122
·1
3-5. CAPSTAN
MOTOR
CIRCUIT
'See
Fig. 3-14.
The capstan
motor
rotates in the reproduce
(record/reproduce) and
pause
(record/pause)
modes. Its
torque
is
transmitted
to
the
flywheel
by
a
belt
to
drive the flywheel and capstan shaft.
In
both
the reproduce and
pause
modes,
0514
is
on
to
energize the
head
base
solenoid. When
0514
is
on,
base
cu rrent flows through transis-
tor
0692,
turning
it
on.
Now
the 0 V line
of
the
capstan
motor
servo
amplifier
is
shorted
to
the
ground line
of
the power supply circuit. The
servo
amplifier
is
activated and the
motor
starts
to
rotate. The speed
of
the capstan
motor
may
be
switched between 'standard' (tape speed:
4.76 em/sec)
an.d
'high'
(9.5 em/sec)
by
SPEED
switch S4-2.
PLAY
12
R612
OUT
PAUSE
II
R613
OUT
U601
HEAD
BASE
T
0694
SOLENOID
L692
3-6
TAPE-END
DETECTION
CIRCUIT
See
Fig. 3-15.
The ring magnet, shown in Fig. 3-15,
is
mount-
ed
on the
counter
pulley
shaft and rotates while
the tape
is
running. Variations in the magnetic
field caused
by
the
rotation
of
the ring magnet
turn
reed switch S693 on and
off
. This means
that, when
the
tape
is
moving, the reed switch
turns on and
off
repeatedly.
When the reed switch
turns
on while the tape
is
running, the charge
from
capacitor C609 flows
through the
base
of
transistor
0607
via path @ ,
turning
it
on. When the reed switch turns
off,
0607
turns
off,
as
its
base
current
is
cut
off
.
At
this time, C609 discharges via path @ . Thus,
while the reed switch
is
turning
on and
off
re-
peatedly,
0607
also
turns
on and
off
repeated-
r-------------+39V
,--;:::;;;;;;;:::;:-T----
+
13
V
I
SPEED
+
54-2
-"""'>--.!..jY
SERVO
AMPLIFIER
H
FLASHING
CIRCUIT
CAPSTAN
MOTOR
M692
Fig. 3-14 Capstan
motor
circuit
18
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