Board - Sony DXC-390 Service Manual

(1) A/D converter circuit for video signal
The analog signal (RGB) that is processed every kind
at the VA-193 board, is converted to 10-bit digital
signal at CXD2310AR (from IC401 to IC403).
Sampling frequency is 14 MHz. The top reference
voltage (approximately 4V) and bottom reference
voltage (approximately 2V) that are the standard
voltage, are set in IC406 (D/A converter), are input via
buffer (IC411). Also, calibration pulse for IC401,
IC402 and IC403 is input after mixing inside between
generated in hard ware (around IC420) and generated
in software via IC406.
(2) CXD9117R and its surrounding circuit
The digital converted RGB signals are input to
CXD9117R (IC404), digital signal processing per-
forms. The IC inside setting is performs by the serial
communication (BUSY, PRN-CS, SDI-3, SDO-3 and
SCLK-3) from a microprocessor. Also, a data commu-
nication with EEROM (IC405) is controlled by
CXD9117R.
(3) CXD9087R and its surrounding circuit
10-bit digital signal after processing in CXD9117R is
input to CXD9087R, performs digital signal process-
ing. The IC inside setting is performed by the serial
communication (CS, SDCK and SDA0-SDA3) from a
microprocessor. The output signal is Y and color
differential signal (Y, CR and CB, every 10-bit). Also,
AHD and AVD that are output at the same time, are
sent to the MB-875 board and ECK is sent to the SG-

265 board.

(4) D/A converter circuit for video signal
Y, CR and CB (every 10-bit) that are output from
CXD9087R, are input to CXD2307R and are convert-
ed to analog signals. The clock frequency for conver-
sion is 28 MHz.
And, an output amplitude can be set independently Y,
CR and CB by setting a reference voltage from IC406.
(5) Clock phase control circuit
14 MHz and 28 MHz clock pulses that is input from
the MB-875 board, are performed phase adjustment
and are output via buffer to each IC (A/D converter for
video circuit, CXD9117R, CXD9087R and D/A
converter for video circuit).
For CXD9117R and CXD9087R, 3.3 V amplitude is
output after converted from 5 V amplitude.
3-2 (E)
3-3. EN-142 Board
The EN-142 board generates the composite signal (VBS
and Y/C) by the encoder IC from Y, CR (R-Y) and CB (B-
Y) that are output from the DP-313 board.
In the another system, RGB signals are also generated by
the discrete circuit.
These output signals are output through the driver circuits.
. . . . . Encode (IC704)
The color differential signals (Y, R-Y and B-Y) are input
to IC704, then encode, VBS and Y/C signals are generat-
ed.
The input Y signal gain is performed at gain control
amplifier in IC704, and also the input R-Y and B-Ysig-
nals gain are performed at GCA in IC703.
Each level setting (Y, SYNC, BURST, SETUP and
White-clip) is performed by IC701.
The title signal from the DP-313 board can be also
mixed to a final output signal of IC704 turning the S701
switch on.
. . . . . RGB generator circuit
RGB signals are made from color differential signals (Y,
R-Y and B-Y) output the DP-313 board. SYNC addition
independently controls ON/OFF for R/B and G.
. . . . . Video signal driver circuit
VBS, Y, C, R, G and B signals output via 75-ohm driver
circuit. HD, VD, C, SYNC and WEN signals also output
via driver circuit.
Also, HD line and VD line using both input and output
are change-controlled by two-way buffer IC712.
DXC-390/390P