OKIDATA ML321 TURBO (01) PDF MANUAL


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PDF Content Summary: Page: 1 Service Guide ML320/321Turbo Chapter 0 About This Manual ML320 Turbo // ML321 Turbo Dot Matrix Printers Adobe Acrobat printable reference copy of the OKIDATA Service Training Manual. 09/17/97 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. Okidata is a registered trademark, and OkiPage is a trademark of Oki Electric Industry Co., Ltd. HP, LaserJet and PCL5e are trademarks of Hewlett-Packard Co. Adobe and Acrobat are trademarks of Adobe Systems Incorporated. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Table of Contents Page Service Guide ML320/321Turbo 0 About This Manual Front Cover 1 1 Configuration 1.1. Standard Printer Configuration 2 1.2 Options 3 2 Operation Description ....2.1.1 Summary 4 ....2.1.2 Microprocessor and the Peripheral Circuit 5 ....2.1.3 Initialization 6 ....2.1.4 Parallel Interface Control 7 ....2.1.5 Print Control 8 ....2.1.6 SP/LF Motor Control 9 ....2.1.7 Operation Panel 10 ....2.1.8 Alarm Circuit 11 ....2.1.9 Power Supply Circuit 12 2.2 Mechanical Operation 13 ....2.2.2 Spacing Operation (See Figure 2-4.) 14 ....2.2.3 Head Gap Adjusting (See Figure 2-5.) 15 ....2.2.4 Ribbon Drive (See Figure 2-6.) 16 ....2.2.5 Paper Feed Operation 17 ....2.2.6 Paper Detection Mechanism (See Figure 2-15.) 18 ....2.2.7 Automatic Sheet Feed 19 ....2.2.8 Paper Park Function (Continuous sheet paper) 20 3 Parts Replacement 3. ASSEMBLY/DISASSEMBLY 21 3.1 Precautions for Parts Replacement 22 3.2 Service Tools 23 3.3 Disassembly/Reassembly Procedure 24 ....3.3.1 Printhead 25 ....3.3.2 Ribbon Protector 26 ....3.3.3 Pull-up Roller Assy 27 ....3.3.4 Upper Cover, Access and Sheet Guide Assy 28 ....3.3.5 Gear Case Assy 29 ....3.3.6 PC Connector 30 ....3.3.7 Space Motor, Guide Roller Assy 31 ....3.3.8 Space Rack 32 ....3.3.9 Carriage Cable 33 ....3.3.10 Backup Roller Holder Assy 34 ....3.3.11 Platen Assy 35 ....3.3.12 Driver Board (SDDV) 36 ....3.3.13 LF Motor 37 ....3.3.14 Operation Panel PCB (LEOP) 38 Table of Contents Page ....3.3.15 Control/Power Supply Board (SDCT) 39 ....3.3.16 Transformer Assy 40 ....3.3.17 Change Lever and Gears 41 ....3.3.18 Carriage Shaft 42 ....3.3.19 Paper Pan 43 ....3.3.20 Rear Tractor Assy 44 ....3.3.21 Rear Pressure Assy 45 ....3.3.22 Switch Lever 46 4 Adjustments 4. ADJUSTMENT 47 5 Periodical Maintenance 5.1 Cleaning 48 5.2 Lubrication 49 6 Troubleshooting 6.1 Items to Check Before Repair 50 6.2 Troubleshooting Table 51 6.3 Lamp Display 52 6.4 Connection Circuit Check for Printhead and SP/LF Motor 53 6.5 Troubleshooting Flow Chart 54 A Centronics Parallel Interface A. PCB LAYOUT 55 B Parts Listing Parts Listing 56 Figure 11-1 Upper Cover Assy 57 Figure 11-2 Printer General Assy 58 Figure 11-3 Printer Unit 59 Figure 11-4 Carriage Assy 60 Figure 11-5 Option Spare Parts 61 C Software Diagnostics and Adjustments RS-232C SERIAL INTERFACE BOARD 62 2. OPERATION DESCRIPTION 63 ....2.2.1 Operation at power on 64 ....2.2.2. RS-232C interface 65 2.3 Communication Procedure Flowchart 66 3. TROUBLESHOOTING FLOWCHART 67 3.3 Local Test 68 Page: 2 Service Guide ML320/321Turbo Chapter 1 Configuration 1.1. Standard Printer Configuration This printer consists of the following assemblies: Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 3 Service Guide ML320/321Turbo Chapter 1 Configuration 1.2 Options (1) Cut sheet feeder unit (CSF) Single-bin CSF (2) Pull-tractor assy (3) Bottom push tractor unit (4) Roll paper stand (Narrow only) (5) Serial I/F - RS-232C Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 4 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.1 Summary Fig. 2-1 shows the block diagram of the printer. The control board is made up of the microprocessors, peripheral circuits, drive circuits, sensors and interface connectors. The power to the control board is supplied by the power board through the connector cord. The power to other electrical parts is also distributed through the connectors within the control board. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 5 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.2 Microprocessor and the Peripheral Circuit (1) Microprocessor (Q7: 67X640) This processor is a CMOS single-chip computer with integrated peripheral device functions and a 16-bit MPU core, all OKI original architecture. The processor has a 20-bit address bus and a 16-bit data bus. It is capable of accessing up to 1M word program memory and 1M bytes of data memory. The following characteristics are also provided: - Built-in type data memory of 512 bytes - 8-bit 4-channel A/D converter x 1 - 16-bit automatic reload timer x 2 - 8-bit serial port x 2 - 8-bit parallel port 3 3 (bitwise I/O specification available) And others. The function of this microprocessor is to provide a central mechanism for the entire printer by executing the control program through the LSI and driver circuits. (2) Program ROM This is a 256 x 16 bits (4M bit) [MAX] EPROM with the control program for the printer stored. The MPU executes instructions under this program. The program ROM is assigned to the program memory area of the MPU and is fetched by the PSEN signal of the MPU. The following shows the operation of the memory access. (3) RAM (MSM51C464A-80RS) The RAM is CMOS dynamic RAM with (64K x 4-bit) x 2 configuration, and used as buffers (such as receiving buffer, printing buffer, DLL buffer and working buffer). The following shows examples of the memory access operation. (4) EEPROM The EEPROM is a CMOS serial I/O type memory which is capable of electrically erasing and writing 1,024 bits. The EEPROM contains menu data. The following shows the memory access operation. (5) LSI This LSI detects and controls the SP motor speeds by monitoring the two-phase sensor signals obtained from the DC motors and modifying the excitation phases as appropriate. This LSI is connected in multiplex to the MPU. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 6 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.3 Initialization This printer is initialized when the power is turned on or when the I-PRIME-N signal is input from the host side via the parallel interface. For the initialize operation, the RST-N signal is first output from the reset circuit to reset the MPUs and LSIs. When resetting ends, the program starts and the LSIs are reset by MPU via LSIRST-N. Reset operation by I-PRIME starts the program to initialize, but does not reset the MPU. The program sets the mode of the LSI including the MPU, checks the memories (ROMs and RAMs), then carries out carriage homing, and determines the LF motor phase. Finally, the program establishes the interface signals (P-I/F: ACK-P signal sending, and S-I/F: BUSY-N signal off) and lights the SELECT lamp. When the ready state is set, the host is informed that the printer is ready to receive data. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 7 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.4 Parallel Interface Control The parallel data input from the host to the interfaced LSI is latched to its internal register at the falling edge of the STROBE-N signal. At the same time, the LSI sets the BUSY signal to the high level to inform the host that the data is being processed, and outputs the RXD signal to inform the MPU of data reception. The data is read upon receiving the RD-N signal from the MPU. When the data processing ends, the BUSY signal is set to off and the ACK-N signal in sent to request the next data. When reception is impossible because the buffer is full, the BUSY signal is sent to stop data transmission. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 8 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.5 Print Control Print data is transmitted as parallel data (HEAD1-HEAD9) from the LSI to the print head. The LSI generates the print timing and drive time. Print Compensation Control The print compensation methods are shown below: (a) Voltage compensation (See 2.1.8 "Alarm Circuit." ) (b) Temperature compensation (See 2.1.8 "Alarm Circuit." ) (c) Pin stroke compensation (d) Simultaneous Compensation of the number of impact pins The MPU is provided with the compensation table for each pin to compensate as necessary. Number of impact pins Few < ----- > Many Drive time Short < ------ >Long (e) Print mode compensation According to the thickness of the printing medium, the print mode is compensated as shown in the table below Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 9 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.6 SP/LF Motor Control (1) Space motor control The SP motor driver (HA13412) drives the three-phase brushless motor based on the phase signal (SPU, SPV and SPW) and the speed instruction data from the LSI. The MPU can identify the current speed of the space motor by measuring through the LSI the pulse length of the output (øA, øB) of the slit encoder included in the space motor. By comparing the target speed for each print mode with the actual current speed to change the speed instruction data, the motor speed is increased or decreased to maintain the specified speed for each print mode. (2) Encoder disk In the operation of the spacing motor, the PHASE-A and PHASE-B signals are generated when the encoder disk interrupts the photo sensor. The LSI divides these edge pulse signals in accordance with the print pitch, and sends the IPT signal to provide dot-on timing and carriage position detection timing. (3) LF motor control The LF motor driver (MTD2005F) drives the LF motor in two-phase or 1-2 phase bipolar, based on the phase changeover data and the output current data from the LSI. The data from the LSI is processed by a specific register contained in the LF motor driver to measure the overdrive time and to change the phase. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 10 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.7 Operation Panel The clock synchronization OPCLK signal of the LSI is used to input the switch data and output the LED data through the operation panel control LSI (IC1: BU5148S). A 2-byte (15 bits + 1 even parity bit) command signal (OPTXD) is transmitted to the LSI(BU5148S) in synchronization with the OPCLK signal. The LSI decodes this command and when it is found to be legal, returns a 2-byte command response back to the LSI which includes data on Switch information, LED status, receive command ACK/NAK and 1 odd parity bit. Any transmission errors found cause the command to be reissued after the transmission of the OPCLR-N signal. ote: From the illustration above, you can see that the command and the command response are output at the same time. This is because the bit 0 to bit 3 the OPRXD signal are fixed so that the response can be returned before decoding the command. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 11 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.8 Alarm Circuit (1) Head drive time alarm circuit This circuit monitors the drive time using the HDALM signal interlocked with the overdrive signal of each drive circuit. If the drive time of any drive circuit exceeds the specified time, the drive fault alarm circuit sends an ALARM-N signal to turn on the SCR (SO). This causes the secondary coil (40V) of the transformer to short-circuit, causing an overcurrent to flow through the primary coil and open the AC fuse (transformer assy). (2) Alarm processing when DC power is low. + 40V is converted into the POWLEV signal (0V to +5V) by R28 and R29 and input into the A/D port of the MPU to control the drive time and the print speed (pass number) of the head. (a) Head drive time The head drive time is lengthened to compensate for the amount of voltage drop by monitoring the POWLEV signal once every 500 m sec. to control and maintain the impact necessary for each printing pin at the fixed value. (b) Print Speed (3) Head overheat alarm The voltage of the output TSD signal of the thermistors, one of which is in the printhead and the other in the printhead driver, is monitored by the CPU/AD port to control the voltage - When the temperature is between a°C and 119°C, the mode switches sequentially to higher level. When the temperature falls below ß°C, the mode switches to lower level. - When the temperature exceeds 119°C, printing stops. - When temperature gradient is steep, the higher mode is specified directly. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 12 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.1.9 Power Supply Circuit This power supply circuit supplies the +5VDC, +8VDC, +40VDC, 10VAC. The uses of output voltages and signals are described below. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 13 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2 Mechanical Operation 2.2.1 Printhead Mechanism and Operation (See Figure 2-2 below). The printhead is a spring charged 9-pin driving head using a permanent magnet. It is attached to the carriage, which moves parallel to the platen. Electrically, this unit is connected to the control circuits through the control board. (1) The printhead configuration The printhead is composed of the following parts: (a) Wire guide (b) Spring assembly (Wire, Armature, Spring, Yoke, Spacer) (c) Magnet assembly (Magnet, Core, Coil, Yoke) (d) Printed circuit board (e) Fin (2) Printhead Operation (See Figure 2-3 below). (a) When the printhead is idle, the armature is attracted by a permanent magnet and the spring fixing the armature is compressed. The print wires fixed to each armature are thus concealed under the wire guide. (b) When a signal for a character to be printed is detected, a current flows through the coil. When the coil is activated, the magnetic flux (caused by the permanent magnet between the armature and the core) is canceled to eliminate the attracting force. The armature is driven in the direction of the platen by the force of the armature spring. The print wire fixed to the armature protrudes from the tip of the wire guide, strikes the paper through the ribbon and prints a dot on the paper. (c) After the character has been printed, the armature is magnetically attracted again and the print wires are again concealed under the wire guide. A thermistor in the printhead prevents burning caused by overheating of the coil during extended continuous bi-directional printing. When the temperature of the coil exceeds a predetermined limit (about 119°C) the control circuit detects a thermistor signal. Printing will then be intermittent or stop completely until the coil temperature falls below the limit value. Figure 2-3 Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 14 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.2 Spacing Operation (See Figure 2-4 below). The spacing mechanism consists of a carriage shaft mounted in parallel with the platen, and a carriage frame that moves along the shaft. It is driven by a DC motor mounted on the bottom of the carriage frame. Items included in the spacing mechanism are as follows: (a) DC motor with motor gear (b) Carriage frame (stationary yoke and motor driver board included) (c) Carriage shaft (d) Space rack (e) Sensor (f) Encoder disk (1) Spacing operation The carriage frame, on which the printhead and space motor are mounted, moves along the carriage shaft parallel to the platen. When the spacing motor rotates counterclockwise, the driving force is transmitted to the motor gear. As the motor gear rotates, the carriage moves from left to right. Mechanically, it is designed in such a way that for every revolution of the DC motor, the carriage frame moves 0.8 inch (20.32 mm). At the same time the encoder disk rotates together with the motor and passes through the sensor. The position of the carriage frame can be determined by counting the interrupts detected by the sensor. In the same way, the rotation of the space motor can be recognized and controlled by measuring the cycle of interrupts detected by the sensor. Figure 2-4 Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 15 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.3 Head Gap Adjusting (See Figure 2-5 below). The head gap adjusting lever moves back and forth to tilt the carriage frame, altering the gap between the printhead and the platen. The adjusting screw, which is connected to the adjusting gear rotates when the adjusting lever is moved creating a fine gap adjustment. If the adjusting gear is pushed down, the adjusting screw can be turned with a screw driver to change the coarse gap adjustment. When the adjusting lever is set to range 2 - 3, the contact attached to the under side of the carriage cover will connect with the contact of the space motor PC board. The printer will reduce the printing speed automatically to ensure that adequate printing pressure is maintained for multipart paper. Moving the adjusting cam toward the left or right adjusts the guide rail up or down. Figure 2-5 Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 16 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.4 Ribbon Drive (See Figure 2-6 below). The ribbon driver mechanism moves the ribbon in synchronization with the space motor operation. The ribbon drive mechanism consist of the following items: (a) Ribbon drive gear assembly (b) Ribbon gear (space motor) (c) Ribbon cartridge (1) Ribbon cartridge An endless ribbon with a single direction feed is used. Ink is supplied from an ink reservoir, which is built in to the ribbon cartridge. (2) Ribbon feed operation When the space motor is activated, the ribbon gear rotates. The rotation is transmitted via the ribbon drive gear assembly to the drive gear in the ribbon cartridge, thus moving the ribbon. The feed direction of the ribbon is maintained by switching the direction of the gears in the ribbon drive gear assembly. This ensures ribbon movement when bi-directional printing is used. Figure 2-6 Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 17 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.5 Paper Feed Operation Paper is fed by turning the platen and the pin tractor, which is driven by the LF pulse motor. The paper feed mechanism consists of the following: (a) Pulse motor with gears (b) Decelerating gear (c) Platen (d) Tractor feed unit (e) Pressure roller (1) Cut sheet and continuous sheet switching mechanism (See Figure 2-8.) Three different paper paths can be selected and set by the change lever. (a) TOP (for cut sheets) When the cut sheet paper is used in the manual mode or fed by the CSF (option), set the change lever at the position marked TOP. Operation The driving force of the platen gear (R) is transmitted to the idle gear by setting the change lever to the TOP position. However, this causes the idle gear to be disengaged from the change gear, leaving it free. At this time, the pressure rollers (at the rear and the front) are pressed securely to the platen to feed the sheet. At the same time, he cut sheet detection lever turns on the cut sheet detection switch, to confirm to the control board that you are in the cut sheet mode. In the cut sheet mode, the control board automatically feeds the sheet up to the print start position after pausing for the wait time stored in the menu. (b) REAR (Continuous sheet from push tractor) When the change lever is set to REAR position, the change gear is engaged with the idle gear and the tractor gear to transmit the rotation of the platen to the push tractor shaft, and the paper is fed from the push tractor. At the same time, the switch lever turns on the rear switch, to inform the control board that you are in the continuous sheet mode. (c) BOTTOM (Continuous sheet from bottom feeder) (option) When the change lever is set in the BOTTOM position, the rotation of the platen is transmitted to the drive gear of the bottom tractor feed unit through the idle gear to feed the sheet which set in the bottom tractor feed. At the same time, the switch lever turns on the bottom switch to inform the control board that you are in the continuous sheet mode. (2) Cut-sheet feeder operation (See Figure 2-9.) The pulse motor used for the paper feed mechanism is mounted on the left of the frame, and the rotation of the motor is transmitted through decelerating gears (LF idle gear, platen gear) to the platen. When using cut-sheet paper, the change lever must be in the TOP position to grab the paper, while disengaging the push tractor. When the change lever is set to the TOP position, the paper is automatically fed in up to the print start position after pausing for the wait time stored in the menu. (3) Continuous paper feed operation (Rear) (See Figure 2-10.) The force transmitted to the platen turns the tractor gear by means of the platen gear, the idler gear, and the change gear. The rotation of the tractor gear turns the sheet feeder shaft, which moves the pin tractor belt, feeding the paper. (4) Pull tractor (option) and push tractor operation (See Figure 2-11) This mechanism supports the standard push tractor and an optional pull tractor. It can perform forward and reverse feed by sending paper either to the push tractor (for rear feed) or to the pull tractor (for bottom feed). The rotation of the platen is transmitted to the push tractor and the pull tractor. Paper can be fed to either tractor. (5) Pull tractor mechanism (option) (See Figure 2-12.) Bottom feed of continuous sheets is possible only when the optional pull tractor unit is installed. The rotation of the platen is transmitted to the idle gear of the pull tractor unit through the platen gear at the left end of the platen. The rotation of the idle gear is transmitted to the drive gear, and paper is fed when the sheet feeder shaft turns the pull tractor. (6) Bottom push feed operation (Option) (See Figure 2-13.) The bottom push feed of continuous sheet requires the bottom tractor feed unit. When the platen turns, its rotational force is transmitted through the tractor idle gear and the tractor change gear to the tractor drive gear of the bottom push tractor, and paper is fed to the print start position. (7) Paper clamp mechanism (See Figure 2-14.) When setting the change lever to the BOTTOM , TOP or REAR position, the operation of the front release gear arm changes according to the position of the release cam. At the same time, the position of the cam relative to the front release gear arm changes, opening or closing the pressure roller. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 18 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.6 Paper Detection Mechanism (See Figure 2-15 below). (1) Cut sheet detection When the sheet is inserted, point A is pushed backward and the paper near end lever B rotates counterclockwise (CCW). At this time, the rear sensor lever rotates counterclockwise (CCW) and pulls out of the rear and top paper end sensor to detect that the sheet is inserted. The procedure for the paper end is the reverse, that is, detection occurs when the paper end sensor is blocked. (2) Rear feed detection When the sheet is fed from the push tractor, the point B is pushed to the front side and the paper near end lever A rotates clockwise (CW). At this time, the rear sensor lever rotates counterclockwise (CCW), and pulls out of the rear and top paper end sensor to detect that the sheet is provided. The procedure for the paper end is the reverse, that is, detection occurs when the rear sensor lever interrupts the sensor. (3) Bottom feed detection When the sheet is fed from the bottom, the point C rotates clockwise (CW). When the bottom sensor lever rotates clockwise (CW), it pulls out of the bottom paper end sensor to detect that the sheet is inserted. The procedure for the paper end is the reverse, that is, detection occurs when the bottom sensor lever interrupts the sensor. (4) Top line print mechanism (See Figure 2-16.) The top edge of the sheet is protected by the ribbon protector so that it can stop at a position very close to the printhead (0 tear-off position) to start printing at the top of the sheet without causing it to crumple or curl up. Printing starts at the top of the sheet, and continues uni-directionally until the top edge of the sheet gets to the inside of the pull-up roller cover. After that, printing continues bi-directionally. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 19 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.7 Automatic Sheet Feed This function is used to feed in the sheet automatically up to the print start position when the cut sheet or the continuous sheet paper is used. Operational procedure (1) When using cut sheet paper: 1) Set the change lever to the TOP position. (See Figure 2-17 below). 2) Insert a sheet of paper between the platen and the paper chute. 3) After the lapse of time selected by the "wait time" item in the menu, the LF motor starts to feed the paper up to the print position. 4) When the default is selected, the paper feeds up to the position 0.35 inches (first dot position) from the top edge of the sheet. However, the 0 tear-off mechanism allows printing at the top edge of the sheet by changing the TOF position. (2) When using continuos sheet paper 1) Set the change lever either to the rear or the bottom position. (See Figure 2-17 above). 2) Load paper either on the push tractor or on the bottom tractor. 3) Press the "FF/LOAD" button. 4) The LF motor starts to feed the paper up to the print start position. 5) The paper feeds up to the TOF position (Factory default: 0.35 inches from the top). Press the "FF/LOAD" button. When the LF motor completes its operation and the sheet has not been fed in, an alarm condition results. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 20 Service Guide ML320/321Turbo Chapter 2 Operation Description 2.2.8 Paper Park Function (Continuous sheet paper) Continuous sheet paper can be backed out automatically by using the "PARK" button on the operation panel. 1) Press the "PARK" button. 2) Reverse LF starts and paper feeds in reverse until paper end occurs or a maximum of 19 inches have been fed. 3) The paper feeds in reverse to leave the paper on the tractor. The alarm LED lights up when paper end is not detected after 19 inches of reverse feeding. The operator can press the SEL button to turn off the alarm LED, then press the PARK button to continue the park function. This operation is required when the paper to be parked is more than 19 inches long. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 21 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3. ASSEMBLY/DISASSEMBLY This section explains the procedures for removing and installing various assemblies and units in the field. Description is mainly limited to the removal procedure; installation should basically be performed in the reverse sequence of the removal procedure. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 22 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.1 Precautions for Parts Replacement (1) Remove the AC power cord and the interface cable before disassembling or assembling. (a) Turn off the power switch. Remove the plug of the AC power cord from the outlet. Remove the power cord from the receptacle on the printer. (b) To reconnect the power cord, connect it to the receptacle on the printer first, thenplug it into the outlet. (2) Do not disassemble the printer as long as it is operating normally. (3) Do not remove unnecessary parts, and limit the extent of disassembly as much as possible. (4) Use the designated service tools. (5) Carry out disassembly in the prescribed sequence; otherwise, damage to the parts may result. (6) It is advisable to temporarily install screws, snap rings and other small parts in their original positions to avoid losing them. (7) Whenever handling the microprocessors, ROM, RAM IC chips and boards, do not use gloves that may cause static electricity. (8) Do not place the printed circuit board directly on the equipment or on the floor. (9) If adjustment is specified in the middle of installation, follow the instructions. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 23 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.2 Service Tools Table 3.1 lists the tools necessary for replacing printed circuit boards and parts of units in the field. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 24 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3 Disassembly/Reassembly Procedure This section explains the assembly replacement procedures according to the following disassembly system. Parts Layout How to Change Parts This section explains how to change parts and assemblies appearing in the disassembly diagram below. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 25 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.1 Printhead (1) Open the access cover. (2) Pull up and rotate the head clamp 1 to unclamp the printhead 2 as shown in fig. 3.3.1. (3) Disconnect the printhead 2 from PC connector 3 and remove. (4) To install, reverse the removal steps. Notes on installation: (1) Insert the printhead 2 into the PC connector 3 while pushing it against the carriage frame 4. (2) The head clamp 1 must be securely sandwiched between printhead 2 and carriage frame 4 as shown in fig. 3.3.2 below. (3) Be sure to check the gap between platen and printhead (see 4). (4) Be careful not to touch the print head while it is hot. Important: There is a shim on the carriage frame 4, which hangs over the platen side of the frame. Be sure to replace it correctly. Improper positioning of this shim will severely affect the printhead gap. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 26 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.2 Ribbon Protector (1) Remove the printhead (see 3.3.1 below). (2) Open the pull-up roller cover 1. (3) Remove the shim on the carriage frame. (4) Loosen the screws holding the carriage assembly to the carriage frame--this allows more play between the printhead and the platen. (5) Raise and remove the ribbon protector 2. (6) To install, follow the removal steps in reverse order. Be sure to replace the shim in exactly the same position as it was before disassembly. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 27 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.3 Pull-up Roller Assy (1) Open the access cover 1. (2) Lift up the sheet guide Assy 4 to remove. (3) Tilting the pull-up roller Assy 2 toward the front, remove it from the shaft of platen Assy 3. (4) To install, follow the removal steps in reverse order. Note: Remove the sheet guide Assy 4 before installing or removing the pull-up roller Assy 2. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 28 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.4 Upper Cover Assy, Access Cover Assy and Sheet Guide Assy (1) Pull off the platen knob 1. (2) Open the access cover Assy 4 toward the front to remove. (3) Lift up the sheet guide Assy 5 to remove. (4) Turn the change lever 2 toward the bottom position. (5) Insert a flat-blade screwdriver into grooves of frame (5 places for ML 321, 4 places for ML320) and twist to disengage claws of upper cover 3. (6) Raise the front side of upper cover Assy 3 and shift toward the rear to disengage claws of frame (6 places for ML321, 5 places for ML320). (7) Raise the upper cover Assy 3 to remove. (8) To install, follow the removal steps in reverse order. Note on installation: Match the posts A at both sides of the sheet guide 5 with the arrow marks on the upper cover. Push the guide into the cover. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 29 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.5 Gear Case Assy (1) Remove the printhead (see 3.3.1 ). (2) Remove the shim from the carriage frame. (3) Remove the upper cover (see 3.3.4 ). (4) Move the carriage Assy to right side, remove two screws 1, then remove the carriage Assy. (5) Disengage claws on the gear Assy (4 places). Using a flat-blade screwdriver, push to widen the claw for easy disengagement. (6) Lift up the gear case Assy 3 and release the carriage cable from the cable clamp of the gear case Assy. (7) To install, follow the removal steps in reverse order. Be sure to replace the shim on the carriage frame in exactly the same position as it was before disassembly Notes on installation: (1) To assemble, align the direction of the SP motor axis 4 with the Gear Hole of the Gear Case assy. (2) Be sure to check and adjust the gap between platen and printhead (see 4-1 ). Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com)

Page: 30 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.6 PC Connector (1) Remove the upper cover (see 3.3.4 ). (2) Remove the printhead (see 3.3.1 ). (3) Remove the shim from the carriage frame. (4) Remove the gear case Assy (see 3.3.5 ). (5) Remove the PC connector 1 from the space motor Assy 2. (6) To install, follow the removal steps in reverse order. Be sure to replace the shim on the carriage frame in exactly the same position as it was before disassembly Notes on installation: (1) Do not touch the space motor 2 or terminals of PC connector 1. Also, take care to avoid dust or foreign matter. (2) After installation, check and adjust the gap between platen and printhead (see 4-1 ). Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business

Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 31 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.7 Space Motor, Guide Roller Assy (1) Remove the printhead (see 3.3.1 ). (2) Remove the upper cover (see 3.3.4 ). (3) Remove the gear case Assy (see 3.3.5 ). (4) Remove the PC connector (see 3.3.6 ). (5) Remove screw 2, then the guide roller Assy 3 from the space motor Assy 1. (6) Push down on the carriage cable and remove it. (7) Remove the two screws 5, from the space motor Assy. (8) Remove the space motor. (9) To install, follow the removal steps in reverse order. Notes on installation: (1) Do not touch the terminals of space motor 1. Also, take care to avoid dust or foreign matter. (2) When installing the guide roller Assy 3, push portions A and B against the space motor 1. (3) When installing the space motor 1, align the face C with carriage frame 4 and push portionD against the frame. (4) After installation, check and adjust the gap between platen and printhead (see 4-1 ). Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 32 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.8 Space Rack (1) Remove the upper cover (see 3.3.4 ). (2) Remove the printhead (see 3.3.1 ). (3) Remove the shim from the carriage frame. (4) Remove the gear case Assy (see 3.3.5 ). (5) Remove the space motor Assy (see 3.3.7 ). (6) Remove the spring 1. (7) Disengage the claw on left side of space rack 2 from the frame, and remove the space rack 2 in upper direction. (8) To install, follow the removal steps in reverse order. Be sure to replace the shim on the carriage frame in exactly the same position as it was before disassembly Note on installation: After installation, check and adjust the gap between platen and printhead (see 4-1 ). Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 33 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.9 Carriage Cable (1) Remove the upper cover (see 3.3.4 ). (2) Remove the printhead (see 3.3.1 ). (3) Remove the shim from the carriage frame. (4) Remove the gear case Assy (see 3.3.5 ). (5) Remove the space motor Assy (see 3.3.7 ). (6) Remove the two screws 1, release the driver board 2 and PCB board 9 by lifting clamp 8, and disconnect cable from connector 3, 4, 5, 6. (7) Remove the carriage cable 7 from fasteners on frame. (8) To install, follow the removal steps in reverse order. Be sure to replace the shim on the carriage frame in exactly the same position as it was before disassembly Notes on installation: (1) Take care not to fold the carriage cable 7 during installation. Curve the carriage cable 7 slightly when assembling into the fasteners. (2) Make sure that the paper end lever A will not contact the paper end sensor 10 when installing the driver board. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 34 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.10 Backup Roller Holder Assy (1) Remove the upper cover (see 3.3.4). (2) Remove the printhead (see 3.3.1). (3) Remove the carriage Assy (see 3.3.5 (3)). (4) Remove the backup roller spring 2. Disengage claws of roller holder from the carriage frame 1 (2 places), and remove thebackup roller holder assy 3. (6) To install, follow the removal steps in reverse order. Note: Small round hole with metal tip on back of roller holder assy 3 should be facingup when installing. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 35 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.11 Platen Assy (1) Remove the printhead (see 3.3.1 ). (2) Remove the upper cover (see 3.3.1 ). (3) Remove the pull-up roller Assy (see 3.3.3 ). (4) Remove the ribbon protector (see 3.3.2 ). (5) Turn the change lever 1 to the bottom position. (6) Push in the lock levers 2 on both sides to unlock the Assy from the frame, then rotate them upward 90°. (7) Remove the platen Assy 4 from the base frame. (8) To install, follow the removal steps in reverse order. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 36 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.12 Driver Board (SDDV) (1) Remove the upper cover (see 3.3.4 ). (2) Remove the two screws 1, and release the driver board 2 by lifting clamp 4. (3) Disconnect all cables from driver board 2. (4) To install, follow the removal steps in reverse order. Note on installation: Insert sensor lever 3 in the sensor as shown when installing the driver board 2. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 37 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.13 LF Motor (1) Remove the upper cover (see 3.3.4 ). (2) Remove the printhead (see 3.3.1 ). (3) Remove the ribbon protector (see 3.3.2 ). (4) Remove the pull-up roller Assy (see 3.3.3 ). (5) Remove the platen Assy (see 3.3.11 ). (6) Remove the driver board (see 3.3.12 ). (7) Remove the left FG plate 1: lift base at three points to release tabs. (8) Release the lock A to remove the LF motor 2. (9) To install, follow the removal steps in reverse order. Note on installation: Press the LF motor cable with a portion A of the motor plate. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 38 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.14 Operation Panel PCB (LEOP) (1) Remove the upper cover (see 3.3.4 ). (2) Disconnect cable 1 from connector 3 of driver board 2. (3) Disengage claws on both sides from the frame, and remove the operation panel 4. (4) Open claws (8 places) and remove the operation panel PCB 5 from the operation panel 4 . (5) To install, follow the removal steps in reverse order. Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business Partner Exchange (BPX) for any updates to this material. ( bpx.okidata.com) Page: 39 Service Guide ML320/321Turbo Chapter 3 Parts Replacement 3.3.15 Control/Power Supply Board (SDCT) (1) Remove the upper cover (see 3.3.4 ). (2) Disconnect the two flexible cables 3 from connector 2 on the Control/Power Supply Board 1. (3) Remove cable 5 from connector 4 on the control/power supply board 1. (4) Remove the two screws 6, and remove the control power supply board 1. (5) To install, follow the removal steps in reverse order. Note on installation: To install the control/power supply board, set the change lever to the top position so that the switch lever 7 will not catch on the microswitches 8.


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