Epson Stylus Color 1520 Service Manual page 69

EPSON Stylus COLOR 1520
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Color printhead nozzle selector circuit
The operating principles for the color printhead and black printhead are the same except that color
printing is performed with data for 3 different colors: yellow, cyan, and magenta. The operating principles
for the color printhead is described below:
T
Nozzle selection circuit
Nozzles for the color printhead are divided into 3 for yellow, cyan, and magenta with 64 nozzles
each. The nozzle selection signals for each color (YHDATA for yellow, MHDATA for magenta and
CHDATA for magenta) are sent simultaneously as serial data. The clock signal (CHCLK) is
composed of the pulses from #1 to #64. The nozzle selection signal and the corresponding clock
signal are synchronized by the latch signal (CHLAT) to determine the nozzle to use. However, the
numbers used for the pulses and corresponding nozzles are not the same.
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Common driver circuit
Common voltage (VH) is established to correspond to each of the black printhead characteristics.
This value is stored in advance in the EEPROM when printer power is off. At power on, the value is
stored in RAM. The gate array E05B33 (IC6) outputs the serial data SCDATA from voltage control
signals to the common driver circuits. The control signals for the serial transmission SCLK, SSTB
and SCLR are used for this operation. The thermistor controls the common voltage by outputting the
signals to prevent changes in ink viscosity.
CKC,CCHG
2-26
YHDATA
CHDATA
MHDATA
#1
CHCLK
CHLAT
CHNCHG
COM
CND0/1,
CMD0/1
Figure 2-26. Color Data Transmission Timing
#64
Printhead Drive Voltage (VH)