4-20.
RECORD
LOGIC
FLIP-FLOP
Transistors
Q8
and
Q9
form
a
bistable
multivibrator
(flip-flop)
which
enable the record
electronics
in the record
mode
and
disable
the record
electronics
at
all
other
times.
The
two
states
of the
flip-flop
are
Q9
conducting,
Q8
off
or
Q8
conducting,
Q9
off.
When
Q8
is
off
the
collector
is
not drawing
current
and
is
at
a
18
VDC
level.
This voltage
is
carried
through
R40
to
the base of
Q9
to hold
Q9
in
full
conduction. Likewise
when
Q9
is
off,
the voltage
from
its
collector
goes to the base of
Q8
through
R41
to hold
Q8
in
full
conduction.
The
flip-flop
will change
state
when
a
positive
voltage
is
applied
to the base of the nonconducting
transistor.
This
is
accomplished through
coupling
resistors
R43
and
R69.
Capacitors
C16
and
C17
prevent
false
triggering
by
shunting
short
duration pulses.
Resistor
R42
sets
the
flip-flop
to stop (not-record)
when
power
is
first
applied.
When
the record switch
is
depressed, a
positive
pulse
is
delivered
to
R45.
If
the
unit
is
in the
RUN
mode
this
pulse will ground through
CR15
to the
RUN
logic
on
the
Power
Supply Board.
If
the
unit
is
in the
STOP
mode
the pulse will
be
conducted through
CR14
to
set
the
flip-flop
to record
(Q8
conducting).
With
Q9
off
Q13
turns
on
to supply a ground to the record
indicator
lamp
and
the
program
record
circuitry
on
the
Record
Amplifier/Bias
Board.
When
the
STOP
switch, 1
kHz
(or 3
kHz)
cue
sensor, or the deck
microswitch
(if
the
cartridge
is
withdrawn) supply a
positive
pulse to
R69,
Q9
will begin to conduct
and
Q8
will turn
off.
The
base of
Q12
will
go
high
to supply a ground
to
the
flip-flop
record
interlock.
Transistor
Q13
turns
off
to
remove
the grounds to the record
lamp
and
program
control.
4-21.
ONE
KILOHERTZ
STOP
CUE
GENERATOR
AND
CONTROL
The
stop cue tone generator
is
composed
of
IC-2A
and
IC-2B
which
oscillates
at
1
kHz
as determined
by
R11, R58, R59,
C14
and
C15.
The
generator
oscillates
when
positive
feedback
is
available
through
R48
and
R49.
The
output of the generator
is
taken through
R55,
C18,
level control
R6,
R46,
and
C12
to
Q5.
This
emitter
follower stage
acts
as a
current
source to drive
the
cue
record head.
The
cue output
is
taken
from
terminal 7 to the
Record
Amplifier/Bias Board.
The
1
kHz
generator
is
controlled
automatically to record a stop
cue
tone
burst
when
the
unit
first
starts
in the record
mode.
This control
is
accomplished
by
IC-2C
and
IC-2D
which
are comparators in cascade to
form
a
mono
stable
multivibrator.
A
12
VDC
reference
is
supplied to
IC-2C
and
IC-20
through
R64
and
R66
from
voltage
divider
R60
and
R61.
The
output of
the
multivibrator
will
go
high only
when
the input
from
R62
goes high.
A
positive
24
VDC
is
ON
position.
(The
OFF
position
without recording a stop tone.
example.)
available
on
S1.
Normally
S1
is
set
to the
allows
starting
the
unit
in the record
mode
This might
be
required in
editing,
for
20
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