3-5
CCU-590/P/V1(E)
IV-57B Board
The IV-57B board receives the Y, R-Y, and B-Y signals demodulated on the DM-140 board, converts
them to digital signals using the 27 MHz clock, and then outputs the digital signals to the EN-156B board.
The SKIN GATE signal from the DM-140 board is also converted to digital signal, is delayed in the PLD,
and is then output to the EN-156B board.
Furthermore, this board compares the CHU-SYNC signal from the DM-140 board with the H phase of
TG in the PLD, and then outputs it as H-CONT signal to the TR-133B board.
Y/R-Y/B-Y A/D Converter Circuit
The Y, R-Y, and B-Y signals from the DM-140 board pass through the inverter amplifier, LPF, and
inverter amplifier where their DC components are fed back and clamped. The signals are then A/D
converted to 10 bit, 3.3 V p-p parallel signals by IC117 to IC119 with 27 MHz clock input. The R-Y and
B-Y signals are then output to the EN-156B board through the D-FF. While the Y signal is delayed in the
PLD IC307, and is then output through the D-FF.
SKIN TONE GATE Signal
The SKIN TONE GATE signal from the DM-140 board is input into the D-FF IC107 with 27 MHz clock
input, and is then transferred to the PLD IC307 where the signal is delayed in the same way as the Y
signal. Then the signal is output to the EN-156B board through the D-FF IC121.
H-CONT Signal
Q301, Q303, and IC301 on this board detect the H phase of the CHU-SYNC signal from the DM-140
board, and transfer it to IC303 where the H signal input from the H timing generator in the PLD IC304 is
compared with the H phase of the CHU-SYNC signal. The difference is output to the TR-133B board as
H-CONT signal.
Analog RETURN VIDEO Signal
The analog RETURN signal selected on the DIF-148 board is sent to the IV-57B board where its wave-
form level is adjusted by the video amplifier IC409. Then the signal passes through the MIX amplifier
IC412, and is then output to the modulator circuit on the TR-133B board. In the VF MIX mode where the
main-line signal is mixed with the RETURN VIDEO signal, the RETURN VIDEO level is changed step
by step by IC410. Regarding the main-line signal, the digital signal whose level is set in accordance with
the RETURN VIDEO level by the PLD (RET TG) IC307 is D/A converted by IC408, low-pass filtered,
mixed by IC412, and is then output from this board.
To synchronize the phases of the RETURN VIDEO signal and the main-line signal at the time of Y
mixing, the H/V SYNC signal is extracted from the input analog RETURN VIDEO signal by the sync
separator circuit (Q300, IC309, IC302), and the H/V SYNC signal is transferred to IC307.
SDI RETURN VIDEO Signal
In the SDI RETURN VIDEO input mode, the serial data of the SDI signal selected on the DIF-148 board
is input into IC300 for serial-to-parallel conversion. The converted 10-bit parallel data is input into IC307,
and the output signal is D/A converted by IC408. The analog signal passes through the LPF and the MIX
amplifier IC412, and is then output from this board.
In the SDI RETURN input mode, the Y MIX processing is performed digitally in IC307, which enables
fine setting of MIX ratio.
