Operation Principles - Epson LQ-870 Service Manual

OPERATION PRINCIPLES

PRINTER MECHANISM OPERATION ............................................ 2-1
2.1
Printhead Mechanism ........................................................... 2-1
2.1.1
2.1.2 Carriage Movement Mechanism ....................................... 2-2
Paper Advance Mechanism ................................................. 2-3
2.1.3
2.1.3.1 Paper Feeding Mechanisms ..................................... 2-4
2.1.3.2 Paper Insertion Entrances ......................................... 2-6
Ribbon Advance Mechanism .............................................. 2-11
2.1.4
2.2 POWER SUPPLY OPERATION ........................................................ 2-12
Power Supply Overview ....................................................... 2-12
2.2.1
Supply Circuit Operation ...................................................... 2-12
2.2.2
2.3 CONTROL CIRCUIT OPERATION ................................................... 2-14
Control Circuit Operation Overview ................................ 2-14
2.3.1
Reset Circuit ............................................................................. 2-17
2.3.2
Sensor Circuits ........................................................................ 2-18
2.3.3
Carriage Motor Drive Circuit .............................................. 2-19
2.3.4
Paper Advance Motor Drive Circuit ................................. 2-20
2.3.5
Printhead Drive Circuit ......................................................... 2-21
2.3.6
Parallel Interface Circuit ...................................................... 2-22
2.3.7
EEPROM Control Circuit ...................................................... 2-22
2.3.8
LIST OF FIGURES
Figure 2-1. How the Printhead Works .............................................. 2-1
Figure 2-2. Carriage Movement ........................................................... 2-2
Moving the Paper-Thickness Adjustment Lever ..... 2-2
Figure 2-3.
Figure 2-4. Friction Feeding Using the Top Entrance .................. 2-3
Push Tractor Operation ................................................... 2-4
Figure 2-5.
Pull Tractor Operation ...................................................... 2-5
Figure 2-6.
Push-Pull Tractor Operation ........................................... 2-5
Figure 2-7.
Moving the Release Lever ............................................... 2-6
Figure 2-8.
Friction Feeding Using the Top Entrance .................. 2-6
Figure 2-9.
Push Tractor Feeding Using the Rear Entrance ...... 2-7
Figure 2-10.
Figure 2-11. Pull Tractor Feeding Using the Rear Entrance ........ 2-7
Figure 2-11-1. Push-Pull Tractor Feeding Using the Rear Entrance . . 2-7
Figure 2-12. Pull Tractor Feeding Using the Bottom Entrance . . . 2-8
CHAPTER 2
2-i
REV.-A