Printer Mechanism Operation; Printing Mechanism - Epson LQ-300 Service Manual

2.1 PRINTER MECHANISM OPERATION

This describes the printer mechanism and explains how it works.
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2.1.1 Printing Mechanism

The printing mechanism is composed of the prirdhead, ink ribbon, and ribbon mask. The printhead
is a 24pin head for impact dot printing. Each wire has own drive coil, which causes the wire to
move in and out of the printhead to print each dot. The four steps below describe how these
driving wires work.
A drive signal transmitted from the control arcuit to the printhead drive arcuit is converted to
1.
the proper printhead driving voltage, which energizes a corresponding coil. The energized coil
then causes the iron core to become magnetized.
2. The magnetic force draws the actuating plate toward the core, and the dot wire, which is
connected to the core, rushes toward the platen.
When the dot wire impacts the platen, pressing against the ribbon and paper, it prints a dot.
3.
4. When the driving voltage stops energizing the coil, the magnetic force from the iron core
vanishes. The actuating plate returns to its original position (the position before coil was
energized) with spring action. The dot wire also returns to its original position.
This is the sequence used to print a single dot.
The mechanism is equipped with a built-in thermistor for head temperature detection. The
temperature detected by the thermistor is converted to an electric signal and fed back to the control
circuit.
Wire Resettin
Stopper
Figure 2-1. Printhead Operation Principles
S rin
Dot Wire
Actuating Spring
Operating Principles
2-1