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Fostex A-8 - Page 14

Fostex A-8
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The
signals
from
U6-1
(Q
output)
and
U9-14
(REC-0
output)
passing
through
the
OR
gate
of
D41
and
040
is
applied
to
the
base
of
Q8
to
switch
it
on
if
either
of
the
above
signals
are
of
"H"
level,
and
thus
an
"L"
level
representing
the
trans
port
record
signal
is
applied
to
the
RECORD
TRACK
selector
circuit.
4.4
CAPSTAN
MOTOR
DRIVE
CIRCUITS
If
the
recorder
is
switched
on
with
the
tape
loaded
(with
the
left/right
ten
sion
arm
in
the
up
position)
,
the
capstan
motor
begins
to
rotate
at
1,000
rpm,
and
when
put
in
the
play
mode,
accelerates
to
2,000
rpm.
Q18
is
in
the
on
state
when
power
is
switched
on
and
this
raises
the
DC
level
of
Ull-1
which
then
switches
on
Q19
to
start
the
motor.
The
1,
200Hz
output
from
the
TACH
generator
applied
to
Ull-14
is
amplified
and
a
square
wave
is
output
from
its
pin
#14.
This
square
wave
is
differentiated
by
C25,
R90,
R91
and
the
plus
side
of
this
waveform
switches
on
Q16.
When
the
recorder
is
switched
on,
U8-1
goes
to
"L"
,
QI
4
and
QI
5
switches
on
and
this
output
is
applied
to
the
integration
circuit
of
R92,
R93
and
C47/C48.
Therefore,
a
sawtooth
waveform
made
by
the
signal
from
the
integration
circuit
and
on/off
action
of
Q16,
is
applied
to
comparator
Ull-8.
The
rectified
output
from
the
integration
circuit
of
R98,
R99
and
C27
passes
through
Q18
and
DC
amplifier
Ull-1
and
applied
to
Q19
which
controls
the
current
to
the
capstan
motor.
Fig.
4-4
14

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