Technics ST-9038 User Manual

PART
IT
CIRCUIT
FOR
STAR+SAND
STOP
PULSE
GENERATION
'
¡N
AUTO TUNING,
AND
ADJACENT
CIRCUITS
r
,r
The
clock
pulse
oscillator
circuit consists
of TRSOB
and TRgOg,
with which
a
wave
form
as
shown
on the
previous
page
can
be obtained.
When
the
AT button
is
pushed,
if
appears
at
pin
@
ot
rcul, and
pin
@
becorn.s
"H".
Then, TR90B
turns
ON.
Therefore, the
collector
becomes equal
in
potential
to the emitter and
TR909
turns
ON.
The
collector of
TRg09
is
grounded
and simil,arly
the
base
potential
of TRSOB
decreases. Further,
TR90B
keeps turning
ON and therefore
the emitter
potential
is reduced to a
level Vf
(0.6V)
higher
than
the base
potential,
and then
the collector
potential
drops
as
well.
Accordingly,
TF90B
turns OFF
and the
base
potential
of TR908
rises
to the
original
level.
But the
emitter
turns
off as its
potential
does not immediately
increase
because of the time
constant.
The repetition
of these
operations
results in
oscillation. During
scanning, TRIOb
is
OFF
and the
scanning
speed at that
time is
determined
by Cg'13
and
(R938
+
R156
+
R12gl/lìg37.
When TR105
turns
ON, D114 and D916
are reversely
biased, therefore
R156 and R129 are open
and the
oscillation time constant
is determined
by C913 and R937. Accordingly,
the
oscillating
frequency
is lowered
causing the
scan
speed to
slow
down.
When
TR109 turns
ON at the exact
tuning
point,
the latch of lCg12 is inverted,
and DliB
and
D915
are
biased in forward
direction,
and the oscillation
stops. The
scan speed
in
step scan
is
determinedbythetimeconstantof
Cg13andF937.
ThisisbecauseRlS6andRl2garegrounded
by
S2-2.
2-2-g Extraction
of tuning
signal
TR1 05
TR106
TFt 109
tc102
Stop
signal
D 105
R125
R127
R'l17
VR101
standard
Pin
G)
voltage
Pin
@
voltage
tv1
arrrszz
@
voltage
(DC)
lnput level
IdBl
o
-¿or
o
+¿or
-300K
Af
-4N377
p¡n
@
output
characterist¡c-
0
',I
;
Af
-17-
D1o4
Speed
down s¡gnal
F
fr
TRl 04
VR102
s2-1
off
+300K
-4N377
pin
@
output
charactðrist¡c-

Technics ST-9038 Specifications

General

Brand	Technics
Model	ST-9038
Category	Tuner
Language	English