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For
the
radio
Caution:
(high
frequency)
circuit,
refer
to
"GENERAL
ALIGNMENT
INSTRUCITON"
in the
GF-777H
Service
Manual
ELECTRICAL
ADJUSTMENT
e
Record
Amplifier
Bias
Current
Adjustment
and
Bias
Oscillator Frequency
Check
1) Make
connection
of instruments
as shown
in Fig.14—1.
2) Set the mode selector switch at ''tape", the tape selector
switch
at ''normal',
the beat cancel
switch
at "A" and
the
record
level
control
knob
at 10
(max.)'' position.
3) Place the unit in record mode. Adjust the coil (L203 or
L204)
so
that
the
electronic
voltmeter
reads
45mV:
with
the
tape
selector
switch
at "metal"
position,
also
adjust so that the reading is 88
+ 3mvV.
4) Check
that the frequency
counter reading available then
is 86 + 3kHz. If not, adjust the bias oscillator coil (L205)
and
readjust the bias current
in step 3) above.
(See to Table 14—1.)
e
Erase Current Check
1) Make
connection
of instruments
as shown
in Fig.14—2.
2) Set the tape selector switch
at ''metal"
position.
3) Place the unit in record mode, and see that the electronic
voltmeter
reading is 120
+ 40 mV.
With the tape selector switch changed to ''normal"' position,
see that the electronic voltmeter reading is 60 + 20 mV.
e
VU
Meter Sensitivity Adjustment
3) Set the mode selector switch at "tape'', the record mode
selector
switch
at ''manual'"'
and the Dolby
NR
switch
at "off"
position.
R207 or R208
recctalmeveack oscilloscope
sre
electronic
frequency
voltmeter
counter
Figure
14—1
Beat Cancel
Switch
Oscillation
Frequency
86 +
3kHz
89
81
Table 14—1
record mode
erase head
oscilloscope
electronic
voltmeter
Figure
14—2
record/playback
cide ial eu
external mic Den
'
_
jack
a a
electronic oscilloscope
03,48
in
(Rec
2°8 2
J303 (L-ch)
Fenatd
voltmeter
audio generator
J304 (R-ch)
mode
attenuator
$0301
@) Pin (GND)
Figure 14—3
—14—
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