Epson Stylus Color 1520 Service Manual page 68

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Common driver circuit for the black printhead
Gate array E05B33 (IC6) sends serial data to the head nozzle selection circuit on the head to select
nozzles to activate. The data is transferred to the common driver on the control board to drive piezos
that correspond to each nozzle. The operating principles for the black printhead is as follows:
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Nozzle selection circuit
Nozzles for the black printhead are divided into 2 rows with 64 nozzles each, and 2 deferent types of
nozzle selection signals (BAHDATA and BBHDATA) are sent in serial data to the corresponding rows.
Clock signals (BHCLK) are composed of the pulses from #1 to #64. The nozzles to be activated are
determined by the nozzle selection signals synchronized with the clock signals by the latch signals
(BHLAT). However, the numbers used for the pulses and corresponding nozzles are not the same.
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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 printer power is off. At power on, this value is
stored in the RAM. The gate array E05B33 (IC6) refers to the value for the common voltage when
outputting the serial data (SBDATA) as voltage control signals to the common driver circuit. The
serial data transmission control signals (SCLK, SSTB and SCLR) are used for this operation. The
thermistor controls the common voltage by outputting signals to prevent changes in ink viscosity.
BND0/1,BMD0/1
BA/BHDATA
#1
BHCLK
BHLAT
BHNCHG
COM
BKC,BCHG
Figure 2-25. Black Data Transmission Timing
#64
Printhead Drive Voltage (VH)
Operating Principles
2-25