Epson FX-870 Service Manual

Principles of Operation
6
This chapter explains the mechanical and electrical operations of the FX-870/1170. At the end of
the chapter, there are tables for component-level diagnosis of the main logic board and the power
supply board.
Printer Mechanism Operation
This section describes the FX-870/1170 printer mechanism and explains how the printer works.
The FX-870/1170 printer mechanism features a 9-pin impact dot printhead for serial printing. It
has four main parts:
l the printhead mechanism
l the carriage movement mechanism
l the paper feed mechanism
l the ribbon advance mechanism
Each of these is described below.
Printhead Mechanism
The printhead mechanism consists of the printhead itself, the ink ribbon, and the platen. The
printhead contains a column of 9 wires. Each of these wires has a drive coil, which causes the wire
to move in and out of the printhead to print each dot. The three steps below describe how these
driving wires work.
1. The control circuit outputs drive signals to the printhead drive circuit. This changes the
printhead drive voltage, and current flows through the corresponding printhead coil. The coil
acts as a solenoid and generates a magnetic force.
2. This induced force causes the plate to approach the coil rod, and the associated dot wire is rapidly
ejected to impact on the platen.
3. The dot wire presses the ink ribbon up against the paper as it hits the platen, and in this way,
prints a dot on the paper.
Epson FX-870/1170
6-1

Epson FX-870 Specifications

General

Brand	Epson
Model	FX-870
Category	Printer
Language	English