Platen Gap (Pg) Adjustment Mechanism; Paper Feeding Mechanism - Epson Stylus Photo 870 Service Manual

EPSON Stylus Photo 870/1270
Table 2-2. Carriage Motor Specifications
Specification
Inductance 30.8 mH +/- 25%
Drive method Constant current chopping
Driver IC LB1947
Unlike a stepper motor, the drive pulses that control the DC motor
cannot control the motor's movement precisely. Therefore, the printer
uses an encoder strip to optically detect the carriage position. The
encoder strip also produces the print timing signal (PTS signal) that the
printer refers to for correct ink ejection timing. For detailed information
on the carriage motor control circuit, see
page 15.
Carriage motor
Timing
Paper Encoder
belt
feed roller strip
Carriage unit
Platen
Figure 2-4. Carriage Mechanism (Top view)

2.3.1 Platen Gap (PG) Adjustment Mechanism

The PG adjustment mechanism, located to the right of the printer
mechanism, consists of the platen gap lever, right/left parallelism
adjustment levers, and the carriage guide shaft, as shown in Figure
2-4. The PG adjustment mechanism is designed to keep the platen
gap adjusted correctly for the paper thickness to prevent ink smears.
The parallelism adjustment levers, mounted on the left and right sides
of the carriage guide shaft, set the shaft parallel to the platen. Moving
the platen gap adjustment lever sets the distance between the platen
and the printhead to one of two positions: 1.2 mm or 1.9 mm.
Description
"C304MAIN Board" on
PG adjust
Parallelis
Carriage
Carriage lock lever
Moving the platen gap lever rotates the mounting pins on the end of
the carriage guide shaft, which are decentralized to make the shaft
move up or down. The user can move the lever to adjust the platen
gap value when loading thick paper.
Table 2-3. Platen Gap Adjust Lever Setting
Paper Lever position
Most media Front (0)
Thick media or ink Rear (+)
smearing problems

2.3.2 Paper Feeding Mechanism

The paper feeding mechanism transports paper loaded in the ASF
using the paper feed rollers and paper eject rollers. A DC motor is
used for the paper feed motor. Table 2-4 lists the paper feed motor
specifications.
Table 2-4. Paper Feed Motor Specifications
Specification
Motor type Brush-type DC motor
Drive voltage +42V +/– 5% (DRV IC voltage)
Coil resistance 29.2 ohm +/– 25%
Drive frequency [Hz] 26.6mH +/– 25%
Control method A3958
Unlike a stepper motor, the drive pulses that control the DC motor
cannot control the motor's movement precisely. Therefore, the printer
uses the encoder wheel and encoder sensor to control the amount of
paper fed. (See "Paper Feed Motor Driver Circuit"
detailed information on the paper feed motor control circuit.)
Chapter 2 Technical Overview
Platen gap adjustment value
0 mm
(1.2 mm between head and platen)
0.7 mm
(1.9 mm between head and platen)
Description
on page 19 for
8