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This circuit is designed to switch the chroma signal from TV or AV source and will be applied
to pin 16 of IC280, SECAM colour demodulator
IC. The composite video signal from the TV is
inputted to pin 5 of IC290, and from the AV terminal is inputted to pin 3 of IC290. Selected
composite video signal from TV or AV is outputted from pin 4 and is inputted to pin 1.
When the system is selected to SECAM, the composite video signal is outputted from pin 15
and inputted
to pin 16 of IC280 as SECAM chroma signal, through
the band pass circuit
consisting
of C285,
R282,
L281
and C288.
C286
compensates
for the band
pass
characteristics
of the AV mode.
The signals
which drive the internal
switches
in IC290 are supplied
from pin 9 (TV/AV
switching) and pin 41 (SECAM or others switching) of the CPU, and are inputted to pins 9/11
and 10 through the inverter circuits, Q716 and Q292.
CPU
IC290
Q716
Iclol
TVIAV 9
................ .. . ........
Video/Chroma
Q291
SECAM 41
....................
7
0
'3
AV
c287
R283
1
14
3
...........
.Z
-lb
+1
C286
~288
15
I
16
Q891
-m
S
stem
Pinl O
Auto
H
SECAM
H
Other
L
m
R282
4
i
I
i
i
~
~EAcM
\ CHROMA IN
.—.
— ---
L281
T
J
C285
V
R894
Input
IC280
SECAM
Demodulator
16 Chroma Input
1
I
SECAM
8and pass
.-
-27-
A7-A
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