V1 Board - Sony FWD-32LX1R Service Manual

A microcomputer accepts the SIRCS signal received in the photosensing block on the H3 board or the
SIRCS signal received in a Control-S input block (J1001). When a jack is not inserted in J1001, the
SIRCS1 signal that the H3 board received is passed through a buffer (IC1207) via Q1005 as an SIRCS2
signal and input to pin 48 of a microcomputer. When a jack is inserted in J1001, the contact of J1001 is
separated from an SIRCS1 signal and the signal from the jack is input to the microcomputer as an
SIRCS2 signal. The SIRCS2 signal is sent to the microcomputer (29-pin) as an SIRCS_IRQ signal using
a buffer (IC1207), detecting the rising edge for interruption.
A current is supplied from CN1203 through a constant-current circuit (IC1202) and integration circuit
(consisting of Q1209, Q1211, Q1214, and Q1215) to drive the LED of Sony logo on the H2 board. A
pulse signal (LED_IND) signal is input from a microcomputer to the constant-current circuit to change
the pulse width and control the brightness.
The KEY1 and KEY2 signals from the H1 board are an analog voltage signal. The voltage varies
depending on the pressed key and is input to the analog port of a microcomputer for processing. Other
voltages and signals input to the analog port are D3.3 V, 5 V, Q_SENSE1, and Q_SENSE2. D3.3 V and
5 V are used during self-diagnosis. Q_SENSE1 and Q_SENSE2 are used to detect the connected option
board.

3-3. V1 Board

The composite signal, Y/C signal, and component signal from an option board and the component signal
from an INPUT2 terminal are input to a video switch (IC3003) once. The component signal discriminates
a signal by reading H and V signal frequencies using the register of IC3003. The RGB signal from an
option board is selected using an RGB switch (IC3001) and then output from CN3900 to the D3 board.
The signal input to the video switch is output to a SECAM decoder (IC3300) and NTSC/PAL decoder
(IC3505).
The SECAM decoder (IC3300) separates a SECAM signal from Y to C and converts it from analog to
digital. The NTSC/PAL decoder (IC3505) separates signals other than a SECAM signal from Y to C and
converts them from analog to digital. An eight-bit Y/C signal is output, and AD calibration is performed
by the gain adjustment of Y and C signals. The output value at that time is read using a processor
(IC2004) on the D3 board and automatically adjusted by software so that it is a target value. Also, an H/
V sync signal and dot clock are generated using a decoder.
A microcomputer full-automatically discriminates color using the color discrimination function of a
decoder. It also extracts caption information from the video signal, using IC4300, that is output from a
video switch (IC3003), superimposing it for display as an RGB signal (M_CCDOUT) using an NTSC/
PAL decoder.
The output signals of each decoder (IC3300 and IC3505) are input to a selector (IC3701). The output
signal of a SECAM decoder is input to channel B, and the output signal of an NTSC/PAL decoder is
input to channel C. The digital RGB (YUV) signal from CN3002 is directly input to channel A of a
selector.
For an interlace signal of 15 kHz, the output signal of a selector (IC3701) is input to DRC (IC4101) and
IP-converted into a progressive signal of 31.5 kHz for double-density processing. The processed signal is
input to channel B of a selector (IC3901) in the later stage. Signals other than described above are
directly input to channel C of IC3901. The signal input to IC3901 is input through CN3900 to the scaler
on the D3 board.
An audio signal is input from the D3 board and option board to an audio switch (IC3006). The selected
signal is input through CN3900 to the D3 board and then input to the K1 board.
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FWD-32LX1R