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2. SCREEN
INDICATION
CIRCUIT
The screen
indication circuit is composed of 1C101,
waveform, whose pulse width changes according to the
Q101~ 0103
as shown
in Fig. 3. The principle of the
tuning voltage during the horizontal period, is produced.
screen indication circuit is as follows.
This pulse is passed through the differential
circuit to
The
saw-tooth
wave,
which
synchronizes
to the hori-
make
a pulse with a specified width at the rise section
zontal pulse, is superimposed on the DC current divided
of the pulse, and bar indication is done by raising the
from the tuning voltage, and by comparing this with the
base bias of the video-out transistor of the color (VHF
input threshold voltage of the IC and amplifying it, the
L: GREEN, VHF H: RED, UHF: BLUE) corresponding
to the reception band when this pulse is present.
Ou
LI02
OHO
Lol
aes
DIZ | DUE
R137
Horiz. pulse
QIO3
UP- signal
DIOS
RIIO
(1c1i0o3 @)
ie
DOWN- signal
(icio3
())
D104
RII
cll
Presence/absence
of sync. signal
1C104 @)
( Present a)
Absent "H
INO. SWITCH
HL4v
Fig. 3
= 13=
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