Epson Stylus Photo 925, Service Manual

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EPSON Stylus Photo 925 Revision A
Operating Principles Overview 31
2.1.2.2 Printing Method
For print dot system, Stylus Photo 925 has the following two kinds of printing modes.
T
Multiple shot printing
T
Variable dot printing
The above two printing modes are automatically selected depending on the media and
the resolution setting of the printer driver. The following explains each printing mode.
V
Multiple shot printing
This printing mode is developed to improve the print quality on plain paper or
transparencies in low resolution. The multiple shot printing mode uses normal dot
and the number of dot shots varies from 1 shot to maximum 3 shots depending on
the print data to enable sharp image output even in a low resolution.
V
Variable dot printing
This printing mode is developed to improve the print quality on exclusive paper.
This mode is basically the same as variable dot printing mode used on other
products; micro dot, middle dot, and large dot compose this mode. Print dot size
varies according to print data and this mode enables even sharper image output on
exclusive paper.
2.1.3 Carriage Mechanism
The carriage mechanism consists of Carriage motor (CR motor), Carriage unit (CR
unit), CR guide shaft, platen gap adjustment mechanism, parallelism adjustment
mechanism etc.
2.1.3.1 Carriage Motor (CR Motor)
A DC motor is used as the drive source. Table 2-2 below shows the specifications for
the carriage driving DC motor.
To ensure reliable print quality, this printer employs closed loop control by use of
the DC motor and linear encoder to control the speed and position of the carriage.
At the same time, the control circuit generates the reference signal (PTS signal) to
ensure proper timing for ink discharge. (For the CR motor control circuit, see
2.2.2.2 "Motor Driver Circuit".)
The CR Unit, driven for printing by the CR Motor, moves in the printable area along
the CR Guide Shaft of the printer mechanism.
Table 2-2.CR Motor Specification
Items Specifications
Motor type DC motor with brush
Drive voltage 42 V +/- 5% (voltage applied to the driver)
Armature resistance 27.1
Ω ±
15%
Inductance 19.8 mH
±
25%
Drive method PWM, constant current chopping
Driver IC A3974