Oki ML421 Maintenance Manual

Oki ML421 Manual

Get Oki ML421 PDF manuals and user guides View all Oki ML421 manuals
Add to My Manuals
Save this manual to your list of manuals

Oki ML421 manual content summary:

  • Oki ML421 | Maintenance Manual - Page 1
    Oki Data CONFIDENTIAL ML420/421 PRINTER Maintenance Manual ODA 42113901 Rev.2 1 / 133
  • Oki ML421 | Maintenance Manual - Page 2
    Oki Data CONFIDENTIAL 42113901 Rev.2 2 /
  • Oki ML421 | Maintenance Manual - Page 3
    PREFACE Oki Data CONFIDENTIAL This maintenance manual describes how to maintain the ML420/421 printer in the field. This manual is for customer engineers. For further information, refer to the Users Manual for handling or operating the equipment. The relation between the destination point and the
  • Oki ML421 | Maintenance Manual - Page 4
    Oki Data CONFIDENTIAL Contents 1. CONFIGURATION 6 1.1 Standard Printer Printhead Mechanism and Operation 31 2.2.2 Spacing Operation 34 2.2.3 Head Gap Adjusting 35 2.2.4 Ribbon Parts Replacement 53 3.2 Service Tools ...54 3.3 Disassembly/Reassembly Procedure 55 3.3.1 Printhead ...57 3.3.2 Ribbon
  • Oki ML421 | Maintenance Manual - Page 5
    95 6.1 Items to Check Before Repair 95 6.2 Troubleshooting Table ...95 6.3 Lamp Display ...96 6.4 Connection Circuit Check for Printhead and SP/LF Motor 100 6.5 Troubleshooting flow chart 102 APPENDIX A PCB LAYOUT 114 APPENDIX B SPARE PARTS LIST 115 APPENDIX C RS-232C SERIAL INTERFACE BOARD
  • Oki ML421 | Maintenance Manual - Page 6
    1. CONFIGURATION 1.1 Standard Printer Configuration This printer consists of the following assemblies: Sheet guide assy Platen knob Oki Data CONFIDENTIAL Access cover assy Upper cover Transformer assy Power supply board Pull-up roller assy Control board Operation panel assy Main chassis
  • Oki ML421 | Maintenance Manual - Page 7
    1.2 Options (1) Cut sheet feeder unit (CSF) (Narrow and wide versions available) Dual-bin CSF Oki Data CONFIDENTIAL Single-bin CSF Attachment assy Attachment assy (2) Pull-tractor assy 42113901 Rev.2 7 /
  • Oki ML421 | Maintenance Manual - Page 8
    (3) Bottom push tractor unit Oki Data CONFIDENTIAL (4) Roll paper stand (Narrow only) (5) RS232C Serial interface board 42113901 Rev.2 8 /
  • Oki ML421 | Maintenance Manual - Page 9
    Oki Data CONFIDENTIAL 2. THEORY OF OPERATION 2.1 Electrical Operation The electrical operation of the printer circuit is described in this section. 2.1.1 Summary Figure 2-1 shows the block diagram of the printer the entire printer by executing the control program through the LSI and driver circuits.
  • Oki ML421 | Maintenance Manual - Page 10
    12 volt 5 volt Divider Converter USB Controller LSI USB I/F (opt.) CSF (opt.) Roll paper stand ParaI/F HTEMP Head driver (opt.) Serial- I/F HEAD HD alarm HEADGAP HEADGAP-SW Photo sensor SP/LF driver M SP Thermister SPTEMP M LF RESET 5VD POWLEV HTEMP Fuse 42 V 42V -8V 3.3V 5VS Figure
  • Oki ML421 | Maintenance Manual - Page 11
    Oki Data CONFIDENTIAL (2) Program ROM This is a 256 × 16 bits (4M bit) EPROM or MASK ROMwith 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-N signal of the
  • Oki ML421 | Maintenance Manual - Page 12
    Oki Data CONFIDENTIAL (3) RAM The RAM is CMOS dynamic RAM with 256K × 16-bit (4Mbit), and used as buffers (such T4 A0~A8 RAS-N VCAS-N LCAS-N RD-N D0~D15 (Read) WR-N D0~D7 (Write) 16-bit bus, Word instruction * Clockout is provided when the original excitation is selected. 42113901 Rev.2 12 /
  • Oki ML421 | Maintenance Manual - Page 13
    (4) USB Controller The USB Controller detects and controls the USB interfacee. The following shows the USB Controller access operation. Oki Data CONFIDENTIAL MPU PP0O2 2 RD PWSRELN Clockout * A0~A7 USBCS-N RD-N A0~A7 D0~D7 USBCS-N RD-N WRL-N USB Controller CE RD WR D0~D7 (Read)
  • Oki ML421 | Maintenance Manual - Page 14
    Oki Data CONFIDENTIAL (5) 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. MPU P24 P27 P25 P26 EEDIN-P EECS-P EEDOUT-P EECLK-P EEPROM D1 CS DO SK
  • Oki ML421 | Maintenance Manual - Page 15
    Oki Data CONFIDENTIAL (6) LSI This LSI detects and controls the SP motor speeds by monitoring the two RAS 0 RAS-N Clockout* A0~A19 LSICS-N ALE D0~D7 (Read) RD-N D0~D7 (Write) WRL-N Address Address Data Data * Clockout is provided when the original excitation is selected. 42113901 Rev.2 15 /
  • Oki ML421 | Maintenance Manual - Page 16
    Oki Data CONFIDENTIAL 2.1.3 Initialization This printer is initialized when the power is turned on or Reset operation by I-PRIME starts program to initialize, but does not reset the MPU. The program here sets the mode of the LSI including the MPU, checks the memories (ROMs and RAMs), then carries
  • Oki ML421 | Maintenance Manual - Page 17
    Oki Data CONFIDENTIAL 2.1.4 Interface Control (1) Parallel Interface 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
  • Oki ML421 | Maintenance Manual - Page 18
    Oki Data CONFIDENTIAL (2) Universal Serial Bus (USB) Universal Serial Bus Specification Revision 1.0 compliance. 1) Connector • Printer Side • Cable Side : Black Drain Wire 4) Connector pin arrangement 2 1 3 4 5) Mode & Class of Device • Full - speed Driver • Self - powered Device 6) Data
  • Oki ML421 | Maintenance Manual - Page 19
    Oki Data CONFIDENTIAL 9) Signal Level • Input / Output Level Parameter Symbol Min. Input Levels : High (driven) VIH 2.0 High (floating) VIHZ 2.7 Low VIL Output Levels : Low OL 0.0 High (driven)
  • Oki ML421 | Maintenance Manual - Page 20
    Oki Data CONFIDENTIAL 2.1.5 Print Control Print data is transmitted as parallel data (HEAD1~HEAD9) from LSI to print head. LSI generates print timing and drive time. Control Board MPU LSI A/D bus Print Data DRIVER Print Data Print Head HEAD1-N~ HEAD9-N HEAD1~ HEAD9 HEAD DRIVE TIMING CHART
  • Oki ML421 | Maintenance Manual - Page 21
    Oki Data CONFIDENTIAL Print Compensation Control The print compensation can be made as shown below: (a) Voltage compensation (See 2.1.8 "Alarm Circuit.") (b) Temperature compensation (See 2.1.8 "Alarm Circuit.") (c) Pin stroke compensation Platen Pin 1,2 3~6 8,9 Print Head below: Head Gap Range
  • Oki ML421 | Maintenance Manual - Page 22
    Oki Data CONFIDENTIAL 2.1.6 SP/LF Motor Control The MPU transmits serially the SP motor data and the LF motor control data too the SP/LF motor driver, according to the commands sent from the MPU. LSI MPU φA/φB P23 SPU SPV SPW SLATCH-N P20 SDATA-N P22 SCLK-N MHM2025 SPU SPV SPW SP Decoder
  • Oki ML421 | Maintenance Manual - Page 23
    Oki Data CONFIDENTIAL (1) Space motor control The SP motor driver (MHM2025) drives the three-phase brushless motor based on the phase signal (SPU, SPV and SPW) from the LSI and the speed instruction data from the MPU. The MPU can identify the current speed of the space motor by measuring through the
  • Oki ML421 | Maintenance Manual - Page 24
    Oki Data CONFIDENTIAL (2) Encoder disk In the operation of the spacing motor, (3) LF motor control The LF motor driver (MHM2025) 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 MPU. The data from the MPU is processed by a
  • Oki ML421 | Maintenance Manual - Page 25
    panel control IC. LSI OPTD OPCK NPA2 OPRD OPTXD 48 OPCLK 47 OPCLR-N 45 OPRXD 46 Operation panel control IC Command and Data latch LED driver +5V Switch controller A 2-byte (15 bits + 1 even parity bit) command (OPTXD) is transmitted to the Operation panel control IC in synchronization with
  • Oki ML421 | Maintenance Manual - Page 26
    for OK or NG 4 NO YES Error notification 7 5 Instruction for 6 retransmission 8 2 3 bit0 bit7 Command (first) 2 Command (second) 6 3 1 5 or 8 7 bit0 bit7 Command response (first) Note Command response (second) Oki Data CONFIDENTIAL Note: From the illustration above, you can
  • Oki ML421 | Maintenance Manual - Page 27
    Oki Data CONFIDENTIAL 2.1.8 Alarm Circuit (1) AC fuse open alarm (a) Head drive time alarm circuit This control the drive time and the print speed (pass number) of the head. 50V R542 POWLEV R541 (a) Head drive time The head drive time is lengthened to compensate for the amount of voltage drop by
  • Oki ML421 | Maintenance Manual - Page 28
    Oki Data CONFIDENTIAL (4) Overheat alarm (a) Head overheat alarm The voltage of the output HTEMP signal of the thermistors, one of which is contained in the print head and the other in the SP/LF driver, is monitored by the A/D port of the MPU to control the voltage. Temp Stop Mode up 125°C 118°C
  • Oki ML421 | Maintenance Manual - Page 29
    Oki Data CONFIDENTIAL (b) SP motor overheat alarm The voltage of the output SPTEMP signal of the thermistors, one of which is contained in the SP Motor, is
  • Oki ML421 | Maintenance Manual - Page 30
    Oki Data CONFIDENTIAL 2.1.9 Power Supply Circuit This power supply circuit supplies the +3.3VDC, +5VDC, +12VDC, +42VDC, +50VDC, drive Logic IC / LED drive Serial interface line, FAN motor drive LF motor / SP motor drive Printhead, Option CSF motor drive Serial interface line 42113901 Rev.2 30 /
  • Oki ML421 | Maintenance Manual - Page 31
    Oki Data CONFIDENTIAL 2.2 Mechanical Operation 2.2.1 Printhead Mechanism and Operation (See Figure 2-2.) The printhead is a spring charged 9-pin driving head Head Pins View from the Tip of the Printhead (1) The printhead configuration: The printhead is composed of the following parts: (a) Wire guide
  • Oki ML421 | Maintenance Manual - Page 32
    Oki Data CONFIDENTIAL (2) Operation of printhead (See Figure 2-3.) (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
  • Oki ML421 | Maintenance Manual - Page 33
    Paper Print wire Oki Data CONFIDENTIAL Printhead Platen (1) When printing Paper Armature assembly Print wire Thermistor (2) When not printing Paper Wire guide Yoke Magnet assembly Spacer 42113901 Rev.2 Figure 2-3 33 /
  • Oki ML421 | Maintenance Manual - Page 34
    Oki Data CONFIDENTIAL 2.2.2 Spacing driver board included) (c) Carriage shaft (d) Space rack (e) Sensor (f) Encoder disk (1) Spacing operation The carriage frame, on which the printhead detected by the sensor. Printhead Carriage shaft Carriage frame Space rack Encoder disk Encoder sensor
  • Oki ML421 | Maintenance Manual - Page 35
    Oki Data CONFIDENTIAL 2.2.3 Head Gap Adjusting (See Figure 2-5.) The head gap adjusting lever moves back and forth to tilt the carriage frame, altering the gap between the printhead can be turned with a screw driver to change the coarse gap adjustment. When the adjusting lever is set to range 2 ~ 5
  • Oki ML421 | Maintenance Manual - Page 36
    Platen Oki Data CONFIDENTIAL Range 1 2 3 4 5 Carriage shaft Printhead Adjusting lever Adjusting screw Adjusting gear Idler gear Range from 5 to 1 Adjusting screw Adjusting cam C.C.W. Narrows Printhead Platen Range from 1 to 5 Guide rail C.W. Widens 42113901 Rev.2 Figure 2-5 36 /
  • Oki ML421 | Maintenance Manual - Page 37
    Oki Data CONFIDENTIAL 2.2.4 Ribbon Drive (See Figure 2-6.) 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)
  • Oki ML421 | Maintenance Manual - Page 38
    Oki Data CONFIDENTIAL 2.2.5 Paper Feed Operation Feeding of the paper is performed by turning the platen and the pin tractor, which is driven by the LF pulse
  • Oki ML421 | Maintenance Manual - Page 39
    Oki Data CONFIDENTIAL (1) Cut sheet and continuous sheet switching mechanism (See Figure 2-7.) Three different paper paths can be selected and set by the change lever. (a) TOP (for cut sheet) When the cut sheet is used in the manual mode or fed by the CSF (option), set the change lever at the
  • Oki ML421 | Maintenance Manual - Page 40
    Oki Data CONFIDENTIAL Control Power supply Assy Switch lever Bottom switch Change gear shaft Rear switch Change lever Release shaft Change arm TOP Platen REAR BOTTOM Change
  • Oki ML421 | Maintenance Manual - Page 41
    Oki Data CONFIDENTIAL (2) Cut-sheet feeder operation (See Figure 2-8.) The pulse motor used for in the TOP position to grab the paper, while disengaging the push tractor. When the change lever is set to the TOP position, the cut sheet is automatically fed in up to the print start position after
  • Oki ML421 | Maintenance Manual - Page 42
    Oki Data CONFIDENTIAL (3) Continuous paper feed operation (Rear) (See Figure 2-9.) The force transmitted to the platen, rotates the tractor gear through platen gear, the idler gear and
  • Oki ML421 | Maintenance Manual - Page 43
    Oki Data CONFIDENTIAL (4) Push and pull tractor mechanism (Option) (See Figure 2-10). This mechanism consist of an optional pull tractor and a standard push tractor mechanism. This mechanism can perform forward and reverse feed by setting continuous sheets to the push tractor and pull tractor. The
  • Oki ML421 | Maintenance Manual - Page 44
    Oki Data CONFIDENTIAL (5) Pull tractor mechanism (option) (See Figure 2-11.) Bottom feed of continuous sheets is possible only when an optional pull tractor unit is installed. The
  • Oki ML421 | Maintenance Manual - Page 45
    Oki Data CONFIDENTIAL (6) Bottom push feed operation (Option) (See Figure 2-12.) The bottom push feed of the continuous sheet is possible only when the bottom tractor feed
  • Oki ML421 | Maintenance Manual - Page 46
    Oki Data CONFIDENTIAL (7) Paper clamp mechanism (See Figure 2-13.) 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
  • Oki ML421 | Maintenance Manual - Page 47
    TOP Release cam Platen Change lever Oki Data CONFIDENTIAL BOTTOM Front release gear arm REAR 42113901 Rev.2 Figure 2-13 47 /
  • Oki ML421 | Maintenance Manual - Page 48
    Oki Data CONFIDENTIAL 2.2.6 Paper Detection Mechanism (See Figure 2-14.) (1) Cut sheet detection When the cut sheet is inserted, the point A is pushed backward and the paper near
  • Oki ML421 | Maintenance Manual - Page 49
    Oki Data CONFIDENTIAL (4) Top line print mechanism (See Figure 2-15.) The front edge of the sheet is protected by the ribbon protector so that it can stop at a position just near to the print head . Platen Ribbon protector Printhead Carriage frame assembly Figure 2-15 42113901 Rev.2 49 /
  • Oki ML421 | Maintenance Manual - Page 50
    Oki Data CONFIDENTIAL 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 is used. [Operational procedure] (1) When using the cut sheet 1) Set changing the TOF position. Sheet setting Time out
  • Oki ML421 | Maintenance Manual - Page 51
    Oki Data CONFIDENTIAL (2) When using the continouos paper 1) Set the change lever either to the rear side or the bottom side position. (See Figure 2-16.) 2) Set a sheet of paper either to the push tractor or the bottom tractor. 3) Press the "FF/LOAD" switch. 4) The LF motor starts its operation to
  • Oki ML421 | Maintenance Manual - Page 52
    Oki Data CONFIDENTIAL 2.2.8 Paper Park Function (Continuous paper) Continuous sheets which have been inserted can be reversed automatically by using the "PARK" button on the operation panel. 1)
  • Oki ML421 | Maintenance Manual - Page 53
    Oki Data CONFIDENTIAL 3. ASSEMBLY/DISASSEMBLY This section printer as long as it is operating normally. (3) Do not remove unnecessary parts, and limit the disassembly area as much as possible. (4) Use the designated service the middle of installation, follow the instructions. 42113901 Rev.2 53 /
  • Oki ML421 | Maintenance Manual - Page 54
    Oki Data CONFIDENTIAL 3.2 Service Tools Table 3.1 lists the tools necessary for replacing printed circuit boards and parts of units in the field. Table 3.1 Service tools No. Service Tool Q'ty Use Remarks 1 No. 1-100 Phillips screwdriver 1 Screws 2.6 mm 2 No. 2-200 Phillips screwdriver
  • Oki ML421 | Maintenance Manual - Page 55
    Oki Data CONFIDENTIAL 3.3 Disassembly/Reassembly Procedure This section explains the assembly replacement procedures according to the following disassembly system. [Parts Layout] Upper cover assy Transformer assy Power supply board Printhead Control board Printer unit Operation panel board
  • Oki ML421 | Maintenance Manual - Page 56
    Oki Data CONFIDENTIAL [How to Change Parts] This section explains how to change parts and assemblies appearing in the disassembly diagram below. Printer unit 3.3.1 Printhead 3.3.2 Ribbon protector 3.3.3 Pull-up roller assy 3.3.4 Upper cover, access cover and sheet guide 3.3.5 Gear case assy 3.3.6
  • Oki ML421 | Maintenance Manual - Page 57
    Oki Data CONFIDENTIAL 3.3.1 Printhead (1) Open the access over. (2) Pull up and rotate the head clamp 1 to unclamp the printhead 2 as shown fig. 3.3.1. (3) Disconnect the printhead 2 from PC connector 3. (4) To install, follow the removal steps in the reverse order. Notes on installation: (1)
  • Oki ML421 | Maintenance Manual - Page 58
    3.3.2 Ribbon Protector (1) Remove the printhead (see 3.3.1). (2) Open the pull-up roller cover 1. (3) Raise and remove the ribbon protector 2. (4) To install, follow the removal steps in the reverse order. 2 Oki Data CONFIDENTIAL 1 42113901 Rev.2 58 /
  • Oki ML421 | Maintenance Manual - Page 59
    Oki Data CONFIDENTIAL 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 from the shaft of platen Assy 3. (4) To install, follow the removal steps
  • Oki ML421 | Maintenance Manual - Page 60
    Oki Data CONFIDENTIAL 3.3.4 Upper Cover Assy, Access Cover Assy and Sheet Guide Assy (1) Pull off the platen knob 1. (2) (6) Open the access cover Assy 4 toward the front to remove. (7) Lift up the sheet guide Assy 5 to remove. (8) To install, follow the removal steps in the reverse order. Remark on
  • Oki ML421 | Maintenance Manual - Page 61
    Oki Data CONFIDENTIAL 3.3.5 Gear Case Assy (1) Remove the printhead (see 3.31). (2) Remove the upper cover (see 3.3.4 (1) - (5)). (3) Move the carriage Assy to right hand side, remove two screws 1, then the space motor 2. (4) Disconnect a carriage cable. (5)
  • Oki ML421 | Maintenance Manual - Page 62
    Oki Data CONFIDENTIAL 3.3.6 PC Connector (1) Remove the printhead (see 3.3.1). (2) Remove the upper cover (see 3.3.4 (1) - (5)). dust or foreign matters. (2) After installation, check and adjust the gap between platen and printhead (see 4-1). (3) Make sure that there is not any dust or oil on the
  • Oki ML421 | Maintenance Manual - Page 63
    Oki Data CONFIDENTIAL 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 (1) - (5)). (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
  • Oki ML421 | Maintenance Manual - Page 64
    Oki Data CONFIDENTIAL 3.3.8 Space Rack (1) Remove the printhead (see 3.3.1). (2) Remove the upper cover (see 3.3.4 (1) - (5)). (3) Remove the gear case Assy (see 3.3.5). (4) Remove the space motor (see 3.3.7). (5) Remove the spring 1. (6) Disengage the claw on left
  • Oki ML421 | Maintenance Manual - Page 65
    Oki Data CONFIDENTIAL 3.3.9 Carriage Cable (1) Remove the printhead (see 3.3.1). (2) Remove the upper cover (see 3.3.4 (1) - (5)). (3) Remove the gear case Assy (see 3.3.5). (4) Remove the space motor (see 3.3.7). (5) Remove the space rack (3.3.8). (6) Remove two screws 1, release
  • Oki ML421 | Maintenance Manual - Page 66
    Oki Data CONFIDENTIAL 3.3.10 Backup Roller Holder Assy (1) Remove the printhead (see 3.3.1), (2) Remove the upper cover (see 3.3.4 (1) - (5)). (3) Remove the gear case Assy (see 3.3.5). (4) Remove the space motor (see 3.3.7). (5) Remove the backup roller spring 2. Disengage claws (2 places)
  • Oki ML421 | Maintenance Manual - Page 67
    Oki Data CONFIDENTIAL 3.3.11 Platen Assy (1) Remove the printhead (see 3.3.1). (2) Remove the ribbon protector (see 3.3.2). (3) Remove the pull-up roller Assy (see 3.3.3). (4) Remove the upper cover (see 3.3.1 (1) - (5)). (5) Turn the change lever 1 to the bottom position. (6) Push in the
  • Oki ML421 | Maintenance Manual - Page 68
    Oki Data CONFIDENTIAL 3.3.12 Control Board (NNS) (1) Remove the upper cover (see 3.3.4 (1) - (5)). (2) Remove two screws 1, and release the Control Board 2 and PCB sheet 5 by lifting clamp 4. (3) Disconnect
  • Oki ML421 | Maintenance Manual - Page 69
    Oki Data CONFIDENTIAL 3.3.13 LF Motor (1) Remove the printhead (see 3.3.1). (2) Remove the ribbon protector (see 3.3.2). (3) Remove the pull-up roller Assy (see 3.3.3). (4) Remove the upper cover (see 3.3.4 (1) - (5)). (5) Remove the platen Assy (see 3.3.11). (6) Remove the driver board (see 3.3.12
  • Oki ML421 | Maintenance Manual - Page 70
    Oki Data CONFIDENTIAL 3.3.14 Operation Panel Board (LEOP) (1) Remove the upper cover (see 3.3.4 (1) - (5)). (2) Disconnect the cable 1 from connector 3 of Control Board 2. (3) Disengage claws on both sides from
  • Oki ML421 | Maintenance Manual - Page 71
    Oki Data CONFIDENTIAL 3.3.15 Power Supply Board (TPW) (1) Remove the upper cover (see 3.3.4 (1) the removal steps in the reverse order. Remark on assembly: (1) To mount the Power Supply Board, set the change lever to the top position so that the Switch Lever 7 will not hooked on the microswitches
  • Oki ML421 | Maintenance Manual - Page 72
    Oki Data CONFIDENTIAL 3.3.16 Transformer Assy (1) Remove the upper cover (see 3.3.4 (1) - (5)). (2) Remove AC inlet 1 and AC switch 2 from the frame guide. (3) Disconnect the cable 3 from the connector 4 on the Power Supply Board 5. (4) Remove a screw 6 and disconnect ground cable 7. (5) Remove two
  • Oki ML421 | Maintenance Manual - Page 73
    Oki Data CONFIDENTIAL 3.3.17 Change Lever and Gears (1) Remove the upper cover (see 3.3.4 (1) - (5)). (2) Remove the reset spring 1, then remove the idle gear 2, the tractor gear 4 and the change gear 5. (3) Push back the protrusion of the Change Gear Shaft 6 with a flatblade screw driver to remove
  • Oki ML421 | Maintenance Manual - Page 74
    Oki Data CONFIDENTIAL 3.3.18 Carriage Shaft (1) Remove the printhead (see 3.3.1). (2) Remove the upper cover (see 3.3.4 (1) - (5)). (3) Remove the driver board (see 3.3.12). Remove the FG plate (L) 2. (4) Slide the carriage shaft 1 to the left side (in the direction of the arrow) to remove. (5) To
  • Oki ML421 | Maintenance Manual - Page 75
    Oki Data CONFIDENTIAL 3.3.19 Paper Pan (1) Remove the printhead (see 3.3.1). (2) Remove the ribbon protector (see 3.3.2). (3) Remove the pull-up roller assy (see 3.3.2). (4) Remove the upper cover assy (see 3.3.4 (1) - (5)). (5) Remove the platen assy (see 3.3.11). (6) Release claws A . (7) Lift up
  • Oki ML421 | Maintenance Manual - Page 76
    Oki Data CONFIDENTIAL 3.3.20 Rear Tractor Assy (1) Remove the printhead (see 3.3.1). (2) Remove the ribbon protector (see 3.3.2). (3) Remove the pull-up roller assy (see 3.3.3) (4) Remove the upper cover (see 3.3.4 (1) - (5)). (5) Remove the reset spring (see 3.3.17 (3)) (6) Remove the tractor gear
  • Oki ML421 | Maintenance Manual - Page 77
    Oki Data CONFIDENTIAL 3.3.21 Rear Pressure Assy (1) Remove the upper cover (see 3.3.4 (1) - (5)). (2) right side. Use three remaining pieces on the left side (for ML421). (3) Make sure that the Release Shaft 2 will be on top of the Support spring 4. (4) To assemble the Release Shaft 2, make sure
  • Oki ML421 | Maintenance Manual - Page 78
    Oki Data CONFIDENTIAL 3.3.22 Switch Lever (1) Remove the upper cover (see 3.3.4 (1) - (5)). (2) Remove the change lever and gears (see 3.3.17). (3) Remove the paper pan (see 3.3.19). (4) Remove the
  • Oki ML421 | Maintenance Manual - Page 79
    Oki Data CONFIDENTIAL 4. ADJUSTMENT (1) Be sure to carry out this adjustment with the printer mechanism mounted on the lower cover. (2) Be sure to carry out this adjustment operation on a level and highly rigid work table (flatness: less than 0.039
  • Oki ML421 | Maintenance Manual - Page 80
    Oki Data CONFIDENTIAL No. Item Specification 4-1-1 Gap between the platen and the print head 1) Parallelism justment adVariation Gap between the platen and the print head at the left end and the right end shall be adjusted by rotating the adjust cam. (2) Set the adjust lever at the Range: 1.
  • Oki ML421 | Maintenance Manual - Page 81
    No. Item Specification Oki Data CONFIDENTIAL Drawing Adjust lever A Adjust gear Adjust spring B C Adjustment method Note 1) The head gap shall be measured with the change lever set to rear position. Adjust screw Note 2) The head gap shall be measured positioning the platen gear (R) craw on
  • Oki ML421 | Maintenance Manual - Page 82
    Oki Data CONFIDENTIAL No. Item Specification Gap between the con- 0.3mm or more tact and the monitor Drawing Adjust lever Contact Motor PCB , make sure that the contact touches the motor PCB and it becomes reduced speed mode when the adjust lever is set to range 2 and 4. 42113901 Rev.2 82 /
  • Oki ML421 | Maintenance Manual - Page 83
    Oki Data CONFIDENTIAL No. Item Specification 4-2 Gap between the platen and the paper pan 1±0.5 pan Friction position Rear, Bottom position Adjustment method Confirm followings. (1) When the change lever is set at Friction position, the gap between the platen and the paper pan at the rear side
  • Oki ML421 | Maintenance Manual - Page 84
    4-4-1 Rotation of the push tractor Drawing Change lever (Center friction) Oki Data CONFIDENTIAL Adjustment method To confirm: The tractor gear shall rotate smoothly when the change lever is set at Friction position. Push tractor Slight backlash Tractor gear 4-4-2 Backlash between
  • Oki ML421 | Maintenance Manual - Page 85
    Item 4-5-1 Ribbon feed Specification Drawing Ribbon feeding Oki Data CONFIDENTIAL Adjustment method To confirm: Ribbon shall be fed smoothly when the carriage is moved from side to side. 4-5-2 Running load to spac- 250g or less ing mechanism without a rib- bon cartridge Ribbon To confirm
  • Oki ML421 | Maintenance Manual - Page 86
    Specification 4-6 Engagement of the double gear and the LF motor idle gear of the Platen Assy. LF Motor idle gear Drawing Platen gear(L) Bias gear Oki Data CONFIDENTIAL Adjustment method To confirm: The idle gear of the LF motor and the platen gear (L) and the bias gear of the platen shall be
  • Oki ML421 | Maintenance Manual - Page 87
    Oki Data CONFIDENTIAL 5. CLEANING AND LUBRICATION 5.1 Cleaning [Cautions] 1. Be sure to turn OFF the AC POWER switch before cleaning. Remove the AC power cord from the printer. 2. Avoid dust inside the printer mechanism when cleaning. 3. If a lubricated part has been cleaned, be sure to apply
  • Oki ML421 | Maintenance Manual - Page 88
    Oki Data CONFIDENTIAL 5.2 Lubrication This printer is designed to be maintenance free and requires no lubrication during normal operation. However it is necessary to apply lubricant in case the printer is disassembled, reassembled, cleaned or parts : Remove paper and ribbon dust. Paper path:
  • Oki ML421 | Maintenance Manual - Page 89
    Oki Data CONFIDENTIAL (5) Lubrication point 1. Ribbon feed gear Assy. Planetary gear shaft (upper and lower) EM-30L-A Drive gear shaft (upper and lower) PM-B (0.006-0.002g) 2. Space rack Idle gear shaft (
  • Oki ML421 | Maintenance Manual - Page 90
    3. Platen Assy. Bias gear Oki Data CONFIDENTIAL Grease the contact face of platen gear (L) and bias gear PM-B Platen gear (L) 42113901 Rev.2 90 /
  • Oki ML421 | Maintenance Manual - Page 91
    4. Tractor driving mechanism Change lever Oki Data CONFIDENTIAL Change arm Tractor gear bearing portion EM-30L-A Idle gear teeth EM-30L-A Reset spring Gear bearing portion EM-30L-A Sliding surface of reset
  • Oki ML421 | Maintenance Manual - Page 92
    6. Pressure roller Change arm Oki Data CONFIDENTIAL Support spring Contact portion of support spring and shaft EM-30L-A Contact portion of rear holder and shaft EM-30L-A Sliding portion of release shaft and rear roller holder EM-30L-A
  • Oki ML421 | Maintenance Manual - Page 93
    7. Pull up roller Assy. Pull-up roller frame Pull-up roller shaft All bearing portions of pull-up roller shaft and pull-up roller frame EM-30L-B Oki Data CONFIDENTIAL Gear and post EM-30L-A 42113901 Rev.2 93 /
  • Oki ML421 | Maintenance Manual - Page 94
    8. Main chassis Assy. Grease portion (N: 3 portions) rear side EM-30L-A Oki Data CONFIDENTIAL Grease portion 9. Carriage Assy. Grease portion at rib (N: 9 portions) EM-30L-A 42113901 Rev.2 NK2-10-SUS Bearing portion of guide roller EM-30L-B 94 /
  • Oki ML421 | Maintenance Manual - Page 95
    Oki Data CONFIDENTIAL 6. TROUBLESHOOTING AND REPAIR 6.1 Items to Check Before Repair (1) Check the inspection items specified in the instruction manual. (2) Find out as many details of the trouble as possible from the customer. (3) Inspect in the conditions as close as possible to those at the time
  • Oki ML421 | Maintenance Manual - Page 96
    Oki Data CONFIDENTIAL 6.3 Lamp Display (1) Printer mode display Table 6.2 ALARM CATEGORY ALARM ALARM Paper end alarm ON Paper change ON lever alarm OPERATOR ALARM Paper jam alarm ON Print Head TROUBLE SHOOTING From, cut sheet or bottom paper end Set New paper. Change lever is set
  • Oki ML421 | Maintenance Manual - Page 97
    instruction alarm MPU internal RAM alarm SERIAL ROM alarm INTERFACE ALARM RAM on I/F board alarm I/F not mounted LED DISPLAY 12 15 17 20 PROP HSD UTL NLQ REMARKS Read/write error TROUBLESHOOTING Board. : LED Blink (200ms ON, 200ms OFF) : LED Lights up Oki Data CONFIDENTIAL 97 /
  • Oki ML421 | Maintenance Manual - Page 98
    ALARM 10 12 15 17 20 PROP HSD UTL NLQ REMARKS TROUBLESHOOTING Space IPT is not occurred within in specified timing. Print head does not reach to the home position. • Replace space motor Replace Control Board : LED Blink (200ms ON, 200ms OFF) : LED Lights up Oki Data CONFIDENTIAL 98 /
  • Oki ML421 | Maintenance Manual - Page 99
    Oki Data CONFIDENTIAL Operation Panel Board Control Board Print head Space motor LF motor FAN motor Centro-connector AC connector Switch Transformer Power Supply Board 42113901 Rev.2 99 /
  • Oki ML421 | Maintenance Manual - Page 100
    Oki Data CONFIDENTIAL 6.4 Connection Circuit Check for Printhead and SP/LF Motor (1) Printhead Signal HEAD1 HEAD2 HEAD4 HEAD6 HEAD8 0V HTEMP +50V +50V +50V HEAD9 HEAD7 HEAD5 HEAD3 NC Connector pin number CN1 1 2 3 4 5 6 7 8 9 10 11 12 13 14
  • Oki ML421 | Maintenance Manual - Page 101
    (2) Line Feed Motor Resistance of each coil should be about 10.4Ω. Signal LF1 LF2 LF3 LF4 Connector pin number CN4 1 2 3 4 Oki Data CONFIDENTIAL LF motor (3) Space Motor Resistance of each coil should be about 22.4Ω. Signal SP-U SP-V SP-W SPA SPB SPTEMP 0V CN2 18 17 6 22
  • Oki ML421 | Maintenance Manual - Page 102
    Oki Data CONFIDENTIAL 6.5 Troubleshooting flow chart 1 Power is not supplied. Is the AC cable No Yes End Does DC + 50V out? No Yes Remove Printhead. (Turn power off, then on.) Remedied? No Yes End Replace carriage cable or ribbon feed mechanism. Remedied? No Yes End Replace Control Board. Remove CN3
  • Oki ML421 | Maintenance Manual - Page 103
    Oki Data CONFIDENTIAL No Yes Replace Control Board. Replace Transformer assy. Control Board Remedied? No Yes End CN2 20 1 Replace Power Supply Board. Pin No. 20 19 18 17 16 15 14 13 12 11 10 9 8 7 4 3 1 Signal 50V 0V +5V 0V +12V -8V 42113901 Rev.2 103 /
  • Oki ML421 | Maintenance Manual - Page 104
    Oki Data CONFIDENTIAL 2 No spacing operation (The alarm LED Blinks) Is carriage assembly binding or jammed? No Yes Check around space motor to repair the mechanism of space rack, back up roller, ribbon feed mechanism, and carriage frame etc. Replace Space motor assy. Remedied? No Yes End Replace
  • Oki ML421 | Maintenance Manual - Page 105
    Oki Data CONFIDENTIAL 3 Homing does not end normally Yes No Check around space motor to repair the mechanism. (Space rack, ribbon feed assembly back up roller, carriage frame, support protector and ribbon protector.) Remedied? No Yes End Replace Space motor assy. Replace Space motor assy. Remedied?
  • Oki ML421 | Maintenance Manual - Page 106
    insertion Jam 1 Oki Data CONFIDENTIAL Check the ribbon protector. Check the pull up roller cover is closed properly. Pull up roller cover Ribon Protector Jam 2 (wrinkled paper) Platen Paper Check around pressure roller mechanism. • Front pressure springs are narrow: 3 pcs; wide: 5 pcs) mounted
  • Oki ML421 | Maintenance Manual - Page 107
    Oki Data CONFIDENTIAL 5 Smearing/missing dots Does ALARM LED blink and display alarm? No Yes See Tables 6.2 and 6.3 for troubleshooting information. Replace Printhead. Remedied? No Yes End Replace Control Board. Remedied? No Yes End Replace Carriage cable or Space motor assy. 42113901 Rev.2 107 /
  • Oki ML421 | Maintenance Manual - Page 108
    6 Faint or dark print Is the print head gap set properly? Yes No Adjust the printhead gap (see section 5). Remedied? No Yes End Replace Printhead. Remedied? No Yes End Replace Control Board. Remedied? No Yes End Replace Ribbon feed mechanism. Oki Data CONFIDENTIAL 42113901 Rev.2 108 /
  • Oki ML421 | Maintenance Manual - Page 109
    to left and right. Does the ribbon drive shaft rotate? No Yes Change Ribbon cartridge. Remove Ribbon feed mechanism. Move carriage to left and right. Does the ribbon drive shaft rotate? No Yes Replace Ribbon feed mechanism. Replace Space motor assy. Oki Data CONFIDENTIAL 42113901 Rev.2 109 /
  • Oki ML421 | Maintenance Manual - Page 110
    Oki Data CONFIDENTIAL 8 Line feed trouble Turn the power off, and rotate the platen manually. Does the platen rotate smoothly? Yes No Is the platen gear (L) broken? No Yes Replace Platen assembly. Is the LF motor idle gear broken? No
  • Oki ML421 | Maintenance Manual - Page 111
    Oki Data CONFIDENTIAL 9 Malfunction of switch on operation panel Is the CN1 of Operation panel connected to the CN3 on the Control Board? Yes No Connect the cable properly. Replace Operation panel board. Remedied? No Yes End Replace Control Board. 42113901 Rev.2 111 /
  • Oki ML421 | Maintenance Manual - Page 112
    Oki Data CONFIDENTIAL 0 Data receiving failure Is the SEL LED blinking? No Yes Printer went into the print suppress mode. Wait until printer to receives DC1 code, or change the menu item "Print suppress-Ineffective" when the function is not required. Is the I/F RS232C? No Yes To step
  • Oki ML421 | Maintenance Manual - Page 113
    Oki Data CONFIDENTIAL 10-2 (RS232C I/F) Printer I/F pin assignment. Is the correct cable used? Yes No Change I/F cable. TXD RXD SSD DTR DSR 2 pin, 3 pin, 11 pin, 20 pin, 6 pin. Is ALARM LED blinking? No Yes See tables 6.2 and 6.3 for the troubleshooting. Make sure of the parameters for
  • Oki ML421 | Maintenance Manual - Page 114
    Appendix A PCB LAYOUT PCB list (1) Circuit board TPW (Power Supply Board) (2) Circuit board NNS (Control Board) (3) Circuit board LEOP (Operation Panel Board) (1) Oki Data CONFIDENTIAL CN3 CN1 CN8 CN6 (2) CN1 CN3 CN7 CN5 CN4 CN2 (3) CN10 42113901 Rev.2 114 /
  • Oki ML421 | Maintenance Manual - Page 115
    Oki Data CONFIDENTIAL Appendix B SPARE PARTS LIST Quantity per year: Indicates the recommended number of each part that should be ordered for routine maintenance for one year for 500 units of printers and assuming that the printers are operated for 2 hours/day of 600 hours/year. The following codes
  • Oki ML421 | Maintenance Manual - Page 116
    Oki Data CONFIDENTIAL No. Part No. 1 42040801 42040802 42040901 2 51009409 40165004 51009510 3 42115401 42115402 42115301 Table B-1 Upper Cover Assy Description Upper cover (N) Upper cover (N) Upper cover (W) Sheet guide assy (N) Sheet guide assy (N) Sheet guide assy (W) Access cover assy (N)
  • Oki ML421 | Maintenance Manual - Page 117
    Oki Data CONFIDENTIAL 1 6 8 9 2 10 3 11 7 4 5 42113901 Rev.2 Figure B-2 Printer General Assy 117 /
  • Oki ML421 | Maintenance Manual - Page 118
    Oki Data CONFIDENTIAL No. Part No. 1 51902220 40211004 2 42024002 3 42021802 4 55081107 5 42116101 42116105 6 56609701 7 41923901 8 42124701 42124702 9 42021401 42021501 10 42105001 11 Table B-2 Printer Dell color (black) AC cord for 120V AC cord for 230V 1 1 For ODA 1 1 Printhead (9) 1
  • Oki ML421 | Maintenance Manual - Page 119
    Oki Data CONFIDENTIAL 30 33 9 14 10 29 23 32 35 7 6 34 17 2 15 14 42 22 13 5 4 16 3 11 20 19 37 12 18 B 27 A 8 21 41 1 31 40 A 36 38 39 28 24 26 B 25 42113901 Rev.2 Figure B-3 Printer Unit 119 /
  • Oki ML421 | Maintenance Manual - Page 120
    Oki Data CONFIDENTIAL No. Part Table B-3 Printer Unit (1/2) black) 1 2 For ML421 1 1 3 2 For ML420 5 4 For ML421 3 6 For ML420 5 8 For ML421 3 6 For ML420 5 8 For ML421 1 2 For ML420 1 2 For ML421 1 2 For ML420 1 2 For ML421 1 2 For ML420 1 2 For ML421
  • Oki ML421 | Maintenance Manual - Page 121
    Drive shaft Tractor sheet guide Head cable film (W) Change gear shaft FAN FAN cover FAN cover Shield sheet (Front) Shield sheet (Front) FG spring F Support spring Q'ty Q'ty Required Remarks 1 3 For ML420 1 3 For ML421 1 1 1 1 For ML420 1 1 For ML421 1 1 1 1 For ML420 1 1 For
  • Oki ML421 | Maintenance Manual - Page 122
    Oki Data CONFIDENTIAL 12 10 9 8 6 11 1 14 4 13 3 7 42113901 Rev.2 Figure B-4 Carriage Assy 122 /
  • Oki ML421 | Maintenance Manual - Page 123
    holder assy 1 2 Guide-roller Assy 1 2 Space motor assy 1 Head cable (23) 1 Head cable (23) 15-pin connector 1 Gear case assy 1 Head clamp 1 Head plate 1 Ribbon protector 1 Back up roller holder spring 1 Guide roller spring 1 4 5 ML420 ML421 2 3 1 1 2 1 1 42113901 Rev
  • Oki ML421 | Maintenance Manual - Page 124
    [Pull-Tractor] 2 1 3 Oki Data CONFIDENTIAL [Bottom-Tractor] 4 [I/F Board] 5 6 7 42113901 Rev.2 Figure B-5 Option Spare Parts 124 /
  • Oki ML421 | Maintenance Manual - Page 125
    Oki Data CONFIDENTIAL No. Part No. 1 50098001 2 50097901 3 53077201 53077301 4 51902301 42451601 5 51902302 42451602 6 50098701 50098801 7 55038901 Table B-5 Option Spare Parts Description Pull and bottom tractor assy (L) Pull and bottom tractor assy (R) Tractor cover assy (N) Tractor cover
  • Oki ML421 | Maintenance Manual - Page 126
    controls the following: (a.) Serial interface protocol and data transfer through a serial port. (b.) Message buffer. (c.) Transmission of parallel data to the printer. (2) 75189 An RS-232C standard line receiver (3) 75188 An RS-232C standard line driver. (4) ROM (No Mount) A 64Kbit ROM that contains
  • Oki ML421 | Maintenance Manual - Page 127
    to DB9 ROM 64Kbit Receiver Driver Oki Data CONFIDENTIAL CN1 75188 TD 75189 RD ADR bus ADR/data bus RAM 64Kbit +5 VD printer control board to reset the printer. When the reset is canceled, the 80C51 CPU performs initialization. Initialization consists of setting the 80C51 timer, and setting
  • Oki ML421 | Maintenance Manual - Page 128
    Oki Data CONFIDENTIAL 2.3 Communication Procedure Flowchart 2.3.1 Mode a Ready/Busy Received one character? No Yes Is DSR valid? No Yes DSR High? No Yes Buffer overflow? Yes No Error? No error Store the received character in buffer. Parity error Store 40 H in buffer. Is the printer in
  • Oki ML421 | Maintenance Manual - Page 129
    2.3.2 Mode b Oki Data CONFIDENTIAL X-ON, X-OFF Received one character? No Yes Is DSR valid? No Yes DSR High? No Yes Buffer overflow? Yes No Error? No error Store the received character in buffer. Parity error Store 40 H in buffer. Is the printer in DESELECT state or is the paper low? No
  • Oki ML421 | Maintenance Manual - Page 130
    Oki Data CONFIDENTIAL 3. TROUBLESHOOTING FLOWCHART 3.1 Before Repairing a Fault Before servicing the printer, ask the customer in what situation the trouble occurred and record the response. Before starting troubleshooting, operate the printer in the same situation as that at the time of trouble
  • Oki ML421 | Maintenance Manual - Page 131
    Oki Data CONFIDENTIAL A Yes Are ALE, PSEN, RD, WR, signals as specified in Figure C-6? 180ns 542ns 5V ALE 0V PSEN RD/WR 271ns 5V 0V 542ns 5V
  • Oki ML421 | Maintenance Manual - Page 132
    Oki Data CONFIDENTIAL 2 In receiving by serial interface, printing data is omitted or printing operation is not performed. Are RxD and SSD of Q3 as specified in Figure C-7? No Replace the Q2. Yes Are, WR,
  • Oki ML421 | Maintenance Manual - Page 133
    Oki Data CONFIDENTIAL 3.3 Local Test 3.3.1 Circuit test mode 3.3.1.1 Setting (1) Diagnostic test (set by menu) (2) Test connector Connect the and interface driver/receiver circuit. It then prints characters. To start and stop this test, push the SEL switch on the front of the printer. Details of
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
  • 110
  • 111
  • 112
  • 113
  • 114
  • 115
  • 116
  • 117
  • 118
  • 119
  • 120
  • 121
  • 122
  • 123
  • 124
  • 125
  • 126
  • 127
  • 128
  • 129
  • 130
  • 131
  • 132
  • 133
42113901
Rev.2
1 / 133
Oki
Data
CONFIDENTIAL
ML420/421 PRINTER
Maintenance Manual
ODA