1 connection from Transformer
CN2 connection to Power Interconnect Module
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
This board converts and regulates the AC voltage input to DC voltage and supplies the DC voltage
to the control board.
Firmware
NONE
Fuses
F1 2.0 amp / 250 VAC
Jumpers
NONE
Sensors
NONE
Switches
NONE
Test Points
CN2: Pin 1 + 40 vdc
CN2: Pin 6 + 5 vdc
CN2: Pin 8 + 8 vdc
Notes
CN1 connection from Transformer
CN2 connection to Power Interconnect Module
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
This assembly is a protective feature. It also filters out unwanted line noise. Its fuse will open
when a fault occurs in the printhead drive circuit, the space motor drive circuit, or any of their
peripheral circuits. This prevents component failure.
Firmware
NONE
Fuses
F2 (also known as the AC fuse)
1.5 amp (120 V)
or
Jumpers
NONE
Sensors
NONE
Switches
NONE
Test Points
NONE
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
The operator panel is the interface between the operator and the printer.
Firmware
NONE
Fuses
NONE
Jumpers
NONE
Sensors
NONE
Switches
SW1 SEL SW5 PARK / Set
SW2 MODE SW6 TOF/QUIET / Print
SW3 LF / Group SW7 PRINT QUALITY
SW4 FF / Item SW8 CHARACTER PITCH
Displays
D1 SELECT D9 NLQ
D2 ALARM D10 10 cpi
D3 POWER D11 20 cpi
D4 Not used D12 UTL
D5 Not used D13 12 cpi
D6 MENU D14 PROP
D7 TOF / QUIET D15 17 cpi
D8 HSD
Test Points
NONE
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
The operator panel is the interface between the operator and the printer.
Firmware
NONE
Fuses
NONE
Jumpers
NONE
Sensors
NONE
Switches
SW1 SEL SW5 PARK / Set
SW2 MODE SW6 TOF/QUIET / Print
SW3 LF / Group SW7 PRINT QUALITY
SW4 FF / Item SW8 CHARACTER PITCH
D1 SELECT D9 20 cpi
D2 POWER D10 HSD
D3 ALARM D11 NLQ
D4 MENU D12 12 cpi
D5 Not used D13 PROP
D6 SSD D14 Not used
D7 UTL D15 Not used
D8 10 cpi D16 17 cpi
Test Points
NONE
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Service Guide ML320/ML321
Chapter A Reference Charts
Function
This board permits the serial transport of data to and from the printer.
Firmware
ROM
Version 1Q8: 1 megabyte ROM. Contains the serial interface control program.
Version 2: None
RAM
Versions 1 and 28 kilobytes, Static. Is the Message Buffer
Processor
Version 1Q3M80C31F
Version 2Q3M80C51F
Fuses
NONE
Jumpers
Version 1SP1 Side AQ8 has ROM installed
Version 2SP1 Side BCPU Masked ROM is utilized
Sensors
NONE
Switches
NONE
Test Points
NONE
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Page: 128
Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
This appendix will assist you in identifying the assemblies and parts of the printers. Once you have
used Section Four (Failure Analysis) to find a defective part, you can locate the part number in this
section. This appendix is cross-referenced to Section Three (Maintenance) to assist you in servicing
the printers.
The format for this appendix is a series of tables with diagrams. The table contains the item reference
number, the Okidata and Oki-Japan (Oki-J) part numbers, the part description, a comments section,
and the disassembly procedure. Items with the comment RSPL (Recommended Spare Parts List),
Consumable, or Option are available from Okidata. Items without these comments are usually not
stocked. Also note that some items are only available as assemblies. Every effort has been made to
clearly indicate which items are in assemblies and which are not.
Please read the Definition of Terms in the following section carefully. It is important that you understand
the different types of classifications and their availability.
Please refer to either of the following resources for current part numbers and pricing.
Okidata's Bulletin Board (Okilink II) contains current part numbers, prices, and recommended stocking
levels for each item listed as a recommended spare part. For instructions on accessing Okilink II, refer
to the Service Center Reference Guide.
Okidata's Faxable Facts is an automated fax document retrieval system. Part numbers and pricing are
available through Faxable Facts. For instructions on accessing Faxable Facts, refer to the Service Center
Reference Guide.
REMEMBER
Current part numbers, recommended stocking levels, and pricing information are available through
Okilink II and Faxable Facts. Refer to the Service Center Reference Guide for information on
accessing these resources.
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
RSPL
Okidata recommends that this part/assembly be on hand for servicing.
Consumable
A consumable is a supply item which has a specified life and needs to be replaced
periodically. It is purchased and installed by the end user. Okidata machines are designed
to work exclusively with Okidata consumables. By using genuine Okidata consumable
products, the investment made in the equipment will be protected.
Option
An option is a part/assembly which is added to a printer. The option expands the printer's
functionality. An option may or may not be installed by the end-user. Instructions for installation
accompany each option.
Option RSPL
Okidata recommends that this part/assembly be on hand for servicing installed options.
Document
A document is a printed item which supports the service and marketing of a product.
Various documents are available from Okidata.
Blank
Okidata does not recommend stocking this item. This item should be purchased on an As
Required Basis only. The availability of this item is not guaranteed by Okidata.
320
This part is found ONLY in the Microline 320 printer.
321
This part is found ONLY in the Microline 321 printer.
Both
This part is found in both the Microline 320 and 321 printers.
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
Description Section
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
Page: 134
Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
Page: 135
Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
Page: 136
Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
Page: 137
Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
Page: 138
Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
71 50107426 Operao
tr Panel Both RSPL 3.2.05( D
3PA4025-2821 (Assembly) SSD )
G26
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
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Service Guide ML320/ML321
Chapter B Illustrated Parts Listing
113 59231001 CSF 3000 Cut Sheet Both Document N/A ABCD
N/A Feeder Maintenance
Manual
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Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)