EasyManua.ls Logo

3M DELTA Series - Cue Tone Generation; Head Control; Cue Tone Detector

3M DELTA Series
110 pages
Print Icon
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Loading...
further
signal
conditioning
and
ultimately
to
the
record
heads
Cue
Tone
Generation
The
ALE
frequency
fed
to
U1204
pin
1
(as
above)
is
divided
by
16
and
output
at
U1204
pin
6
at
a
fre
quency
of
14,914
Hz,
This
is
fed
to
U1205
pin
4,
and
routed
through
two
sequential
divide-by-ten
circuits.
This
divide-by-
100
outputs
a
square
wave
on
Pin
13,
U1205,
at
a
frequency
of
149.14
Hz.
It
is
routed
to
U1206B
pin
4.
The
processor
logic
line
(low
during
150
Hz
tone
generation)
is
fed
to
pin
5
of
U1206.
When
the
processor
logic
is
"low"
on
pin
5,
U1206B
pin
6
outputs
the
149.14
Hz
square
wave
into
U
1
209C.
U1209C
and
D
comprise
a
4-pole
low
pass
filter
with
an
approximate
24
db
per
decade
slope.
This
filter
sharply
attenuates
the
"harmonic"
content
of
the
square
wave
so
that
the
output,
pin
14
of
U1209D
is
a
virtual
sine
wave.
This
signal
is
AC
coupled
to
U1208A
which
is
a
variable
gain
buffer/mixer
and
provides
"audio"
to
the
cue
circuits
on
the
bias
board.
1
kHz
and
8
kHz
cue
tones
are
generated
in
a
similar
manner.
The
ALE
signal
238.6
kHz,
is
routed
to
U1203
pin
6,
a
divide
by
15.
The
output,
15.909
Hz,
is
routed
to
U1204
pin
13.
which
outputs
a
7954.5
Hz
after
a
divide
by
two,
and
a
994,3
Hz
after
a
divide
by
16.
These,
of
course,
become
the
8
kHz,
and
1
kHz
cue
tones
after
appropriate
filtering.
The
control
of
these
tones
is
provided
by
processor
ports
on
U
1201,
pins
37,
and
35
and
are
"gated"
on-or
off
by
the
processor.
All
three
cue
tones
are
actively
mixed
at
the
input
of
U1208A.
R1231,
located
in
the
U1208A
feedback
circuit,
is
used
to
adjust
the
Master
cue
tone
levels.
The
proper
level
relationship
between
the
three
cue
tones
is
set
by
fixed
resistors
An
"extra"
input
to
the
cue
audio
circuit
is
provided
via
a
rear
panel
connector
pin
so
that
external
sources,
such
as
F.S.K.
generators
may
be
connected
to
the
Delta
IV
Record
Amplifier.
This
audio
is
AC
coupled
through
Cl
223
and
mixed
with
the
other
cue
signals
at
the
input
of
U
1
208A
Head
Control
The
record
processor
executes
an
electronic
on
or
off
for
the
program
and
cue
record
heads.
This
is
done
to
minimize
any
bias
turn
on
or
turn
off
tran
sients
being
introduced
onto
tape.
The
logic
lines
are
pins
23
and
24
of
U1201
and
they
go
"low"
to
turn
on
their
respective
tracks.
These
logic
lines
are
connected
to
the
output
of
the
bias
amplifier
circuit,
where
the
head
control
transistors
are
located.
E.
CUE
TONE
DETECTOR
The
digital
cue
tone
detector
is
located
on
the
reproduce
amplifier
board.
The
detector
system
con
sists
of
an
equalized
preamplifier,
a
fixed
gain
buffer
stage,
four
band-pass
filters,
a
microprocessor,
logic
outputs
to
the
relay
drivers,
and
logic
outputs
to
the
transport
control
microprocessor.
Audio
from
the
play
head
cue
track
is
fed
into
a
high
gain
fixed
equalization
preamplifier,
U108.
It
is
coupled
to
the
second
half
of
U
108,
which
increases
signal
level
and
drives
the
four
band-pass
filters.
Three
of
these
filters
are
center-tuned
for
the
NAB
cue
tone
frequencies
of
1
kHz,
150
Hz.
and
8
kHz.
A
fourth
section
is
band-tuned
to
3
kHz
and
is
used
to
detect
the
1
kHz
cue
tone
when
the
deck
is
in
“
High
Speed."
Each
filter
outputs
one
of
four
sections
to
component
U
110.
These
squaring
circuits
in
turn
are
routed
to
separate
inputs
of
the
microprocessor.
Pro
grams
in
the
cue
detect
microprocessor
contain
the
necessary
memory
routines
to
"measure"
the
fre
quency
of
the
incoming
signals
from
the
squaring
circuits.
Depending
on
the
frequency,
the
cue
detect
microprocessor
outputs
logic
"1"
or
logic
"0"
to
the
appropriate
support
devices
Logic
outputs
from
the
cue
detect
microproces
sor
drive
the
transport
logic
(1
kHz
and
3
kHz
tones),
and
the
output
peripheral
drivers
(150
Hz
and
8
kHz
tones).
U1
12
provides
the
drive
for
150
Hz
and
8
kHz
relays.
Logic
(for
EOM
signaling)
and
1
kHz
''STOP'
outputs
directly
from
microprocessor
U
111.
A
user
selectable
jumper
enables
either,
neither,
or
both
the
150
Hz
and
8
kHz
cue
tones
to
engage
the
End
of
Message
(EOM)
sequence.
This
consists
of:
1)
muting
the
audio;
2)
switching
the
motor
to
high
speed;
and
3)
enabling
the
3
kHz
cue
detector
via
a
processor
input
(low)
at
pin
13
of
the
card
edge
connector.
Jumpers
are
used
to
provide
an
open
collector
output
(to
ground)
upon
detection
of
the
150
Hz
or
8
kHz
cue
tones.
F.
MOTOR
CONTROL
AND
MOTOR
The
motor
and
motor
control
circuits
comprise
a
high
precision
crystal
referenced
electro-mechani
cal
tape
drive
system.
The
motor
circuits
are
mount
ed
on
a
small
printed
circuit
board
adjacent
to
the
motor.
The
motor
is
DC
operated.
It
has
an
integral
120
pole
tachometer
and
tachometer
ring
located
inside
the
bottom
of
the
rotor.
There
are
3
Hall-effect
sen
sors
located
mechanically
120
degrees
apart.
They
are
used
for
sensing
the
rotating
position
of
the
rotor/shaft,
and
a
3-phase
Y
connected
stator.
Con
nection
to
the
control
circuit
is
via
a
multiple
con
ductor
mass-termination
type
connector,
which
pro
vides
all
operating
DC
voltages
and
signals.
6-4

Table of Contents

Related product manuals