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Akai 1700 Service Manual

Akai 1700
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W
ADJUSTMENT
OF
AMPLIFIER
1.
ADJUSTMENT
OF
RECORDING
BIAS
FREQUENCY
Recording/erasing
bias
frequency
was
sct
at
90
KG
plus
or
minus
5KC
before
shipment.
It
is
decided
by
inductance
of
the
oscillator
coil
(part
#17-L:)
and
its
resonant
capacitor
{part
C-17),
To
measure
recording
bias
frequency,
insert
a
10
or
100
ohm
resistor
in
series
to
the
record/play
head
and
connect
vertical
input
terminals
of
an
oscilloscope
as
shown
in
the
Fig.
13.
Another
testing
instrument
to
be
prepared
is
an
audio
frequency
oscillator
and
its
output
should
be
conne-
cted
to
horizontal
input
terminals
of
the
oscilloscope.
Vary
frequency
generated
by
the
audio
frequency
oscillator
around
90
KC,
and
set
the
oscillator
at
the
point
where
a
desirous
figure
appears
on
the
oscilloscope.
The
recording
bias
frequency
now
corresponds
to
the
reading
of
the
oscillator.
Check
oscillator
coil,
C-17
and
bias
head
if
the
recording
bias
frequency
measured
is
not
within
90KG
+
5KG,
2.
ADJUSTMENT
OF
RECORDING
BIAS
VOLTAGE
A
proper
recording
bias
voltage
is
45
volts
+
3
volts
A.C.
and
is
adjusted
by
Cl6,
To
measure
recording
bias
voltage,
connect
a
V.T.V.M.
(Vacuum
Tube
Volt
Meter)
to
the
record
[play
head
as
shown
in
the
Fig.
14.
Check
C16
{included
AK
13)
and
record/play
head
if
the
recording
bias
voltage
measured
does
not
meet
to
the
above-
mentioned
specification.
PAL)
JL)
FC,
100P:
V.T.VM.
{
ais
[tos
PAIR)
a
C,
,100P
FY
wean
elo
P,{L)
K+
oscittaton
©.
1OORF
Wt
OSCILLOSCOPE
AUDIO
FREQUENCY
‘OSCLOATOR
Fig.
13
L,(0.8.C)
tc
V,(P)(LEFT)
=
V,(G,)
RIGHT)
B+
EC,
100PF~
EE
VAG,
)LEFT)
sa
V,(P)RIGHT)
3.
ADJUSTMENT
OF
ERASING
BIAS
VOLTAGE
A
proper
erasing
bias
voltage
is
65
volts
+
5
volts
A.C.
and
is
adjusted
by
C14.
To
measure
erasing
bias
voltage,
connect
a
V.T.V.M.
to
the
erase
head
as
shown
in
the
Fig.
15.
Check
C4
and
erase
head
if
the
erasing
bias
voltage
measured
does
not
meet
to
the
above-mentioned
specification.
J,{L)
C,,150PF}
4
E.
HEAD,
P{R)
J,(R}
C.A50PF)
Fig,
14
P,(L)
J,(L)
C,.
100PF
pai
PAR)
J,(R}
C..100PF
L,(0.8.C)
at
V,(P)(LEFT)
P,
HEAD
a
me
B+
Ee
tigger
VG:
(RIGHT)
PL)
J,(L)
C,,150PF]
=
V(G,)
(LEFT)
Cis
V,(P)(RIGHT)
E
wea
Ee?
IF
P,(R)
J,(R)
C,,150PF]
ee
————%
+
V.T.V.M
Fig.
15
4,
ADJUSTMENT
OF
RECORDING
LEVEL
A
basic
recording
level,
referred
to
as
“0
VU”,
set
at
the
point
where
current
of
30zA
4
10%
flows
to
the
recording
head
at
1,000
cycles.
The
VU
meter
indicates
0VU
+
2VU
when
a
signal
of
—55db
+
5db
eets
at
the
microphone
jack
or
—40
db
+
5db
at
the
line
input
jack
when
a
the
volume
control
set
at
its
maximum.
®@
Adjustment
of
recording
level
can
be
accomplished
by
varying
sensi-
tear
art
|
town
Reon
|
ea
I
tivity
of
VU
meter,
however,
it
is
not
necessary
to
make
in
a
field
of
oo
ashi)
service
as
all
VU
meters
have
correctly
been
calibrated
at
factory
before
?
shipment.
(See
Fig.
16
for
details.)
arent)
=
OMELET
LA?
NOTE:
Make
sure
to
stop
oscillation
by
disconnecting
the
oscillator
coil
#
17-L;
at
the
points
marked
“P”
and
“G”
prior
to
measure-
ment
of
recording
level.
—w-—
Fig.
16

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Akai 1700 Specifications

General IconGeneral
BrandAkai
Model1700
CategoryTape Deck
LanguageEnglish

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