Epson LX-300, Service Manual

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Operating Principles
LX-300 Service Manual
2.1.5 Ribbon Shift Mechanism
This printer can be equipped with a color upgrade kit to print in color. The printer performs
printing unidirectionally. The option is composed of the shift mechanism. The
ribbon feed mechanism is shared in common black and the shift
mechanism shifts the ribbon cartridge up and down.
Table 2-2 shows the CS motor assembly specifications. The motor control system is open-loop, so
that when the color is being changed, the positioning is controlled by stepping pulse.
Table 2-4. CS Motor Assembly Specifications
Category
Requirement
Type
4-phase, 48-pole, PM-type stepping motor
Drive Voltage
35 VDC 10Yo
Coil Resistance
150 ohms (per phase, at 25° C or 77°
Drive Pulse Frequency
Color shift 500 pps
Excitation Method
Constant-vottage 2-2 phase excitation
The ribbon shift mechanism consists of the color ribbon and color upgrade kit. The color upgrade
kit is composed of the motor assembly, shift gear/cam, motor driver and color ribbon
sensor. The l-inch-wide color is separated into four equal-width bands of different colors.
The ribbon shift mechanism shifts the ribbon cartridge up and down.
When the color ribbon cartridge is loaded, it is possible to print in up to seven colors. One of the
four colors on the ribbon is selected by the color ribbon cartridge motion, which inserts a portion of
the plastic posts into the slots in the printer mechanism as a fulcrum. Figure 2-9 illustrates the color
shift mechanism. The mechanism shifts the ribbon cartridge by converting the gear rotation to
liner motion (up and down) of the color ribbon cartridge, using color shift cam gear.
Any color band can be selected rotation of the motor assembly, using the color home
position (the position of the black color band) as a starting point and reference position. Home
position is recognized by the
motor assembly stepping pulse. When printer is power on, the
motor assembly is at any phase position at first. Next, the motor assembly is turned for
235 steps ( black yellow). Then, the motor returns one step black), and the ‘motor is
stopped. Finally, the motor returns 223 steps black) and stops. This position is home
position.
Table 2-5 gives coloring sequences. For halftones, as shown in the table, a color is created by
printing one color on top of another.
Table 2-5. Coloring Sequences
Print Ribbon
Print Color
First Printing Printing
Black Black
—
Magenta Magenta
—
Cyan
cyan
—
Yellow Yellow
—
Green
Yellow
cyan
Orange Yellow Magenta
Violet
Magenta Cyan
Note: The printer prints the brighter color first to prevent the ribbon from stained
2-8