Sony WLL-RX55, Руководство по обслуживанию

Страница: 17 / 230

1-9 (E)
WLL-RX55
1-6. Circuit Description
1-6-1. TUN-10 Board
WLL-RX55 is equipped with two TUN-10 boards that
enable to receive two IF signals. Each TUN-10 board is
composed of the tuner block, power supply block, and IF
STREAM output buffer block.
Tuner
The tuner tunes the frequency specified by the CPU from
the 370 MHz IF signal that is input from the external down
converter, and then extracts the OFDM signal. The tuned
IF signal is converted to a 4.5 MHz signal and transferred
to the RX-89 board.
The IF input signal is output from the unit through the
internal buffer.
The serial signal “T DATA” transmitted from the RX-89
board controls the tuner.
Power Supply
The DC-DC converter on this board generates phantom
power
+
10 V for the down converter and
+
5 V for the
tuner and IF STREAM buffer from the UNREG (
+
12 V).
The “OPEN” and “SHORT” signals are detected through
monitoring of the power supplied to the down converter.
Both signals are fed back to the RX-89 board, and then
checked by the host CPU on the AT-156 board. The
SHORT signal is also processed on the RX-89 board, and
then returned to the TUN-10 board as “SHUTDOWN”
signal, which shuts off the power to the down converter.
IF STREAM Output Buffer
This circuit block outputs the IF STREAM signal that is
ASI-converted from the IF TS signal by the RX-89 board
to the external unit. It also converts the LVPECL differen-
tial output of the RX-89 board to the PECL output.
TS: Transport Stream (Stream of MPEG2 bit-rate-reduction data)
ASI: Asynchronous Serial Interface
PECL: Positive Emitter-Coupled Logic
LV PECL: Low Voltage PECL
1-6-2. RX-89 Board
The RX-89 board extracts the TS signal from the IF signal
in the OFDM signal tuned by the TUN-10 board.
The RX-89 board is equipped with two OFDM demodula-
tor circuits corresponding to the TUN-10 boards. The PLD
IC (MERCURY) controls the OFDM reception IC
(CAFE).
MERCURY contains a circuit to switch two interfaces
used in the diversity configuration and two external ASI
inputs (STREAM-1 and 2). The circuit selects the steadiest
signal from the stream received, and sends it to the DEC-
146 board. This switching circuit is called “TS switch”.
OFDM Demodulator Circuit
The OFDM signal transferred from the TUN-10 board is
gain-controlled by the AGC amplifiers (IC108 and IC204),
and transferred to the OFDM reception IC (CAFE), and
then demodulated to the TS signal.
TS Switch
The TS switch contained in MERCURY has two OFDM
inputs and two ASI inputs (STREAM-1 and 2) from the
connector on the rear panel. The switch outputs a signal
selected from these four inputs to the DEC-146 board.
The ASI input is converted to the LVPECL differential
signal through equalizing on the DI-44 board, and then
transferred to MERCURY.