Sony KP 48S70, Training Manual

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21
Switching and Comb Filter (S Models)
Overview
This section discusses the inputs to the S model RA-3 chassis. The S
models have two inputs for composite/S Video and one shared input that
accepts composite, S video and component video. These signals are
switched and if composite video is input, it is sent to the comb filter. The
comb filter separates the Y and C signals and sends them to the A/V
switch. The A/V switch switches the comb Y or component Y signals to
the main Y path. The component U and V signals are switched by IC1903.
Video Inputs
The Video 1 and 2 inputs accept composite and S video inputs. If an S
video cable is plugged in, then the composite video input is disabled. This
is because when the switch in the S video connector is closed, a line on
IC1101 A/V Switch is grounded. The Video 3 input also contains a com-
ponent input. If Video 3 is selected and there is a cable plugged into
J1106 Pr, then the Video 3 composite and S video inputs are disabled.
This is because the switch in J1106 activates the Video 4 input. This will
switch the Y from the component input to the main Y path. IC1903 YUV
Switch switches the color components.
Switching and Comb Filter
The composite video inputs are input to IC1101 A/V Switch. Whichever
input is chosen is output at IC1101/41. This signal is sent to Q1103 and
Q1104 Buffer and then the filter network consisting of Q1701, FL1701,
Q1702 and Q1703. After filtering, the signal is input to IC1702 Comb
Filter. There is also a 3.58 MHz signal input to IC1702/11 CK In from
IC206 YCJ. The comb filter separates the Y and C signals in the compos-
ite video signal. The C signal is output from IC1702/23 C Out to a filter
network consisting of Q1704, FL1702, Q1707 and Q1708. This signal is
then sent to IC1101/43. The Y signal is output from IC1702/25 Y Out to a
filter network consisting of Q1705, FL1703, Q1706 and Q1709. This sig-
nal is then sent to IC1101/45. These signals are switched through IC1101
A/V Switch and become Main Y and Main C.
If the switch from the S video input is closed, the internal switch in IC1101
changes position and switches the Y and C from the S video input to the
outputs at IC1101/37 and 39. If the component video input is selected,
the component Y is switched from the Y4 input to IC1101/39.
IC1101 is also capable of switching any one of the input to the Sub Y and
C Out pins 56 and 58.
3 4
1 2
IC1101
A/V SWITCH
CXA 1845
19
17
21
15
16
18
24
28
J1101
VIDEO 3 IN
S VIDEO
VIDEO
L (MONO)
R
AUDIO
Y
PB
PR
J1106
C3
Y3
SSW-3
V3
L3
R3
Y4
SSW-4
TO IC1903
YUV SWITCH
KP53S70 VIDEO 3 INPUT
34
35
A BOARD
SDA
SCL