Sony HDC-900 Maintenance Manual page 14

1-3. Circuit Description
DU-69/RP-114 boards
The DU-69 and RP-114 boards mount the RPN correction
circuit for the CCD.
VA-196 board
The VA-196 board consists of the video amplifier, gain-up
amplifier, white balancing amplifier, white/black shading
correction circuits, test signal generator, diagnosis circuit
and so on.
The R, G and B video signals input from the CCD block
are passed through the differential amplifier and pre-white-
clip correction circuit. And then the residual component of
clocks is removed at the LPF. The differential amplifier
clamps the black level and also mixes the black shading
correction signal with the video signals.
They are then input to the flair circuit after passing through
the preset gain adjustment control, black set circuit, gain
up amplifier, and white balance amplifier. They are then
PRE KNEE processed in the amplifier in the next stage
and output to the DPR board. The white balancing amplifi-
er performs the white shading correction too.
In addition, the VA-196 board has the test signal generator
which can generate two types of test signals. The test
signals can be used for various adjustments or maintenance
by switching the output signal from the CCD signal to
either of test signals. The adjustment data for the VA-196
board is stored in the EEPROM on the board.
AT-130 board
AT-130 board consists of a microcomputer for system
control and its peripheral circuits. The main program is
written in the EPROM on the board. And the camera
control data is kept in the NVRAM.
Moreover, the AT-130 board is provided with the interface
circuit with the lens and auto-iris control circuit.
1-4 (E)
VDA-55 Board
The R, G, and B signals and Y, P
from the DPR-154 board, and RET (Y/P
from the DAD-37 board are selected by the switch, passed
through the cable compensation circuit (25 m or 50 m),
added with SYNC, and output from the 75 Z driver to the
VCR connector.
After the signal selected from the R, G, B, and Y signals or
RET signal (Y) of the camera is mixed with two types of
zebra signals, character signal, cursor signals, and VF
detail signals, it is passed through the aspect modulation
circuit, added with SYNC, and output to the viewfinder
and TEST OUT connector from the 75 Z driver. When
only the camera is used, the camera and VCR playback
signal are switched by the VCR PB ON signal, and output
from this 75 Z driver. Other VDA-55 boards are also
provided with a self-diagnosis circuit.
DAD-37 board
The DAD-37 board performs digital-to-analog conversions
and transmitting/receiving of the parallel digital signal for
communication in digital form. Parallel-to-serial conver-
sion is performed by the SDI-49 board.
Transmitting system:
. The Y/P /P signals input from DPR-154 board are
B R
formatted for communication in digital and are then sent
to the SDI-49 board.
. The intercom audio and microphone audio signals are
multiplexed by format IC.
. The camera command signal is multiplexed by format
IC.
. The format ID is multiplexed by format IC.
Receiving system:
. Separates the following signals from the parallel-to-
digital signal sent from the SDI-49 board.
Y/P /P video signals (CCU RET)
B R
Intercom audio and program audio signals
Prompter signal
CCU command
Synchronizing signal
. The Y signal is digital-to-analog converted at 74-MHz
rate and the P and P signals are digital-to-analog
B R
converted at 37-MHz rate.
. Send the prompter signal from the HD CCU to the DAP
board.
, and P signals input
B R
/P ) signals input
B R
HDC-900/950 MM