Sony HDC-900 Maintenance Manual page 15

SDI-49 board
The SDI-49 board converts the parallel Y/P
multiplexed by the DAD-37 board to a serial digital signal
and outputs it from the SERIAL OUT connector. And
SDI-49 board also converts the serial digital signal to an
optical signal and outputs it to the HD CCU.
The serial digital signal input from the RX-28 board is
separated from clocks and is converted to a parallel digital
signal. The converted signal is then output to the DAD-37
board.
RX-28 board
The optical signal transmitted from the HD CCU is
converted to an electric signal by the RX-28 board and is
output to the SDI-49 board. And the photo-reception level
is detected by the RX-28 board and the detection value is
output to the SDI-49 board.
AU-271 board, DU-104 board
The AU-271 board consists of the following circuits:
. Two intercom input amplifiers
. Two microphone input amplifiers
. Power supply for the above input amplifiers
. Two intercom receiving output amplifiers
. Two PGM output circuits
. TRACKER input/output circuit
. VTR intercom circuit
. Earphone output circuit
The input signal at the INCOM connector is converted to
_20 dBu in level and is output to the DAP-24 board, after
the microphone selection (carbon or dynamic microphone)
is made and the microphone level +6 dB, 0 dB or _6 dB is
selected.
The input signal at the MIC connector is also converted to
_20 dBu in level and is output to the DAP-24 board, after
the microphone level _20 dB, _30 dB, _40 dB, _50 dB,
or _60 dB is selected. The same signal is output to the
VTR connector in parallel. The microphone connected to
the MIC connector is selectable from the microphone
without power, AB powering or phantom microphone.
The intercom receiving signal is adjusted in level by EVR,
with which the PGM and TRACKER signals are mixed,
and is then output through the buffer. By setting the
internal switch of DU-104 board, the intercom receiving
signal can be interfaced with the optional RTS kit.
The PGM signal is adjusted in level by EVR, with which
the intercom signal is mixed, and is then output through the
output amplifier.
HDC-900/950 MM
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DAP-24 board
/P signal The intercom signals and microphone signals in two
B R
channels each, which are sent from the AU-271 board, are
analog-to-digital converted by the DAP-24 board and are
output via the DAD-37 board to the HD CCU.
The digital audio signals sent from the DAD-37 board is
converted to analog intercom signals and analog program
signals in two channels each and are output to the AU-271
board.
The DAP-24 board is equipped with the PLL circuit to
synchronize the video signal with clocks as reference
during analog-to-digital or digital-to-analog conversion.
In addition, the DAP-24 board has the detection circuit to
detect the connection status with the HD CCU, standby
intercom circuit, interface circuit with the viewfinder and
diagnosis circuit.
The prompter signal from the DAD-37 board is output
from the PROMPTER OUT after being decoded and
digital-to-analog converted.
SG-268 board
The SG-268 board consists of the pulse generators.
. Generates various pulses as the reference of the VCO
(74.25 MHz or 74.175 MHz) on the circuit boards. This
pulse generator synchronizes the HD CCU or external
sync signal input.
. Generates various marker signals.
. Outputs the status signal or diagnosis data as a character
data from the character generator.
. Stores the oscillation frequency, its adjustment data in
the EEPROM on the SG-268 board.
1-3. Circuit Description
1-5 (E)