SHARP DP-750 Service Manual
SERVICE MANUAL
Serial Dot Matrix
Printer
MODEL DP-750
CONTENTS
CHAPTER 1. Printer Handling and Maintenance.............................................1
CHAPTER 2. Specifications and Operation Principles.....................................2
CHAPTER 3. Disassembly and Assembly .....................................................10
CHAPTER 4. Troubleshooting........................................................................29
PARTS GUIDE (PRINTER ASSEMBLY : KI-OB2014RC01)
APPLICATION MODEL : UP-600 ("U" & "A" version)
Parts marked with " " are important for maintaining the safety of the set. Be sure to replace these parts with specified
ones for maintaining the safety and performance of the set.
This document has been published to be used
SHARP CORPORATION
for after sales service only.
The contents are subject to change without notice.
Symbol/PartsCod)
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INTRODUCTION
This manual explains the operation principles and servicing procedures for the Citizen dot matrix printer DP750 series. It is written for personnel
servicing these printers in the field.
FEATURES
The DP750 series printer are a station printers providing 45 mm x 2 line print capability. Developed for POS/ECR applications, the printers offer the
following features.
• The High-performance 9-pin print head with a print speed of approx 3.0 lines per second ensures high-quality printouts.
• Clamshell design (opening and closing mechanism for the paper feed section) makes paper loading easy and facilitates easier maintenance.
• Pull-type paper transport reduces risk of paper jams.
• Versatile array of options:
Take-up device, paper feed device, validation sensor, receipt/journal near-end sensor.
CONTENTS
CHAPTER 1. Printer Handling and Maintenance ..........1
CHAPTER 2. Specificatio ns and Ope ratio n Princip les ....2
2-1 General Specifications .............................................2
2-2 Mechanism Outline ...................................................4
2-3 Mechanism and Operation Principles .....................4
2-3-1 Drive Force Transmission Assembly ...................4
2-3-2 Sensor Assembly .................................................4
2-3-3 Print Head Assembly ............ .............. .. .. .. ...........5
2-3-4 Paper Feed Assembly .........................................6
2-3-5 Ribbon Cassette Assembly .................. .. .. .. .. .. .....6
2-3-6 Paper Take-up Assembly ....................................7
2-4 Connectors ................................................................8
CHAPTER 3. Disassembly and Assembly ...................10
3-1 Required Tools .......................................................10
3-2 Disassembly Procedure .........................................10
3-3 Assembly Procedure ..............................................10
3-4 Adjustment ..............................................................23
3-4-1 Print Speed Adjustment .....................................23
3-4-2 Platen/Head Gap Adjustment ............................24
3-4-3 Bi-directional Printing Shift Adjustment .............24
3-4-4 RP/HP Waveform Check ...................................25
3-5 Head Assembly Replacement ...............................26
3-5-1 Disassembly Procedure ....................................26
3-5-2 Assembly Procedure .........................................27
2-4-1 Terminal Layout .................... .. .......................... ...8
2-4-2 Terminal Functions ......... .. .. .............. .. .............. .. .8
2-4-3 Terminal Circuit Diagram .....................................9
CHAPTER 4. Troubleshooting ........................................29
4-1 Repair Procedure ...................................................29
4-2 Repair Steps ...........................................................29
CHAPTER 1. Printer Handling and Maintenance
(1) If printer paper other than the recommended
paper is used, print quality and service life
cannot be guaranteed.
Make sure that the paper width and quality
are within specifications.
(2) Protect the head surface from mechanical
shocks and from foreign objects.
(3) Remove any contamination from the print
head surface by lightly wiping with a cotton
swab moistened with ethanol or similar product.
(4) During transport and during extended
periods of non-use, remove the ribbon
cartridge.
(5) If the print head is powered while
condensation is present, the head may be
destroyed.
Make sure that any condensation has been
fully dried before starting to print.
(6) Loading paper
Cut the tip of the paper in a straight line and
make sure that the paper is not frayed, folded,
or creased.
When the paper emerges from above the
print head, grasp it and pull it out slightly, to
verify that it is set straight.
(7) Removing paper
Remove the paper only after printer operation
has ceased.
Pull the paper straight out in the same direction
which it emerges from the printer.
o: correct
u : incorrect
1
CHAPTER 2 . Specifications and Operation Principles
2-1 General Specifications
Printing method
Printing direction
Printing speed
Print format
Paper feed
Print head
Detection
functions
Paper feed
solenoid
Print solenoid
Total number of dots
Basic character configuration
Basic number of columns
Character dimensions
Column spacing
Paper feed principle
Paper feed pitch
Fast-forward speed
Inking
Number of wires
Wire diameter
Wire pitch
Dot pulse
Reset pulse
Home position
Validation
Near end
Drive voltage
Resistance
Drive voltage
Resistance
Rating
Serial impact dot matrix printer
Bi-directional printing
Approx. 3.0 lines/second m10%
Receipt side: 108 dots/216 positions
Journal side: 108 dots/216 positions
Validation: 248 dots/495 positions
7 x 7 or 7 x 9 (half-dot)
Receipt: 24
Journal: 24
Validation: 55 (1line)
1.36 (W) x 2.4 (H) mm (7 x 7 dots)
1.36 (W) x 3.1 (H) mm (7 x 9 dots)
1.59 mm
Friction feed, separate for receipt and journal
4.23 mm m10% (1/6 inch)
Approx. 30.0 lines/second
Dedicated ribbon cartridge (monochrome: purple)
9
Ø 0.3 mm
H: 0.176 mm, V: 0.353 mm
Photo interruptor
Photo interruptor
Photo interruptor
Photo interruptor
Micro switch
24.0 V DC m10%
˚C
34 ohms m10% (at 25
)
24.0 V DC m10%
˚C
8.25 ohms m10% (at 25
)
RemarksItem
24.0 V DC, 25˚C, continuous printing
Character spacing: 2 positions
Option
Motor
Type
Drive voltage
Peak current
Average current
DC brush motor
24.0 V DC m10%
Approx. 1.6 A
Approx. 250 mA
2
At startup with 24.0 V DC, 25˚C
During continuous
printing with 24.0 V DC,
25˚C
Rating
Printer paper Width: 44.5 0.5 mm, outer diameter: max. Ø 83 mm
Take-up device
Connection principle
Service life
Ambient
conditions
Dimensions
Roll paper
Validation paper
Mechanism
Head
Operation
environment
Storage
environment
135 - 210 mm (W) x min. 70 mm (H) Single-line validation
Built-in
Pin connector
MCBF 4 million lines, maximum 8 million lines
100 million characters (2 million dots/pin)
Temperature: 0 to 50˚C
Humidity: 10-90% RH, above 39˚C equivalent to 40˚C 85% RH
Temperature: -25 to +70˚C
Humidity: 40˚C 90% RH, 96 hours
150 (W) x 230.3 (D) x 150.7 (H) mm (Type A)
150 (W) x 234.6 (D) x 123.7 (H) mm (Type B)
RemarksItem
No condensation
To be stored with ribbon
cartridge removed
Including take-up
device
Weight
Approx. 1180 g
3
)
2-2 Mechanism Outline
g
The mechanism of this printer can be divided
into 9 blocks.
• Drive force transmission assembly
• Sensor assembly
• Print head assembly
• Paper feed assembly
• Ribbon cassette assembly
• Paper take-up assembly
• Frame
• Motor assembly
For information on peripheral circuitry
connected to this printer, please refer to the
respective documentation.
2-3 Mechanism and Operation
Principles
This section explains the construction and
operation of 8 out of the 10 blocks listed above
(excluding the frame and motor assembly).
2-3-1 Drive Force Transmission Assembly
The drive force of the motor assembly is
transmitted to the various parts as follows. Print
head via bevel gear, Paper feed, via PF gear,
Ribbon cassette via worm wheel, Paper take-up
assembly via winder pulley.
2-3-2 Sensor Assembly
The sensor assembly is comprised of 3 sensors;
the dot pulse sensor (DP), home position sensor
(HP) and reset pulse sensor (RP).
(1) Dot pulse sensor/home position sensor
Main PCB assembly
Home position sensor (HP)
Dot pulse sensor (DP
Motor assembly
(2) Reset pulse sensor
Worm wheel
Motor assembly
Idling gear 2
Idling gear 1
Bevel gear 1
Bevel gear 2
Motor gear
Reduction gear 1
PF gear
Reduction
gear 2
Reduction
gear 4
Reduction
ear 3
Winder
pulley
Reset pulse sensor (RP)
Main PCB assembly
Head assembly
Carriage
4
g
(2) Head drive assembly
Head assembly
Carriage drive pulley
Timing belt assembly
Carriage drive pulley
Carriage
2-3-3 Print Head Assembly
(1) Print control
Printing is carried out by the print head
comprising of 9 solenoids and moving from left
to right. The print timing is controlled by the
home position sensor (HP), dot pulse sensor
(DP), and reset pulse sensor (RP).
Print head
Powered
Powered
Powered
Powered
Powered
Powered
Powered
Powered
Powered
HP
DP
Print solenoid #1
Print solenoid #2
Print solenoid #3
Print solenoid #4
Print solenoid #5
Print solenoid #6
Print solenoid #7
Print solenoid #8
Print solenoid #9
Home position sensor
Dot pulse sensor
Carriage drive gear
ear 1
Bevel
(3) Print head drive assembly
Wire spring
Print wire
Armature
Solenoid assembly
Bevel gear 2
Armature stopper
Armature springNose assembly
RP
Reset pulse sensor
5
2-3-4 Paper Feed Assembly
g
(1) Paper feed mechanism
2-3-5 Ribbon Cassette Assembly
(1) Ribbon cassette feed mechanism
Pressure rollers
Idling gear 2
PF gear
PF roller
assembly
PF latches
PF armature
PF solenoid
assembly
Ribbon cassette
Ribbon drive shaft
Ribbon drive gear
Worm wheel
Reduction
ear 1
6
2-3-6 Paper Take-up Assembly
(1) Paper take-up mechanism
Spool
Winder timing belt
Idle gear 2
(3) Take-up mechanism types
Spool gear
Type which is the same height as the main unit
Spool holder assembly
(2) Near-end detection mechanism
Roll paper
Roll paper core
hole center
(when diameter is large)
Winder pulleys
Type which is lower than the height of the main unit
Microswitch
Roll paper core
hole center
(when diameter is small)
End switch leverSwitch holder
7
2-4 Connectors
2-4-2 Terminal Functions
2-4-1 Terminal Layout
Connector type
Printer side: Molex 5342-30T2
Host side: Molex 5320-30AT2
Pin arrangement diagram
29
30
Pin
no.
1
2
3
1
4
5
2
6
7
8
9
10
11
12
13
14
Terminal name Function
Print solenoid #3
Motor (-) VM COM.
VM COM.
Print solenoid #7
Motor on/off signal
Print solenoid COM.
Home position sensor output
Print solenoid COM.
VS
VS
Dot pulse sensor output
Print solenoid #5
Motor (+)
+VM (+24 V)
Print solenoid #2
—
Print solenoid #1
—
Multi-line validation
SOL. (option)
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Print solenoid #9
—
Print solenoid COM.
—
Print solenoid #8
Paper feed solenoid (J)
Print solenoid #4
Paper feed solenoid (R)
Print solenoid COM.
GND
Print solenoid #6
Reset pulse sensor output
—
—
+5 V
VS
VS
30
—
8
2-4-3 Terminal Circuit Diagram
Print solenoid #3
Motor (-) 24 V GND
Print solenoid #7
Motor ON/OFF signal
Print solenoid COM. (VS)
H.P. (home position pulse)
Print solenoid COM. (VS)
D.P. (dot pulse)
Print solenoid #5
Motor (+) (+24 V)
Print solenoid #2
(reserved)
Print solenoid #1
(reserved)
Print solenoid #9
(reserved)
Print solenoid COM. (VS)
Blank
Print solenoid #8
Paper feed solenoid (J)
Print solenoid #4
Paper feed solenoid (R)
Print solenoid COM. (VS)
GND
Print solenoid #6
RP (reset pulse)
Blank
Blank (RP)
+5 V
Blank
9
CHAPTER 3. Disassembly and Assembly
Please observe the following precautions when
performing maintenance.
Note
(1) If the unit is working properly, do not
disassemble, reassemble, or adjust it
unnecessarily. The adjustment screws in
particular should not be loosened needlessly.
(2) After servicing, double-check that the unit
has been assembled correctly before turning
the power on.
(3) Never attempt to print when printer paper is
not loaded.
(4) Verify that the printer paper is loaded
correctly.
(5) When servicing the unit, take care not to
leave any screws or other loose parts in the
unit.
(6) When disassembling and reassembling the
unit, take care not to place strain on any
connecting wires, and check that the wires
are not damaged or routed incorrectly.
(1) Screw nuts on fastening screws (M3x10 hex socket
screws) and insert screws into paper guide (U). Make
sure that nuts fit snugly into V-shaped cutouts on
paper guide (U).
Fastening screw
Nut
Rear
V-shaped cutout
Paper guides (U)
3-1 Required Tools
1. Phillips screwdriver 8. Tester
2. Flatblade screwdriver 9. Oscilloscope
3. Pincette 10. Thickness gauge
4. Mini radio pliers (0.5 mm)
5. Oil brush 11. Dial tension gauge
6. Mini nipper (30 - 50 gf)
7. Hex wrench
(nominal 2.5)
3-2 Disassembly Procedure
Remove the parts from the frame in the opposite
order from the steps described in "3-3 Assembly
Procedure".
3-3 Assembly Procedure
The description of the assembly procedure
assumes that the individual assemblies are
complete. For information on the procedures for
individual assemblies, please refer to "Section 5
Parts List". The part names used in the
explanatory text are those indicated in Section 5
“Parts Lists”. These part names are used
commonly throughout this service manual.
(2) Fit pressure roller springs (L) and (R) onto both sides
of PF housing and set platen assembly in place.
Rear
Pressure roller
spring (L)
Platen assembly
Pressure roller
spring (R)
PF housing
10
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