NAD 7250PE - Page 11

6
Increase
FM
generator
level
upwards
from
O
and
adjust
R
167
‘ST
SW”
so
that
stereo
light
turns
on
and
audio
outputs,
as
watched
on
VTVM’s
and
oscilloscope,
switches
to
one
channel
only
at
10
uV
input
level.
TOLERANCE +5 uv
NOTE:
When
turning
input
level
down
the
unit
will
switch
into
mono
at
a
lower
level,
typically
7
UV.
7
Stereo
separation.
Set
FM
generator
output
to
1000
uV,
modulate
left
channel
only.
8
Adjust
R
158
for
minimum
on
right
channel
VTVM.
Modulate
FM
generator
right
channel
only
and
adjust
R
158
for
minimum
on
left
channel
VTVM.
10
If
the
minimum
in
step
8
and
9
are
different,
adjust
R
158
so
that
the
readings
are
the
same
in
both
channels.
SPECIFICATION
better
than
50
dB
separation
11.
MPX
filter
Turn
off
audiomodulation,
leaving
pilot
tone
only.
Disable
IHF
filter,
or
external
19
kHz
filter.
12
Check
19/38
kHz
suppression.
SPECIFICATION
more
than
60
dB
13
If
unit
does
not
meet
specification
adjust
FL
102
‘“MPX
FILTER”
on
left
channel
and
FL
103
“MPX
FILTER”
on
right
channel
to
minimum
output.
NOTE:
DO
NOT
ADJUST
THE
MPX
FILTERS
UNLESS
NECESSARY,
the
cores
are
brittle
and
break easily.
14
Release
the
FM
NR
DEFEAT
switch
(out).
FM NR CIRCUIT
Confirm
that
FM
NR
switch
is
set
to
OFF
position
at
first.
1
Feed
from
SG
to
the
antenna
input
125
uV
(300
ohms),
98.00
MHz
with
100%
stereo
modulation,
and
set
reference
for
S/N
measurement.
With
reference
set,
cancell
the
stereo
modulation
of
98.00
MHz
and
confirm
that
S/N
ratio
at
this
stage
reads
—60
dB
approx.
Switch
FM
NR
on,
and
adjust
R-230
so
that
S/N
is
improved
by
2
dB.
3
Switch
FM NR
off,
and
feed
40
uV
of
98.00
MHz
with
100%
stereo
modulation
to
set
reference
for
S/N.
LS)
Cancell
stereo
modulation
and
confirm
that
S/N
at
this
stage
reads
—50
cB.
4
Switch
FM
NR
on,
and
confirm
that
S/N
ratio
is
improved
by
5
-
13
dB.
SYNTHESIZER FREQUENCY
1
Tune
to
a
known
accurate
frequency
source,
i.e.,
broadcasting
station
or
synthesized/digital
display
FM
generator
preferably
in
the
midband
95
-
100
MHz.
Connect
DMM
across
TP
104
(negative)
and
TP
105
(positive).
Adjust
C
209
‘’FQ”’
so
that
DMM
reads
the
same
as
recorded
in
E
—
7.
TOLERANCE
+10
mV
W DN
10