Akai 1700 Service Manual

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

Akai 1700 Specifications

General

Brand	Akai
Model	1700
Category	Tape Deck
Language	English