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2)
3)
When
motor
speed becomes
slower
(Fig. 8) ;
Time T is determined
by charging-time
of C2
(the inclination of the sawtooth wave). In this
ac servo circuit, the time constant (C2 x R2)
for charging time is determined by R2 for the
specified tape speed.
Circuit operation
when
motor
starts running;
Just after the power
switch is turned ON, Q6
is still turned OFF
since signal is not supplied
from
the
frequency
generator (motor. is not
running).
C2
is charged
rapidly, and greater
voltage than Ek is applied to base of Q7. When
base voltage
of Q901
increases,
ac voltage is
FG
output signal
approx. 900 Hz at
19 cm/s (7 % ips)
collector
of Q2
base
of Q6
collector
of O6
collector
of Q7
base
of Q901
Fig. 6.
| Waveform at each point
qe:
applied
to the
motor
and
the
motor
starts
running
rapidly.
In the FF
mode,
the servo
circuit does not work and ac voltage is applied
to the motor directly.
Then motor rotates at full speed.
FG output signal
(short cycle)
collector
of Q2
base of O6
(short cycle)
|
base of Q7
Ek
LAA
(peak value lower
than Ek}
no pulse
collector of Q7
at base of Q907
(decreases)
Fig. 7.
When motor speed becomes faster
(long cycle)
collector
of Q2
base of Q6
(long cycle)
base of Q7
(peak value
base of Q901
(increases)
Fig. 8.
When motor speed becomes slower
FG output signal
higher than Ek}
collector
of Q7
SEQUENCE
OF SWITCH
OPERATION
Note: The
number
in circle shows
the sequence
of
switch
operation
when
the mode
is changed.
FWD Button Is Pushed
@ S615 turns ON.
@ S608 turns ON.
In the
REV
play mode,
the tape
Brake
solenoid
(PM602)
is energized.
direction relay (RY601) and solenoid
(PM603)
are
energized
(FWD
play
mode)
@® $602 turns ON.
® S610 turns ON.
Pinch roller solenoid (PM601) is
energized,
Reel motors start to rotate.
@® $605 is changed to FF, PLAY
@ S614 turns ON.
position.
The
voltage
across
B+ voltage for bias osc circuit
brake
solenoid
(PM602)
de-
is not
supplied
yet because
creases.
S613
turns OFF.
© S618 turns ON.
If the POWER
MAIN switch is
set to AUTO
OFF, the machine
turns
off automatically
at the
end of the tape.
©
S620is changed to PLAY position.
® S613 ischanged to PLAY position.
Dummy resistor R611 in B+ circuit
B+ voltage is supplied to bias osc
is cut off by S620.
circuit.
©
S604 is changed to PLAY position.
@
S612 is changed to PLAY position.
The
voltage
across
pinch
roller
solenoid (PM601) decreases.
(After
one
second
since
S604
is
changed
to
PLAY
position
(6)).
FF Button Is Pushed
® S611
is changed
to FF
position.
@
$607 turns ON.
FF
relay
(RY602)
is energized
(FF position).
The
motor
circuit
is changed
to
supply the rated voltage to each reel
motor.
@® Self-locking
contact (1) of FF relay
@ Contact
(2)
of
RY602
is closed.
@ Contacts (3) and (4) of RY602
are
RY602)
i
:
(
02) is closed
Brake solenoid (PM602) is energized.
closed.
Pinch
roller
solenoid
(PM601)
is
de-energized.
AC rated voltage is supplied to reel
motors.
@® S602 turns ON.
@
$610 turns ON.
Reel
motors
start
to rotate.
These actions @ are not
@® S605
is changed
to FF
position.
@® S614 turns ON.
related to FF operation.
The
voltage
across
brake
solenoid
(PM602)
decreases.
—12—
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