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FM
ALIGNMENT
NECESSARY
INSTRUMENTATION:
* Ke
Ke
**RK
HH
*
Stereo
Modulator
(less
than
0.05%
THD,
more
than
50dB
Sep.)
FM
Generator
(less
than
0.05%
THD)
75
ohm
Dummy
Antenna
(if
needed
by generator)
Audio
Oscillator
(not
necessary
if
FM
generator
has
built-in
sweep,
e.g.,
SOUND
TECHNOLOGY
ST
1000A
or
ST
1020A)
2 AC
VTVM's
(or
one
with
a Left/Right
switch)
THD
Analyzer
(resolution
less
than
0.1%)
Oscilloscope
(5mV
or
better
sensitivity,
X-Y
capability)
Frequency
Counter
Diode
Detector
Probe
Ferrite/Brass
inductor
test
probe
IMPORTANT
NOTES
1)
2)
3)
4)
5)
6)
A.
RF
levels
are
at
antenna
input.
Before
aligning,
select
FM,
switch
off
IF
NARROW
and
MONO.
If
FM
Generator
is
not
synthesizer-type,
be
sure
to
check
its
frequency
with
Frequency
Counter
When
adjusting
detector
and
stereo
decoder
circuits.
Hum
in measurements
may
be
caused
by
ground
loop
via
antenna
cable;
if
so,
use
isolation
balun,
or
isolate
cable
shield
and
hot
with
small
capacitors
(470
~
1000pf).
To
adjust
front-end
coils,
bend
gently
with
wooden
or
plastic
tool
(non-interactive).
ENTER
the
following
frequencies:
90.00,
105.00,
87.50,
108.00,
98.00
LOCAL
OSCILLATOR
FREQUENCY
1.
Connect
Frequency
Counter
between
front-end
pin
8
(front-most)
and
Ground.
2.
Tune
to
90
MHz
(No
RF
input
needed).
3.
Adjust
C-934
so
that
reading
is
100.700MHz
+ 2KHz.
4,
Remove
counter.
TUNING
VOLTAGE
1.
Connect
DMM
between
P-936
and
Ground.
2.
Tune
to
108.00MHz,
and
adjust
L-7
if
reading
is
not
20.0V
+ 0.5V
3.
Tune
to
88.00MHz,
and
check
that
reading
is
3.0V
+ 0.5V
4,
Repeat
until
within
tolerance.
TRACKING
1.
Connect
FM Generator
to
75 ohm
antenna
input
(modulate
+ 150kHz
sweep)
and
Detector
Probe
to Pin
1 of Q106
(ground
to tunershield).
2.
Adjust
vertical
sensitivity
of
Oscilloscope
to
maximum,
and
set
to
X-Y
mode.
(X input
is
sweep
signal,
Y is
detector
probe).
3.
Tune
to
105MHz
and
adjust
generator
so
that
curve
appears
on
Oscilloscope,
and
covers
approximately
1/2
of
display.
4,
Check
L2,
L3,
L4
with
ferrite/brass
probe,
adjust
only
if
probe
cauBes
curve
height
to
increase
more
than
10%.
If
necessary,
Yreduce
generator
output
to. keep
entire
curve
on
display.
9
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