Sony ST-88 - FM Alignment: Frequency and Tracking; Frequency and Tracking Alignment Procedures; FM Frequency Alignment Test Equipment and Preparation; FM Frequency Alignment Methods

Procedure:
1.
With
the
equipment
connected
as
shown
in
Fig.
3-5,
set
the
signal-generator
controls
as
follows:
Frequency........
Specified
frequency
of
ceramic
filter.
See
Table
3-1.
Modulation
.......
Fm,
400
Hz,
100
%
(75
kHz)
Output
level.......
1,000
nV
(60
dB)
2.
Set
the
tuner
switches
as
follows:
BAND
switch......
FM
MODE
switch......
MONO
AFC
switch
.......
OFF
3.
Adjust
the
signal
generator
frequency
slightly
to
obtain
a
maximum
output,
and
then
change
the
signal
generator
modulation
to
a-m,
400
Hz
30
%.
4.
If
the
discriminator
transformer
IFT201
is
not
aligned
correctly,
400
Hz
ripple
will
be
observed
as
shown
in
Fig.
3-6.
5.
Turn
the
secondary
side
core
(green)
of
discrimina-
tor
transformer
IFT201
(see
Fig.
3-10)
with
an
alignment
tool
to
obtain
a
minimum
indication
on
the
oscilloscope
as
shown
in
Fig.
3-6.
Fig.
3-6.
Fm
discriminator
alignment
output
response
Note:
Turn
the
core
carefully
and
slowly
because
the
output
appearing
on
the
oscilloscope
jumps
up
and
down
when
turning
the
core.
This
might
cause
diffi-
culty
in
determining
the
point
of
mini-
mum
output.
Also,
at
both
extreme
positions
of
the
top
core,
decreased
out-
put
will
be
observed.
The
real
null
point
should
be
obtained
in
the
middle
of
the
rf
eae
signal
Cv102
generator
=
OQ-—-__~__—____—__.
R229 |
core
thread
length,
and
maximum
output
occurs
at
each
side
of
the
true
null
point.
6.
Change
the
signal
generator
modulation
to
fm,
400
Hz
100
%.
7.
Turn
the
core
of
fm
IFT101
and
primary
side
core
(brown)
of
discriminator
transformer
IFT201
(see
Fig.
3-10)
to
obtain
the
maximum
output.
3-2.
FM
FREQUENCY
COVERAGE
AND
TRACKING
ALIGNMENT
Note:
Before
starting
this
alignment,
the
fm
i-f
and
discriminator
alignment
should
be
performed.
Test
Equipment
Required
1.
Fm
signal
generator
2. Ac VTVM
3. Oscilloscope
4. Alignment tools
Preparation:
1.
Connect
the
equipment
as
shown
in
Fig.
3-7.
2.
Set
the
tuner
switches
as
follows:
BAND
switch...
...
FM
MODE
switch.
.....
MONO
AFC
switch...
2...
OFF
Signal
Generator
Method
Follow
the
procedures
given
in
Table
3-2
when
performing
this
alignment
with
an
fm
signal
generator.
Be
sure
that
the
dial
is
mechanically
calibrated.
Off-the-Air Signal Method
Accurate
dial
calibration,
and
a
frequency
cover-
age
test
can
also
be
performed
by
utilizing
off-the-air
local
fm
signals.
However,
before
performing
the
following
procedure,
be
sure
that
the
dial
is
mechani-
cally
calibrated.
oscilloscope
PAA
Fig.
3-5.
Fmi-f
and
discriminator
alignment
test
setup
by
rf
signal
generator