Star Micronics NX-1000 series, LC-10 series Technical Manual
DOT MATRIX PRINTER
NX-1000SERIES
LC-10SERIES
TECHNICAL MANUAL
[ NINTH EDITION ]
NOTICE
• All rights reserved. Reproduction of any part of this manual
in any form whatsoever, without STAR’s express permission is forbidden.
• The contents of this manual are subject to change without
notice.
• All efforts have been made to ensure the accuracy of the
contents of this manual at the time of going to press.
However, should any errors be detected, STAR would
greatly appreciate being informed of them.
• The above notwithstanding, STAR can assume no respon-
sibility for any errors in this manual.
© Copyright 1987 Star Micronics Co.,Ltd.
INTRODUCTION
This manual describes dot matrix printers as shown below.
It is intended for use as a reference for periodic inspections and maintenance procedures.
This manual is prepared for use at a technical level and not for the general user.
Model Interface Mono/Colour Destination Ver.
NX-1000MULTI-FONT PRINTER Parallel Type Monochrome
NX-1000CMULTI-FONT PRINTER Commodore Type Monochrome
NX-1000COLOUR PRINTER Parallel Type Colour
NX-1000C COLOUR PRINTER Commodore Type Colour
LC-10 MULTI-FONT PRINTER Parallel Type Monochrome
LC-10CMULTI-FONT PRINTER Commodore Type Monochrome
LC-10 COLOUR PRINTER Parallel Type Colour
LC-10C COLOUR PRINTER Commodore Type Colour
NX-1000 II MULTI-FONT PRINTER Parallel Type Monochrome
LC-10 II MULTI-FONT PRINTER Parallel Type Monochrome
• This manual is divided into the following sections:
Chapter 1 General Specifications
Chapter 2 Theory of Operation
Chapter 3 Adjustments
Chapter 4 Parts Replacement
Chapter 5 Maintenance and Lubrication
Chapter 6 Troubleshooting
Chapter 7 Parts List (Ver. 1 and Ver. 1.5)
Chapter 8 Parts List (Ver. 2)
Appendix Explanation of Principle ICs
• First edition : Nov. 1987 Only Monochrome Type
Second edition : Mar. 1988 Add Colour Type
Third edition : Dec. 1988 Add Ver. 1.5 of Parallel Type
Fourth edition : Jul. 1989 Add NX-1000 II and LC-10 II (Ver. 2 of Parallel Type)
Fifth edition : Apr. 1991
Sixth edition : Aug. 1993
Seventh edition :Sep. 1995
Eighth edition :Apr. 1996
Ninth edition :Aug. 1997
Except for
European market
For European
Market
For American
and Asian market
For European and
Pacific market
Ver. 1
and
Ver. 1.5
Ver. 2
1
2
3
4
5
6
7
8
APP.
CHAPTER 1
GENERAL SPECIFICATIONS
1. General Specifications .........................................................................................3
1-1. Parallel Type............................................................................................................ 3
1-2. Commodore Type.................................................................................................... 4
2. External Appearance and Composition .............................................................. 7
2-1. Names of Parts........................................................................................................ 7
2-2. DIP switch settings ................................................................................................. 9
3. Connector Signals .............................................................................................. 11
3-1. Parallel Interface ................................................................................................... 11
3-2. Commodore Interface........................................................................................... 12
1
2
3
4
5
6
7
8
A
– 2 –
GENERAL SPECIFICATIONS
– 3 –
GENERAL SPECIFICATIONS
1. General Specifications
1-1. Parallel Type
Printing
Printing method Serial impact dot matrix
Printing speed 120 characters per second (in Draft pica for Ver. 1 and Ver. 1.5)
30 characters per second (in NLQ pica for Ver. 1 and Ver. 1.5)
150 characters per second (in Draft pice for Ver. 2)
38 characters per second (in NLQ pica for Ver. 2)
Data buffer 4K bytes (for monochrome type), 8K byte (for colour type) when not used for
download characters. 1-Line buffer when using download
Paper feed 2.7 inches/second (during page feed)
Friction and push-tractor feed
Printing direction Draft: bi-directional or unidirectional (selectable), logic seeking
NLQ and graphics: unidirectional, logic seeking
Character set
Standard character set 96 ASCII characters
IBM character set 244 characters (ASCII,international characters, symbols, block graphics)
Downloadable characters Max.192 (draft) or 78 (NLQ)
International character sets 14 sets (USA, France, Germany, England, Denmark I, Denmark II, Sweden,
Italy, Spain I, Spain II, Japan, Norway, Latin America, Denmark/Norway
Dot matrix size
Character matrix 9 × 9 dots (Draft pica)
18 × 23 dots (Courier and Orator pica)
18 × 18 dots (Sanserif pica,elite)
12 × 11 dots (IBM block graphics,pica)
18 × 19 dots (Courier and Orator elite)
18 × 12 dots (Condensed pica)
18 × 10 dots (Condensed elite)
Bit-image graphic 8 × 480 dots at 60 dpi (Single density)
9 × 480 dots at 60 dpi (Single density)
8 × 576 dots at 72 dpi (Plotter mode)
8 × 640 dots at 80 dpi (CRT I)
8 × 720 dots at 90 dpi (CRT II)
8 × 960 dots at 120 dpi (Double density)
9 × 960 dots at 120 dpi (Double density)
8 × 960 dots at 120 dpi (High speed)
8 × 1920 dots at 240 dpi (Quadruple density)
Line spacing 1/6 inch standard 1/8, n/72, or n/216 inch programmable
Column width 80, normal pica 96, normal elite
137, condensed pica 160, condensed elite
Paper
Single sheets 5.5 ~ 8.5 inches wide 0.07 ~ 0.10 mm thick
Fanfold paper 4 ~ 10 inches wide 0.07 ~ 0.10 mm thick (single-ply)
Max, 0.28mm thick (3-ply)
– 4 –
GENERAL SPECIFICATIONS
Printer
Dimensions Height 108 mm (4.3 inches) Width 384 mm (15.1 inches)
Depth 287.5 mm (11.3 inches)
Weight 4.7 kg (10.3 pounds)
Power 120 VAC±10%, 60Hz. 220 VAC±10%, 50/60Hz.
240 VAC±10%, 50/60Hz.
Power consumption Typ. 30W, Max. 60W
Environment Operating temperature: 5 to 40°C (41 to 104°F)
Operating humidity: 10 to 80%, non condensation
Storage temperature: –30 to 65°C (–22 to 149°F)
Storage humidity: 10% to 95% (at 40°C) (no condensation)
Print head 9 Pins
Life: 200 million dots
Ribbon Fabric ribbon cartridge
Monochrome type ........................... Black
Colour type ..................................... Black/cyan/magenta/yellow
Life: 1 million draft characters
Option Automatic sheet feeder
Parallel interface
Interface Centronics-compatible
Synchronization By external supplied strobe pulses
Handshaking By ACK or BUSY signals
Logic level TTL
Connector 57-30360 Amphenol
1-2. Commodore Type
Printing
Printing method Serial impact dot matrix
Print speed 120 characters per second (in Draft pica)
30 characters per second (in NLQ pica)
Data buffer 1-line buffer
Paper feed 2.7 inches/second (during page feed)
Friction and push-tractor feed
Printing direction Draft: bi-directional or unidirectional (selectable), logic seeking
NLQ and graphics: unidirectional, logic seeking
Commodore character sets
Standard graphics Upper-case letters, digits, punctuation and symbols, graphic characters
Standard business Lower- and upper-case letters, digits, punctuation and symbols, graphic charac-
ters
DIN graphics Upper-case letters, international letters, digits, punctuation and symbols, graphic
characters
DIN business Lower- and upper-case letters, international letters, digits, punctuation and
symbols, graphic characters
Downloadable characters Max. 192 (draft) or 80 (NLQ)
International characters sets 10 sets (England, USA, France, Germany, Denmark I, Denmark II, Sweden I,
Italy, Spain, Sweden II)
– 5 –
GENERAL SPECIFICATIONS
Printing
Dot matrix size
Character matrix 9 × 9 dots (Draft pica)
18 × 23 dots (Courier and Orator pica)
18 × 18 dots (Sanserif pica,elite)
7 × 11 dots (Block graphics,pica)
18 × 19 dots (Courier and Orator elite)
18 × 12 dots (Condensed pica)
18 × 10 dots (Condensed elite)
Bit-image graphic 7 × 480 dots at 60 dpi (Single density)
8 × 480 dots at 60 dpi (Single density)
7 × 960 dots at 120 dpi (Double density)
8 × 960 dots at 120 dpi (Double density)
8 × 960 dots at 120 dpi (High speed)
8 × 1920 dots at 240 dpi (Quadruple density)
Line spacing 1/6 inch standard 1/8, n/72, or n/216 inch programmable
Column width 80, normal pica 96, normal elite
137, condensed pica 160, condensed elite
Paper
Single sheets 5.5 ~8.5 inches wide 0.07 ~ 0.10 mm thick
Fanfold paper 4 ~ 10 inches wide 0.07 ~ 0.10 mm thick (single-ply)
Max. 0.28mm thick (3 ply)
Printer
Dimensions Height 108 mm (4.3 inches) Width 384 mm (15.1 inches)
Depth 287.5 mm (11.3 inches)
Weight 4.7 kg (10.3 pounds)
Power 120 VAC±10%, 60Hz. 220 VAC±10%, 50/60Hz.
240 VAC±10%, 50/60Hz.
Power consumption Typ. 30W, Max. 60W
Environment Operating temperature: 5 to 40°C (41 to 104°F)
Operating humidity: 10 to 80%, no condensation
Storage temperature: –30 to 65°C (–22 to 149°F)
Storage humidity: 10% to 95% (at 40°C) (no condensation)
Print head 9 Pins
Life: 200 million dots
Ribbon Fabric ribbon cartridge
Monochrome type ........................... Black
Colour type ..................................... Black/blue/red/yellow
Life: 1 million draft characters
Option Automatic sheet feeder
Commodore interface
Interface Serial mode, for Commodore computers
Synchronization By external supplied clock (synchronous serial)
Logic level TTL
Connector 6-pin DIN
– 6 –
GENERAL SPECIFICATIONS
Fig. 1-1 External Dimensions
– 7 –
GENERAL SPECIFICATIONS
2. External Appearance and Composition
2-1. Names of Parts
Fig. 1-2 Front and rear views of the printer
– 8 –
GENERAL SPECIFICATIONS
Fig. 1-3 Diagram of Internal Composition
– 9 –
GENERAL SPECIFICATIONS
2-2. DIP Switch Settings
Parallel Type Commodore Type
Fig. 1-4 The DIP Switch is located under the Printer Cover
2-2-1. Parallel Type
Switch Function ON OFF Factory
1-1 Page length 11 inches 12 inches ON
1-2 Auto CR Yes No ON
1-3 Orator lower case Small caps Lower case ON
1-4 Auto sheet feeder Inactive Active ON
1-5 Paper-out detector Enabled Disabled ON
1-6 Printer mode Standard IBM ON
Character set (Std. Mode) Italics Graphics
Character set (IBM Mode) Set #2 Set #1
1-8 Auto LF No Yes ON
2-1 Usage of RAM Buffer Download ON
2-2 ON
2-3 International character set (See right) ON
2-4 ON
International character sets:
Country 2-2 2-3 2-4
U.S.A. ON ON ON
France OFF ON ON
Germany ON OFF ON
England OFF OFF ON
Denmark I * ON ON OFF
Sweden OFF ON OFF
Italy ON OFF OFF
Spain I OFF OFF OFF
* Denmark/Norway when switches 1-6
and 1-7 are both OFF.
A. Except for U.S.S.R. market
1-7 ON
Switch Function ON OFF Factory
1-1 Page length 11 inches 12 inches ON
1-2 Auto CR Yes No ON
1-3 Character set Standard IBM ON
1-4 Auto sheet feeder Inactive Active ON
1-5 Paper-out detector Enabled Disabled ON
1-6 Printer mode Standard IBM ON
1-7 Character set Set #1 Set #2 ON
1-8 Auto LF No Yes ON
2-1 Usage of RAM Buffer Download ON
2-2 Italic OFF ON ON
2-3 ESC 4/ESC 5 (*1) Italic MSB ON
2-4 Not used — — ON
*1 The switch 2-3 is valid only in the standard printer mode.
B. For U.S.S.R. market
– 10 –
GENERAL SPECIFICATIONS
2-2-2. Commodore Type
Switch Function ON OFF Factory
1-1 Auto LF Yes No ON
1-2 Paper out detector Enable Disable ON
1-3 Device number No. 4 No. 5 ON
1-4 Page length 11 inches 12 inches ON
1-5 Operating mode
Commodore
ASCII ON
1-6 ON
1-7 International character set (See right) ON
1-8 ON
1-9 Commodore characters Standard DIN ON
1-10 Auto sheet feeder Inactive Active ON
International character sets:
Country 1-6 1-7 1-8
Commodore * ON ON ON
U.S.A. OFF ON ON
Germany ON OFF ON
Denmark I OFF OFF ON
France ON ON OFF
Sweden I OFF ON OFF
Italy ON OFF OFF
Spain OFF OFF OFF
* England (Switch 1-5 is OFF)
– 11 –
GENERAL SPECIFICATIONS
3. Connector Signals
3-1. Parallel Interface
Pin No. Signal Name Direction Functional Description
Goes from High to Low (for at least 0.5 microseconds) when data
are valid.
Eight-bit character data. DATA8 is the most significant bit; DATA
1 is the least significant bit.
High is logic 1 and Low is logic 0.
Approx.9-Microsecond Low pulse acknowledges receipt of data.
Low when the printer is ready to accept data.
Goes High if the printer runs out of paper.
Can be held Low permanently by turning DIP switch 1-5 off.
High when the printer is on-line.
Unused
Signal Ground
Printer’s chassis ground, isolated from signal ground.
External supply of +5V DC.
Twisted pair return signal ground level.
Low input resets the printer to its power-up condition.
Goes Low to signal that the printer cannot print due to an error
condition.
External ground
Unused
Always High.
1 STROBE IN
2 DATA 1 IN
3 DATA 2 IN
4 DATA 3 IN
5 DATA 4 IN
6 DATA 5 IN
7 DATA 6 IN
8 DATA 7 IN
9 DATA 8 IN
10 ACK OUT
11 BUSY OUT
12 PAPER OUT OUT
13 SELECTED OUT
14, 15 (NC)
16 SIGNAL GND
17 CHASSIS GND
18 +5VDC OUT
19 ~ 30 GND
31 INPUT-PRIME IN
32 ERROR OUT
33 EXT GND
34, 35 (NC)
36 SELECT-IN IN
– 12 –
GENERAL SPECIFICATIONS
3-2. Commodore Interface
Pin No. Signal Name Direction Functional Description
1 SRQ OUT
2 GND
3 ATN IN
4 CLK IN
5 DATA IN/OUT
6 RESET IN
Not used.
Signal ground.
Serial Attention In
High.....................Signifies the data transfer mode.
Low .....................Signifies the command transfer mode.
Serial Clock In
The printer begins reading data on the rising edge of this signal.
Serial Data In/Out
IN: Conveys commands and data from the computer to the printer
OUT: High indicates printer ready Low indicates printer busy.
When this signal level goes low, the printer is initialized
and the memory buffer is cleared.
CHAPTER 2
THEORY OF OPERATION
1. Block Diagram ..................................................................................................... 15
2. Main Logic Board ................................................................................................ 16
2-1. Data Input Operation............................................................................................. 16
2-1-1. Parallel Interface ............................................................................................... 16
2-1-2. Commodore Interface.......................................................................................17
2-2. General Flow Chart ............................................................................................... 19
2-2-1. Editing ............................................................................................................... 20
2-2-2. Print Head Driving Circuit ................................................................................ 20
2-2-3. Carriage Motor Driving Circuit......................................................................... 20
2-2-4. Carriage Motor Speed Control......................................................................... 21
2-2-5. Paper Feed Motor Driving Circuit.................................................................... 22
2-3. Reset Circuit .......................................................................................................... 23
2-4. Reset by +5V Line Voltage Detection .................................................................. 24
2-5. Protection Circuit .................................................................................................. 24
3. Power Supply Unit .............................................................................................. 24
4. Mechanisms......................................................................................................... 25
4-1. Print Head Mechanism.......................................................................................... 25
4-2. Print Head Carrying Mechanism .......................................................................... 25
4-3. Ink Ribbon Feed Mechanism................................................................................ 26
4-4. Paper Feed Mechanism ........................................................................................ 27
4-5. Detectors ............................................................................................................... 28
1
2
3
4
5
6
7
8
A
– 14 –
THEORY OF OPERATION
– 15 –
THEORY OF OPERATION
1. Block Diagram
The block diagram of this printer is shown in Fig. 2-1.
Parallel Type Commodore Type
Fig. 2-1 Block Diagram
(1) Main Logic Board
This board receives data from the host computer and stores it in the RAM in the order of arrival. The CPU on this
board reads the data from the RAM and edits it according to the program stored in the ROM.
When the editing is completed, various drive signals from the CPU are sent to the printer mechanism to perform
printing.
<Explanation>
1 CPU M50734SP
• Controls this printer.
2 ROM µPD27C512 64K-byte
• Contains the program which executes control of the printer.
3 RAM 8K-byte (Monochrome type), 32K-byte (Colour type)
• Used as stack area, work area and data buffer of the CPU.
4 Parallel interface (Parallel type only)
5 Commodore interface (Commodore type only)
6 Gate array (custom IC)
• Inputs or outputs several signals.
7 Driver
• The data edited by the CPU and gate array are sent to the printer mechanism after conversion to the signal
for the print head drive, carriage motor drive, and paper feed motor drive respectively.
8 Control Panel Circuit
This panel circuit is for manual operation of the printer.
(2) Printer Mechanism
The printer mechanism consists of a print head, carriage motor, paper feed motor, and detectors.
(3) Power Supply Unit
AC power is converted to DC24V and DC5V.
– 16 –
THEORY OF OPERATION
2. Main Logic Board
2-1. Data Input Operation
2-1-1. Parallel Interface (Parallel type only)
Communications between the host computer and this printer are facilitated via parallel connectors. This section explains
the handshake of this interface.
The data input circuit of this interface is shown in Fig. 2-2.
Fig. 2-2 Data Input Circuit with Parallel Interface
The following is an explanation of this handshake.
(1) When the BUSY signal is LOW (Ready), the host computer outputs 8- bit data 1 through 8 to the connector CN1.
Pin 1 carries the STROBE pulse signal from the host computer to the printer.
This signal is normally held HIGH by the host computer. When the host computer has data ready for the printer,
it sets this signal to LOW for at least 0.5 µS.
(2) The gate array of the main logic board reads data 1 through 8 at the time of STROBE signal fall, and then turns the
BUSY and P-BUSY signals to low.
(3) When the BUSY signal of the gate array is set to LOW, the BUSY signal of connector CN1 will be turned to HIGH,
notifying the host computer that data cannot be accepted.
(4) Ver. 1 Board
When the P-BUSY signal goes LOW, the CPU INT1 signal also goes LOW, causing a CPU interrupt.
If such an interrupt occurs in the CPU, set the RD signal to LOW, and read the gate array into the CPU.
Ver. 1.5 Board and Ver. 2 Board
The CPU is informed via the D0 data line that the P-BUSY terminal is LOW. Because of this, set the RD signal to
LOW and read the gate array into the CPU.
(5) Upon completion of the data reading, the CPU notifies the host computer of the data receivable state by setting the
BUSY signal of connector CN1 and the ACK signal to LOW for a certain period of time.
This concludes the explanation of the parallel interface handshake. The following chart describes the timing chart
of the handshake.
– 17 –
THEORY OF OPERATION
Fig. 2-3 Timing Chart of Parallel Interface
2-1-2. Commodore Interface (Commodore type only)
The commodore interface is a serial interface which can be connected to COMMODORE network host computers.
The data input circuit with a Commodore interface is shown in Fig. 2-4.
Fig. 2-4 Data Input Circuit with Commodore Interface
Two types of the handshake mode are used with this Commodore interface:
Non-EOI handshake and EOI handshake. The timing chart of the Non-EOI handshake mode is shown in Fig. 2-5, and that
of the EOI handshake mode in Fig.2-6.
– 18 –
THEORY OF OPERATION
Fig. 2-5 Timing Chart of Non-EOI Handshake Mode
Fig. 2-6 Timing Chart of EOI Handshake Mode
(1) Non-EOI handshake
This is a regular data transmission handshake.
1. The host computer acknowledges that the DATA line is low (data reception is completed), raises the CLK, and
notifies the printer that the host computer is ready to send (data or commands).
2. The printer sends information to the host computer by raising the DATA line to show that the printer is ready
to receive more data.
3. The host computer sends information to the printer that data is available after the next raising of the CLK, by
lowering the CLK.
4. After storing data, the host computer indicates that the data is available by raising the CLK.
The printer reads the data at the rising edge of the CLK. Then the host computer lowers the CLK and opens
the DATA line, acknowledging that the printer is in READY mode (DATA line is high), and moves to the next
bit handshake.
5. Sending 8-bit data is the same as above. When transmission is completed, the printer sends information to the
host computer that the receiving of data is finished by lowering the DATA line.
(2) EOI handshake
This handshake is used to show that the next data bytes are the last data.
1. The host computer acknowledges that the DATA line is LOW (receiving data is finished), and sends
information to the printer that the host computer is ready to send data (including commands) by raising the
CLK.
2. The printer sends information to the host computer that the printer is ready to receive data by raising the DATA
line.
At the rising edge the 500 µs timer starts.
(Until now this has been operating the same as the Non-EOI handshake.) From the starting of the timer, the
host computer keeps the CLK high for more than 500 µs to indicate EOI.
3. If the CLK does not fall within 500 µs, the printer acknowledges the EOI, and lowers the DATA line to LOW.
4. The printer sends information to the host computer that it is ready to receive data by raising the DATA line
again.
To send 8-bit data, follow the preceding Non-EOI handshake procedure.
– 19 –
THEORY OF OPERATION
2-2. General Flow Chart
A general flow chart of editing and printing operations is presented in Fig. 2-7.
Fig. 2-7 General Flow Chart of Editing and Printing
– 20 –
THEORY OF OPERATION
2-2-1. Editing
Data stored in the RAM is read out sequentially by the CPU and then edited according to a function code that has been
specified in advance.
This editing takes places until the CR or CR + LF code appears or the line buffer becomes full.
2-2-2. Print Head Driving Circuit
Edited print data is output to terminal Q of LS273 in the gate array through the CPU data bus, as regulated by the issue
timing of a WR signal. However, as for pin 9 (HD9) of the print head, the data is output to the same terminal upon issue
of the next WR signal. When all the data is received for printing, an energized time control signal is output from port PO4
of the CPU. This allows the print data to be output to HD-1 ~ 9 of the gate array. When the print data is HIGH, the transistor
TR9 will be turned ON for 380 µS (Ver 1 and 1.5), 340 µs (Ver 2), energizing the print head solenoid to drive the print
head.
Fig. 2-8 Print Head Driving Circuit
2-2-3. Carriage Motor Driving Circuit
This printer employs a stepping motor as the carriage motor. Unlike regular motors on the market, this stepping motor
will not operate just by connecting it to a power source. The motor operates only when a drive pulse is fed to it, but even
then, it turns only a certain angle.
This stepping motor is characterized by 4-phase stepping. Control of the motor is facilitated by phase 1-2 excitation. The
following is the description of the carriage motor drive circuit and the control signal generated by the phase 1-2 excitation
method.
– 21 –
THEORY OF OPERATION
Fig. 2-9 Carriage Motor Driving Circuit
Fig. 2-10 Carriage Motor Driving Signals
The utilization of voltage applied to the carriage motor is
described below:
Voltage applied to the carriage motor is changed by setting port
P30 of the CPU to HIGH or LOW and by turning transistors
TR6 and TR1 ON or OFF.
When TR1 is ON, +24V is supplied to the carriage motor and
when TR1 is OFF, +5V is supplied to the motor via diode D1.
2-2-4. Carriage Motor Speed Control
Since the carriage motor is a stepping motor, the carriage can be stopped at a desired position by controlling acceleration
and deceleration. The carriage can also move backward.
The rotational speed of the carriage motor is set by the number of pulses per time unit. The character pitch (horizontal
character size) in each print mode is determined by changing this rotational speed (or carriage transfer speed).
(1) At start-up of the motor:
The number of pulses input to the motor increase in steps (36 altogether), reaching a certain frequency.
(2) To stop the motor:
The number of pulses input to the motor decreases in steps (36), in order to gradually bring the motor to a halt.
(3) When printing is carried out:
Pulses of a uniform pulse width are supplied for printing.
Mode Voltage Application
Operation: +24V Motor Drive
Standby: +5V Holding Bias
– 22 –
THEORY OF OPERATION
2-2-5. Paper Feed Motor Driving Circuit
Again, a stepping motor is employed as the paper feed motor, which turns a certain angle only when a drive pulse is
received. This 4-phase stepping motor is controlled by the phase 1-2 excitation method. The following is the description
of the paper feed motor drive circuit and the control signal generated by the phase 1-2 excitation method.
Fig. 2-11 Paper Feed Motor Driving Circuit
Fig. 2-12 Paper Feed Motor Driving Signals
The utilization of voltage applied to the paper feed motor is described as follows.
Mode Voltage Application
Operation +24V Motor Drive
Standby: +5V Holding Bias
Voltage to the paper feed motor is changed by setting CPU port P31 to LOW or HIGH and by turning transistors TR7 and
TR2 ON or OFF.
When TR2 is turned on, +24V is applied to the paper feed motor.
When TR2 is turned off, +5V is supplied to the motor via diode D2.
– 23 –
THEORY OF OPERATION
2-3. Reset Circuit
The RESET signal initializes the circuit elements and prevents operation errors when the power is turned on.
The RESET signal is output for approx. 34ms. when the power is turned on, or while the RESET ( INPUT-PRIME ) signal
is being output from the host computer.
Fig. 2-13 Reset Circuit and Protection Circuit.
• Power On Reset
1 When the power is turned on, the RESET signal output from Pin 5 of IC6 (M51953BL) for approx. 34 msec. This time
length is determined by external capacitor C18 (0.1µF), and it can be calculated by the following formula.
T = 0.34 × C18 (pF) µsec.
2 This LOW signal triggers RESET command to the CPU and the RESET terminal ( RES ) of the gate array.
3 Resetting the CPU and the gate array will ignore all the drive signals for the carriage motor, the paper feed motor and
the print head, preventing operation errors at power ON.
• Reset by Input Prime Signal from Host Computer
1 The input prime signal from the host computer is output to pin 31 of the connector CN1.
2 This output signal will set the terminal INIT 2 of the CPU to LOW, executing interruption. Then, the CPU will be
initialized.
– 24 –
THEORY OF OPERATION
2-4. Reset by +5V Line Voltage Detection
A voltage-detecting IC (IC6 in Fig.2-13) detects momentary drops in voltage or unstable voltage supply (due to power
failures, etc.) on the +5V line. If the voltage on the +5V line falls below 4.25V, the RESET signal appears at the output
terminal of the voltage-detecting IC.
Fig. 2-14 Equivalent Circuit of Fig. 2-15 Operational Timing Chart
Voltage-Detecting IC
2-5. Protection Circuit
This printer is provided with a protection circuit which shuts off the print head and motor driving circuits in the event of
a CPU malfunction. (Refer to Fig.2-13)
The CPU normally outputs a LOW level signal from the terminal (WD OUT).
However, if the CPU malfunctions, it can not output this signal.
When the LOW level signal is not output from the CPU, the input terminal (Cd) of the voltage-detecting IC goes to LOW
and the RESET signal is output from the output terminal (OUT) of the voltage-detecting IC. By this signal, the CPU and
the gate array are reset and the print head, the carriage motor and paper feed motor driving signals are ignored, protecting
the printer from the CPU runaway.
3. Power Supply Unit
The power supply circuit converts the incoming AC power to DC voltages, +5V and +24V.
Voltage Tolerance Application
+24V DC24V±5% To drive print head, carriage motor, paper feed
motor.
+5V DC5V±2.5% To supply power to CPU, ROM, RAM, TTL
and ICs and to retain carriage motor and paper
feed motor.
– 25 –
THEORY OF OPERATION
4. Mechanism
4-1. Print Head Mechanism
The print head consists of 9 needle wires and 9 print solenoids.
The following explains how each needle wire operates during printing.
(1) When the print solenoid is energized, the clapper is attracted by the iron core and the needle wire is driven toward
the platen.
(2) This needle wire hits the platen via the ink ribbon and paper. A single dot is printed on the paper.
(3) When the print solenoid is de-energized, the needle wire is returned to its original position by rebound energy and
spring and clapper holder (leaf spring) force.
Fig. 2-16 Outline of Print Head Mechanism
4-2. Print Head Carrying Mechanism
The print head carrying mechanism consists mainly of a carriage, timing belt, carriage motor, and home position detector.
(1) Carriage
The carriage is supported horizontally by means of the carriage stay and rear angle, and it moves from side to side
with the print head mounted above it. A timing belt is clamped to the base of the carriage and a shield plate is mounted
at the base for home position detection.
(2) Timing Belt
The timing belt is suspended between the timing pulley of the carriage motor and the timing pulley of the tension
lever, and it maintains a constant tension.
The timing belt is also clamped to the base of the carriage so that it can move the carriage accurately with driving
force from the carriage motor.
(3) Carriage Motor
The carriage motor is a PM (Permanent Magnet) type, four-phase and 48-pole pulse motor, which is driven by pulse
signals from the control circuit. The rotational rate depends on the number of pulses per unit time. By varying this
rotational rate (that is, the carriage carrying rate), the size of the horizontal letters can be changed in each print mode.
– 26 –
THEORY OF OPERATION
Fig. 2-17 Print Head Carrying Mechanism
4-3. Ink Ribbon Feed Mechanism
The ink ribbon feed mechanism is linked to the print head carrying mechanism described previously so that the ink ribbon
is wound up automatically while the carriage moves left or right.
The ribbon feed mechanism is driven by torque from the carriage motor, and carriage movement allows the idler gear to
rotate.
This rotation is conveyed sequentially to the gears that work to wind the ribbon. The carriage is equipped with a clutch
lever so that the direction of cassette gear rotation remains constant regardless of the direction of the idler gear rotation.
Fig. 2-18 Ribbon Feed Mechanism
– 27 –
THEORY OF OPERATION
Not Linked
4-4. Paper Feed Mechanism
The paper feed motor is a PM type, four-phase and 48-pole pulse motor.
Minimum paper feed is set at 1/216 inch.
There are two ways of feeding paper available with this printer: Friction method and Tractor method. You can select one
of the two methods, using the release lever.
Position of release lever [1] [2]
Linkage between tractor
gear and tractor clutch
Platen roller and holder roller Pressured Not
Release lever position detector Closed Open
Paper feeding method Friction Tractor
(1) Friction Method
Friction method is selected when the release lever is position [1].
With this method, paper is pressed between the platen roller and the holder roller therefore, paper is fed as the rollers
turn.
As the paper feed motor is driven, the motor gear, through the idler gear, turns the platen gear in the paper feeding
direction. However, since the tractor gear and the tractor clutch are not linked at this time, the tractor unit will not
be driven.
(2) Tractor Method
Tractor method is selected when the release lever is position [2].
As described below, paper feeding is facilitated by rotation of the sprocket pin of the tractor unit. When the tractor
method is selected, the tractor gear is linked to the tractor clutch, enabling the drive force generated by the paper
feed motor to be transferred to the tractor unit via the idler gear and the platen gear.
Fig. 2-19 Paper Feed Mechanism
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