Sharp SG-315H - TAPE DECK CIRCUIT ADJUSTMENTS; Bias Oscillator and Head Alignment; ALC Characteristic Calibration

TAPE
DECK
CIRCUIT
ADJUSTMENT
®
RECORD
AMPLIFIER
BIAS
OSCILLATOR
ADJUSTMENT
(Refer
to
Figure
6)
1.
As
shown
in
figure
6,
connect
the
VTVM
across
the
resistors
of
100
ohm
(R809,
R810).
2.
Set
the
unit
in
“RECORD”
mode
and
RIF
switch
in
upper
position.
3.
Then,
connect
the
frequency
counter
to
the
output
terminal
of
VTVM
and
adjust
the
oscillator
coil
(L805)
so
that
the
bias
oscillation
frequency
becomes
53.5
kHz.
4.
Adjust
the
variable
resistors
(VR801,
VR802)
so
that
the
VIVM
readings
becomes
60
mV.
RECORD/
PLAYBACK vy T.V.M
Oscillosco
HEAD = ig
RECORD Mode
Frequency
Counter
Figure 6
@ RECORD/PLAYBACK HEAD AZIMUTH ADJUSTMENT (Refer to Figure 7).
1.
Connect
4.ohm
dummy
resistor
to
the
speaker
output
terminals
(SO504
or
SOS505)
and
connect
the
VTVM
across
the
resistor.
2.
Playback
the
test
tape
(TEAC
MTT-114;
250
PWB/mm,
—10
dB,
10
kHz).
3.
Rotate
the
adjusting
screw
so
that
the
playback
output
voltage
becomes
maximum
in
both
channels.
Figure 7
™ ALC CHARACTERISTIC ADJUSTMENT (Refer to Figure 8)
.
Connect
a
33MFD
electrolytic
capacitor
across
both
terminals
of
the
erase
head
to
stop
the
bias
oscillation.
. Set the unit in record mode.
.
As
shown
in
figure
8,
connect
the
VITVM
across
100
ohm
resistors
(R809,
R810).
. Rotate the variable resistor (VR803) to its mechanical center position.
.
Input
1
kHz,
—70
dB
and
—40
dB
signals
to
microphone
jacks
(J502,
J503).
.
Adjust
the
variable
resistor
so
that
the
difference
of
the
reading
on
VTVM
for
—70
dB
and
—40
dB
becomes
4+
3
dB
at
each
channel
and
the
difference
for
left
and
right
channel
becomes
less
than
3
dB.
Dun WN
1
R/P HEAD
SIGNAL
GENERATOR RECORD
MICROPHONE ibe
JACK (502,503)
Figure 8
6