Sony STR-313L - CIRCUIT DESCRIPTION; Program Sensor Circuit; Transistor Circuits (Q202 and 401)

1-2. CIRCUIT DESCRIPTION (See Fig. 1)
Program Sensor
When
the
band
selector
switch
(S1)
and
FUNC-
TION switch (S2) are set to PROGRAM position and
band selector position respectively and the pointer
matches with a station marker, FM or LW station is
automatically selected through optical detection.
(Fig. 2)
1) When the pointer matches only with the .FM
station marker:
a)
The
light
of
IC401
(Photo
Interrupter)
is
inter-
cepted
by
the
marker,
bias
voltage
is
applied
to
the
base
of
Q402
through
R405,
and
Q402
is
turned
on.
b) The collecter voltage of Q402 reduces and D401
is turned on.
c) The terminal @3) of IC201 is grounded through
D201, R204, D401, Q402 and D403.
d) FM circuit operates (The terminal Q3) of IC201
serves as a switch).
Note: When B + voltage is applied to the terminal
Q3) of IC201 through R401, R204 and
D201, the receiver is in AM mode. At the
same time, as Q403 is on, PL401 (FM
indicator lamp) lights.
2) When the pointer matches only with the LW
station marker:
a) As the light of IC401 is not intercepted, Q402
and D401 are turned off. As a result, B + voltage
is applied to the terminal Q3) of IC201 through
R401 and R204. On the other hand, the light
of IC402 is intercepted by the LW station
marker,
b) Q404 and Q405 are turned on.
c) B + voltage is applied to L306 (LW oscillator
coil).
d) LW circuit operates. When Q405 is on, PL402
(LW indicator lamp) simultaneously lights.
(C201
TERMINAL (23)
020!
R204
R40)
L306
(Lw osc)“
STR-313L
3)
When
the
pointer
matches
simultaneously
with
both
the
FM
and
LW
station
markers:
a)
Q402
and
Q403
are
turned
on
by
intercepting
the
light
of
IC401.
On
the
other
hand,
the
light
of
IC402
is
also
intercepted
and
the
bias
voltage
is
applied
to
the
base
of
Q404,
but
because
the
collector
voltage
of
Q403
is
high,
D404
is
turned
off.
The
emitter
voltage
of
Q404
rises
-
and
B
+
voltage
is
not
applied
to
L306
(LW
oscillator
coil)
and
PL402.
Consequently,
only
the
FM
station
signal
is
received.
10401
FM station
marker
The light is
3 ain tercepted
sp: by this portion.
LW station
marker
pointer
'C€402
Fig. 2
Q202 and 401
Q401
operates
to
improve
the
rise
time
of
P1401
(FM
indicator
lamp)
or
PL402
(LW
indicator
lamp)
when
tuning
the
receiver,
and
at
the
same
time
Q401
switches
Q202.
Q202
serves
as
a
high-speed-muting
switch
which
is
turned
on
or
off
as
soon
as
the
station
signal
is
tuned
or
detuned.
(C202
TERMINAL(IS)
Q202
i)
Rac2= ——- R403
(SENSOR BOARD J
Fig. 7
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