Oki ML421 Maintenance Manual - Page 4

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Oki Data CONFIDENTIAL Contents 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 31 2.2.2 Spacing Operation 34 2.2.3 Head Gap Adjusting 35 2.2.4 Ribbon Drive ...37 2.2.5 Paper Feed Operation 38 2.2.6 Paper Detection Mechanism 48 2.2.7 Automatic Sheet Feed 50 2.2.8 Paper Park Function 52 3. ASSEMBLY/DISASSEMBLY 53 3.1 Precaution for Parts Replacement 53 3.2 Service Tools ...54 3.3 Disassembly/Reassembly Procedure 55 3.3.1 Printhead ...57 3.3.2 Ribbon Protector 58 3.3.3 Pull-up Roller Assy 59 3.3.4 Upper Cover Assy, Access Cover Assy and Sheet Guide Assy 60 3.3.5 Gear Case Assy ...61 3.3.6 PC Connector ...62 3.3.7 Space Motor, Guide Roller Assy 63 3.3.8 Space Rack ...64 3.3.9 Carriage Cable ...65 3.3.10 Backup Roller Holder Assy 66 3.3.11 Platen Assy ...67 3.3.12 Control Board (NNS 68 3.3.13 LF Motor ...69 3.3.14 Operation Panel Board (LEOP 70 3.3.15 Power Supply Board (TPW 71 3.3.16 Transformer Assy 72 3.3.17 Change Lever and Gears 73 3.3.18 Carriage Shaft ...74 3.3.19 Paper Pan ...75 42113901 Rev.2 4 /

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42113901
Rev.2
4 /
Oki
Data
CONFIDENTIAL
Contents
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
...................................................................
31
2.2.2
Spacing Operation
................................................................................................
34
2.2.3
Head Gap Adjusting
..............................................................................................
35
2.2.4
Ribbon Drive
.........................................................................................................
37
2.2.5
Paper Feed Operation
..........................................................................................
38
2.2.6
Paper Detection Mechanism
.................................................................................
48
2.2.7
Automatic Sheet Feed
..........................................................................................
50
2.2.8
Paper Park Function
.............................................................................................
52
3. ASSEMBLY/DISASSEMBLY
..............................................................................
53
3.1
Precaution for Parts Replacement
.....................................................................................
53
3.2
Service Tools
.....................................................................................................................
54
3.3
Disassembly/Reassembly Procedure
................................................................................
55
3.3.1
Printhead
...............................................................................................................
57
3.3.2
Ribbon Protector
...................................................................................................
58
3.3.3
Pull-up Roller Assy
................................................................................................
59
3.3.4
Upper Cover Assy, Access Cover Assy and Sheet Guide Assy
...........................
60
3.3.5
Gear Case Assy
....................................................................................................
61
3.3.6
PC Connector
.......................................................................................................
62
3.3.7
Space Motor, Guide Roller Assy
...........................................................................
63
3.3.8
Space Rack
...........................................................................................................
64
3.3.9
Carriage Cable
......................................................................................................
65
3.3.10
Backup Roller Holder Assy
...................................................................................
66
3.3.11
Platen Assy
...........................................................................................................
67
3.3.12
Control Board (NNS)
.............................................................................................
68
3.3.13
LF Motor
................................................................................................................
69
3.3.14
Operation Panel Board (LEOP)
............................................................................
70
3.3.15
Power Supply Board (TPW)
..................................................................................
71
3.3.16
Transformer Assy
..................................................................................................
72
3.3.17
Change Lever and Gears
......................................................................................
73
3.3.18
Carriage Shaft
.......................................................................................................
74
3.3.19
Paper Pan
.............................................................................................................
75