In
the
ON
position
+24
VDC
is
applied to
R29.
If
the record logic
is
not
set
for
record, the voltage will ground through
CRS
to
Q12.
Similarly,
the voltage will ground to the 1
kHz
record
interlock
through
CR9
if
the
unit
is
in the stop
mode
(tape not running).
If
these conditions are
met
the
voltage will
be
applied through
CR7
and
CRIB
to
IC-2C.
This causes
IC-2C
to
go
high;
this
is
carried
through
C28
and
R63
to send
IC-2D
high.
When
C28
charges
fully,
the
de
path to
IC-2D
is
blocked.
The
output of
IC-2D
goes
low
and
remains
low
until
IC-2C
is
unlatched
and
relatched.
When
the
multivibrator
goes high,
this
voltage
is
supplied through
CR17
and
CR24
to the cue bias switching
circuit
on
the
Record
Amplifier/Bias
Board. This turns
on
the recording bias
to
the cue
track.
The
output of the
multivibrator
also turns
on
the 1
kHz
generator
by
turning
on
FET
QlO.
Voltage
is
applied to the gate of
QlO
through
R67
but
is
shunted
to
ground
through
CR20
and
R68.
The
age
is
applied to the gate of
QlO
through
R67
but
is
shunted to ground through
CR20
and
R68.
The
FET
is
held nonconducting
and
the generator
is
held
off.
When
the
multivibrator
goes high,
CR20
is
back
biased through
CR16
to allow
QlO
to
turn on.
When
the
multivibrator
goes low,
QlO
turns
off
and
shuts
down
the generator. Since the
multivibrator
has
a
time constant of approximately three
quarters
second, a stop tone
burst
that
length
is
recorded
on
the cue
track.
4-22.
AUXILIARY
CUE
TONE
GENERATORS
AND
CONTROL
When
the optional Q-Trips
are
installed,
150Hz
and
8kHz generators
which
are
similar
in operation to the 1
kHz
generator are employed. These
are
two
stage operational
amplifier
oscillators,
]C-3A-
IC-3B
(150Hz),
IC-3C-
IC-3D
(8
kHz).
The
frequency
is
determined
by
the network
RIO
(Rl2),
R50
(R92),
R51
(R91),
C22
(C24),
and
C23
(C25).
Oscillation
occurs
when
positive
feedback
is
supplied
by
R73
(R93,
R94).
The
output of the generator
is
supplied through the level control
R8
(R7)
to
the cue
head
driver
Q5.
To
permit recording
from
an
external
generator,
the
rear
panel
external cue input
is
connected through a
separate
level control
(R9)
to
Q5.
The
Q-Trip generators are not automatically
controlled
by
the
machine
but manually
by
the
front
panel switches or through a separate
level control connector.
The
FET
in the feedback
circuit,
Qll (Q15),
is
held
off.
The
voltage
on
its
gate
is
shunted through
CR21
(CR22)
and
R82
(R83)
to ground.
When
a
positive
voltage
is
supplied to the Q control
through
CR29
(CR28),
CR21
(CR22)
is
back
biased to allow the
FET
to
turn on.
When
the control goes low, the
FET
is
again shut
off.
When
the Q control
is
high, the voltage
is
also
applied through
CR26
(CR27)
and
CR24
to
the cue bias switch to enable the bias switching
(on
the
Record
Amplifier/Bias Board).
To
supply bias to record
an
external
signal
on
the cue track
positive
voltage
must
be
supplied
from
the remote
control connector through
CR25
to the cue bias switch.
To
permit recording the Q-Trips or
an
external tone in the play-
back
mode,
transistor
Ql4
is
installed.
A
positive
voltage
on
the
150
Hz,
8
kHz,
or external cue
controls
is
coupled through
R5
and
CR23
to the base
of
Q14.
Transistor
Q14
turns
on
to supply a ground to terminal 6
to
turn
on
the bias
oscillator.
The
cue generators run,
and
the cue track receives
bias
from
the bias
oscillator,
so
a cue tone
is
recorded.
The
program
track
is
undisturbed, since the
program
bias
and
audio are not turned on.
21
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