Table Of Contents - Oki ML490 Maintenance Manual

1. CONFIGURATION ...............................................................................................6
1.1 Standard Printer Configuration ............................................................................................ 6
1.2 Options ................................................................................................................................. 7
2. THEORY OF OPERATION ..................................................................................9
2.1 Electrical Operation .............................................................................................................. 9
2.1.1 Summary ................................................................................................................. 9
2.1.2 Microprocessor and the peripheral circuit ............................................................... 9
2.1.3 Initialization ........................................................................................................... 16
2.1.4 Interface Control ................................................................................................... 17
2.1.5 Print Control .......................................................................................................... 20
2.1.6 SP/LF Motor Control ............................................................................................. 22
2.1.7 Operation Panel .................................................................................................... 25
2.1.8 Alarm Circuit ......................................................................................................... 27
2.1.9 Power Supply Circuit ............................................................................................. 30
2.2 Mechanical Operation ........................................................................................................ 31
2.2.1 Printhead mechanism and operation (See Figure 2-2.) ........................................ 31
2.2.2 Spacing operation (See Figure 2-4.) ..................................................................... 34
2.2.3 Head gap adjusting (See Figure 2-5.) ................................................................... 35
2.2.4 Ribbon drive (See Figure 2-6.) .............................................................................. 37
2.2.5 Paper feed operation ............................................................................................ 39
2.2.6 Paper detection mechanism (See Figure 2-14.) ................................................... 49
2.2.7 Automatic sheet feed ............................................................................................ 51
2.2.8 Paper park function (continuous paper) ................................................................ 53
3. ASSEMBLY/DISASSEMBLY ..............................................................................54
3.1 Precaution for Parts Replacement ..................................................................................... 54
3.2 Service Tools ..................................................................................................................... 55
3.3 Disassembly/Reassembly Procedure ................................................................................ 56
3.3.1 Printhead ............................................................................................................... 58
3.3.2 Ribbon Protector ................................................................................................... 59
3.3.3 Pull-up Roller Assy ................................................................................................ 60
3.3.4 Upper Cover Assy, Access Cover Assy and Sheet Guide Assy ........................... 61
3.3.5 Gear Case Assy .................................................................................................... 62
3.3.6 PC Connector ....................................................................................................... 63
3.3.7 Space Motor, Guide Roller Assy ........................................................................... 64
3.3.8 Space Rack ........................................................................................................... 65
3.3.9 Carriage Cable ...................................................................................................... 66
3.3.10 Backup Roller Holder Assy ................................................................................... 67
3.3.11 Platen Assy ........................................................................................................... 68
3.3.12 Control Board (TFS) .............................................................................................. 69
3.3.13 LF Motor ................................................................................................................ 70
3.3.14 Operation Panel Board (LEOP) ............................................................................ 71
3.3.15 Power Supply Board (TPW) .................................................................................. 72
3.3.16 Transformer Assy .................................................................................................. 73
3.3.17 Change Lever and Gears ...................................................................................... 74
3.3.18 Carriage Shaft ....................................................................................................... 75
3.3.19 Paper Pan ............................................................................................................. 76
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