Akai GXC-750D

1. ТАРЕ SLACK ELIMINATION CIRCUIT
1) This deck employs a double capstan drive system.
2. PARKING BRAKE CIRCUIT
1) To prevent tape slack from forming at Stop mode,
Consequently, when a play mode is effected with a
great deal of slack, tape may triangle into the
mechanism to cause trouble. Or even when there is
only a slight slack, it takes a long period of time to
otbain the optimum loop tension and correct bad
head-to-tape contact.
The purpose of this circuit is to take-up the tape
slack beforehand to obtain correct tape tension for
smooth operation and to prevent the undesirable
conditions.
2) When the cassette is not loaded, the cassette pack
detection circuit micro switch SW902 is OPEN.
Therefore, base electric current flows as R96 >
D60 ^ R98 ^ TR23 and TR23 is ON.
Also, when the Eject is effected, SW902 closes.
But in this case, Eject Switch SW903 is OPEN to
cause base electric current to flow R97 一 D61 >
D98 > TR23 and maintain TR23 ON condition.
When the cassette is loaded, Eject Switch SW903
closes, and since SW902 is also closed, electric
current is not supplied to TR23 base and TR23 is
OFF. When TR23 is turned OFF, C33 charging
current flows as R101 > C33 > R103 > D16 >
TRS. Also, because the Take-up Reel Motor and
the interlocked rotary magnet are not rotating at
this
time,
IC4
output
terminal
(8)
is
at
a
high
level.
While
C33
is
being
charged,
TRS
base
electric
potential increases to turn TR5 ON. When TRS is
turned ON, electric current flows to the Supply
Reel Motor through D78, R26 and rotates it to
remove the tape slack.
3) After C33 is completely charged by the electric
current
R101
>
C33
>
R103
>
D16
>
TRS,
TRS
is turned
OFF.
Or
else,
even
when
C33
is still
being
charged,
Take-up
Reel
Motor
may
start
to
rotate
when
Supply
Reel
Motor
rotates
and
completes
to
Pull-up
tape
slack.
When
Take-up
Reel
Motor
rotates,
interlocked
SW901
rotary
magnet
begins
to
rotate.
The
resulting
pulse
electric
current
flows
a C35
> TR25
> C36
>
D66
> ВІЗІ
> C38
and
charges
C38
to increase
TR27
base
electric
potential
and
turn
TR27
ON.
When
TR27
is turned
ON,
IC4
input
terminal
@
becomes
ground
electric
potential
through
D69
and
TR27
and
therefore,
output
terminal
becomes
low
level
by
the
inversion
of the
flip
flop
output.
For
this
reason,
C33
charging
current
stops
flow-
Ing
to
TRS
base
and
turns
TRS
OFF.
When
TRS
is
turned
OFF
in
either
case,
electric
current
is
not
supplied
to
Supply
Reel
Motor
and
the
rotation
stops.
tape is pulled slightly in both directions by this
circuit.
Electric
current
are
supplied
to
the
two
reel
motors
for
slight
torques,
2)
When
the
tape
is
not
loaded,
TR23
is
ON
and
D22
anode,
through
052
connected
to
the
collector,
is
ground
potential.
TR8
is
therefore
OFF.
When the tape is loaded, TR23 is turned OFF. The
charging
current
of
C34
flows
(R101
>
C34
>
R105
>
TR24)
and
TR24
base
electric
potential
increases
to
turn
ON.
Through
collector
connected
D79,
D22
anode
becomes
ground
potential.
Con-
sequently,
TR8
maintains
OFF
condition.
During
this
time
tape
slack
is
taken
up.
3)
After
C34
is
charged,
TR24
is
turned
OFF
and
bias
is
supplied
to
TR8
base
through
R40
and
D22
from
5V
Line.
TR8
is
thereby
turned
ON
and
causes
D19
cathode
electric
potential
to
decrease.
TR6
base
electric
potential
is
then
decreased
through
R32
and
D14.
At
the
same
time,
TR10
base
electric
potential
is
decreased
through
R38
and
021
so
that
TR6
and
TRIO
аге
turned
ON.
As
a
result,
the
Supply
Reel
Motor
and
the
Take-
up
Reel
Motor
rotate
from
the
electric
current
supplied
through
R27,
TR6
and
R21,
ТК10
respectively.
Since
the
torques
are
toward
pulling
the
tape
at
both
ends,
tape
is
at
a
standstill.
4)
At
Play
mode,
IC4
output
terminal
©
is
at
a
low
level
so
that
D22
anode
electric
potential
decreases
through
D58,
and
TR8
is
turned
OFF.
At
Fast
Forward
and
Rewind
mode,
TR18
is
turned
ON.
D22
anode
becomes
ground
potential
through
055,
and
TR8
turned
OFF.
Thus,
tape
slack
is
prevented
at
Stop
mode
by
a
parking
brake
from
the
weak
torques.
11