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7.3,
CONTROL
CIRCUIT
See Fig. 7-3 for an outline of the control cir-
cuit.
Play Mode
1. When
the PLAY
switch
S7 is turned
on, pin
12 of IC301
is switched
to H level, resulting
in +B
being
applied
to Q315
via R346
and
D319, thereby turning the transistor on.
.
2.The
pinch
solenoid
SL1
is thus activated
to
commence play mode.
Recording Mode
1. Load a cassette half with the erasure prevention
tabs
still
intact
(in which
case
the
erasure
prevention switch $138 will be in the
NO HOLE
position). When the PLAY switch S7 switch and
REC switch S12 are turned on together, pins 12
and 10 of IC301 are switched to H level.
2. Due to the H level on pin 10, a current flows
via
D330,
R356,
Q3820
and
Q3819,
thereby
turning
these
two
transistors
on.
The
REC
solenoid SL4 is thus activated, and the REC/PB
selector switch set to the REC position.
3. And
as has already been described under ''Os-
cillator
circuit",
the bias
oscillator
circuit
is
also activated when pin 10 of this IC is switched
to H level.
4. As a result of pin 12 being switched to H level,
pinch solenoid SL1 is activated as was described
above under ''Play Mode'"'.
5.If the erasure
prevention
tabs of the loaded
cassette
have been
broken
off (and S13 thus
switched
to
the
HOLE
position),
pin
9 of
IC3801
will
be
shorted
to
ground,
thereby
preventing
pin
10
from
being
switched
to
H level.
_ Recording
mode
will therefore
not
be possible.
Fast Forward (Rewind) Mode
1.When
the FF
switch
S9 is turned on, pin 15
of IC801
is switched
to H level, resulting in
+B being applied to Q317 via R851 and D324
to subsequently turn the transistor on.
2. The FF solenoid SL2 is then activated to start
fast forward mode.
3.The
operation
is basically
the
same
during
rewind
mode.
Pin
138 of IC301
is switched
to H level when the REW switch S10 is turned
on,
resulting
in
the
activation
of the
REW
solenoid SL3.
Pause Mode
1.1f the PAUSE
switch $11 is turned on during
playback
or recording mode, pin 12 of IC801
is switched
from
H
to L level, resulting
in
@Q315 being turned off.
CT-F615
2. Pinch solenoid SL1 will thus be released, there-
by temporarily stopping tape transport.
Timer Start
@ Play Mode
1. The timer switch S16 is in the PLAY
position
when the power switch is turned on by timer.
2. At the same time that the power supply voltage
rises, Q325 is turned on by the C844 charging
current.
8. And since pin 12 of IC3801 is at H level, current
will be applied to the base of Q315.
However,
because
of the time constant circuit consisting
of R348, C334 and R347, Q316 will be turned
on
for 2 to 3 seconds,
consequently
keeping
Q315 turned off during this period.
4. Once C334 is fully charged up, Q316 is turned
off and Q815 turned on.
Pinch solenoid SL1
is then activated to start playback mode.
®
Recording Mode
1. The timer switch
S16
is in the REC position
when the power switch is turned on by timer.
2.Pin
12 and 10 of IC301 are both switched to
H level at the initial onset of power.
The REC
solenoid
is thereby activated
(since pin 10 is
at H level) and the bias oscillator started.
38. And
as was
described
above
for '"'Timer Play
Mode'',
the
pinch
solenoid
SL1
is activated
some
2 to 3 seconds
after the power
switch
is turned on.
Timing for Direct Switching Operations
To enable the CT-F615
to be switched direct-
ly from fast forward or rewind mode to playback
mode
without
generating
tape
slack
or
other
mechanical
trouble,
tape
transport
has
been
designed to stop for fixed period of times during
such switching operations.
Direct
Switching
from
Fast
Forward
(Rewind)
Mode to Playback Mode
1.Since
pin 14
of IC801
is at H level during
fast
forward
(or
rewind)
mode,
a charging
current
is applied to C355 via D822.
At the
same
time, a current
is also applied
to Q316
via D822
and R349, thereby maintaining Q316
on.
2. When the PLAY
switch
S7 is turned
on, pin
12 of IC301 is switched to H level, and pin 14
to -L level.
The C835 discharge current, how-
ever,
is applied to Q316
via R349
for about
0.3 seconds
longer, thereby
keeping this tran-
sistor turned on for that extra time. Activation
of pinch solenoid
SL1 is thus delayed by that
same period of time.
15
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