Epson Stylus COLOR 1520 Service Manual page 68

EPSON Stylus COLOR 1520


Color head nozzle selector circuit
The operating principle for the color head is the same as for the black head except that color print is
performed with data for 3 different colors: yellow, cyan, and magenta. The operating principle for the
color head is as described below:

Nozzle selection circuit
The nozzles for the color head are divided into 3: for yellow, cyan, and magenta with 64 nozzles
for each of them. The nozzle selection signals for each color (YHDATA for yellow, MHDATA for
magenta and CHDATA for magenta) are sent simultaneously in 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.

Common driver circuit
The common voltage (VH) is established to correspond to each of the black printhead
characteristics. This value is stored in advance in the EEPROM when the printer power is off. At
power on, the value is stored in the RAM. The gate array E05B33 (IC6) outputs the serial data
SCDATA of the voltage control signals to the common driver circuit referring to this value. 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 compensate for 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
Head Drive Voltage (VH)
Rev. A