Realistic STA-78 - FM RF and IF Alignment

FM RF
&
IF ALIGNMENT
EOUIPMENT
REOUIRED
1.
FM
Signal
Generator
2.
AC Voltmeter
3.
Oscilloscope
4. Distortion
Meter
5.
CenterTuning
Meter
(1.2K
ohm,200pA)
Note:
"Signal
Generator
output should be
no higher than necessary to obtain an
output
reading.
*Maintain
line voltage
at 120
volts,
60
Hz AC
(U
L
&
CSA)
(240
volts,
50
Hz AC
for
Australian
models).
"Set
SELECTOR
Switch to
FM.
"Refer
to
P.C.B.
illustration
and
Figure 7
for
test
points/adjustments.
STEP
GENERATOR
COUPLING
GENERATOR
FREOUENCY
D!AL
SETTING
INDICATOR ADJUSTMENT
REMARKS
1
Signal
Generator
to
FM
Antenna
Termi-
nal thru
FM
Dummy
Antenna
(300
ohm)
98
MHz
(400
Hz
75 kHz dev.)
lnput:
about
2-3
ttY
Near
98
MHz
AC Voltmeter.
Scope
and
Dis-
tortion
meter
to
TAPE
OUT
Jack
(L
or
R).
T101
Adjust for maximum
reading on
meter.
Refer
to
Figure
1 1.
2
Same as STEP 1
98
MHz
(400
Hz,
75 kHz dev.)
lnput: no
input
(unit
off
)
Near
98
MHz
Connect the
Center Tuning
Meter
(1.2
kO,
200
pA)
to
Pin
No.12(+)and
No.13(-)on
AM/FM IF
Board
(Refer
to
Figures
7
and 9A.)
T201
(Primary)
Adjust
for
Center
point
on Center
Tu-
ning Meter.
Refer
to
Figures
9,
9A,
10 and 1 1.
3
Same as
STEP
1
98
MHz
(4OO
Hz,
75 kHz dev.)
lnput:
1
mV
Same
as
STEP
1.
AC Voltmeter,
Scope and
Dis-
tortion
Meter
to TAPE OUT
Jack
(L
or
R).
T201
(Secondary)
Adjust for minimum
Distortion
(about
0.1%).
Refer
to
Figure
9,
10
and
1 1.
4
Repeat
STEPs 1
,2
and
3 until no further improvement is noticed.
5
Same as STEP 1.
90
MHz
(40O
Hz,
75
kHz,
dev.)
lnput:
about
2-3
ttY
90 MHz
Same as
STEP
1.
L101
(FM
Antenna Coil)
1103
(FM
RF
Coil-stretch
or
squeeze)
Ll05
(FM
OSC
Coil)
Adjust for
maximum
reading
on
meter.
Refer
to
Figures
7
and
1 1.
b
Same as STEP 106
MHz
(400
Hz,
75 kHz dev.)
lnput:
about
2-3
ttY
106
MHz
Same
as
STEP 1.
TC
101(FM
Antenna
Trim-
mer)
TC1O2
(FM
RF
Trimmer)
TCl03
(FM
OSC
Trimmer)
Adjust
for maximum
reading on
meter.
Refer
to
Figures
7
and 1 1.
7
Repeat
STEPs 5 and 6
until no further improvement is noticed.
8
Same as STEP 1
98
MHz
(400
Hz,
75 kHz dev.)
lnput:
5
trrV
98
MHz Same as
STEP
1.
VR2O3
"MUTE"
switched
"ON"
and
adjust
VR203
for no
signal
output.
I
Same as
STEP
1
98
MHz
(4OO
Hz,
75
kHz
dev.)
lnput:
100
mV
98
MHz
Signal
Meter
on Set.
vR202
Adjust
so
the
Meter
Pointer
on
Receiver is
about
90%
of
full-scale.
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