Olympus OEP-3, Service Manual

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4-38
OEP-3 V1 (UC)
Head voltage correction
The head voltage can be increased or decreased by changing a VCONT signal. In the correction below, a
VCONT signal is digitally controlled (using software) by using the D/A port output of CPU (IC11).
.
Correction by feed pitch
When data is printed at the same head voltage, the print density becomes thicker as the feed pitch
becomes narrower. Therefore, an offset is made in each feed of ordinary horizontal print (FULL, four-
division, and 16-division) and vertical print (two-division and eight-division).
.
Correction by thermal head temperature
When data is printed at the same head voltage, a difference occurs in the print density as the head
temperature becomes higher or lower. Therefore, the head voltage is adjusted by the head temperature
just before printing.
PLD for color balance adjustment
A
γ
table is switched in the timing in which the horizontal and vertical directions of print data were set
when adjusting the color balance. By this, the divided print whose color tone was changed is carried out.
2. Input/output timing
nPRINTING and nHEAD_ACTIVE_IN signals are an enable signal of a thermal head. When these
signals are both “L”, the thermal head enters the print enable state.
An nHEAD_ACTIVE_IN (
_
P) signal is also used as an enable signal of IC223 and IC226. When this
signal is “L”, IC223 and IC226 are in the print enable state. In this state, the rising edge of a
PRINT_PULSE_IN signal accepts a PQC DMA transfer.
When the next PRINT_PULSE_IN signal is input, it is transferred to the thermal head together with a
shift clock (HEA/D_CLK), data latch output signal (HEAD_LATCH), and strobe output signal
(HEAD_STRB) as eight-port serial data. The DMA transfer of data in the second line is also accepted in
parallel.
The data in the first line that was input as described above is transferred to the head drive circuit in
synchronization with the fourth PRINT_PULSE_IN signal. The data is also output to the thermal head in
synchronization with the fifth PRINT_PULSE_IN signal. Therefore, a PRINT_PULSE_IN signal is more
input to PQC IC than the number of actual print lines by four.