Toshiba CF35E50, Technical Training Manual

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1. OUTLINE
A/V switching circuit performs change-over of video and
audio signals from tuner and external input. The selecting
operation is controlled by microcomputer through IIC bus.
2. IN / OUT TERMINALS
INNER INPUT U/V Tuner (Main)
U/V Tuner (Sub)
.................................. For sub picture (PIP)
EXTERNAL INPUT VIDEO1 With S-terminal
VIDEO2
VIDEO3 (Front)
With S-terminal ........ Excepting CF35E50, CL37E56, CE35E15
VIDEO3 (Back) .................................. Only for CF35E50, CL37E56, CE35E15
OUTPUT VIDEO OUTPUT (V, L, R) .................... Excepting CN27E90
AUDIO ON SUB-PICTURE ................... Only for CN32E90, CN35E90, CN35E95
3. CIRCUIT OPERATION
This circuit consists of A/V SW IC; TA1218N (QV01), and
selects signals from U/V tuner (Main), U/V tuner (Sub),
E1, E2 and E3.
3-1 COMPOSITE VIDEO SIGNAL
The selected video signal is output to pin 38 of QV01, and
separated by comb filter into Y and C. The resulted signal
is input to pins 30 and 32 of QV01, and is output to pins 36
and 34 to be supplied to Q501 (V/C/D).
Video signal for sub picture is output to pin 42 of QV01, and
is supplied to PIP unit (ZY01).
3-2 S-VIDEO SIGNAL
When a cable is connected to S-VIDEO terminal, inner
switch of S-VIDEO terminal is shorted to ground to turn off
the transistor (QV05 for VIDEO1 input) for S-VIDEO
terminal detection. Then chroma input terminal (Pin 14 for
VIDEO1 input) of QV01 turns open. From pins 36 and 34
(Y/C output) of QV01, Y/C signal of selected source is
output.