NAD 402 - AM Tuner Alignment

G. AUTOSEARCH LEVEL
1.
Turn
R48
fully
clockwise
and
R48A
fully
counterclockwise.
Set
stereo
modulator
to
L=-R
mode
and
apply
98MHz
(18dBu)
to
antenna
input.
Adjust
R48
counterclockwise
until
center
tune
LED
lights
up.
OF ON
Check
if
autosearch
operation
is
«working
properly
at
antenna
input
level
of
28dBu.
Center
tune
LED
should
be
at
least
2dBu
higher
than
FM
stereo
LED.
H.
STEREO
SEPARATION
AND
PILOT
SUPPRESSION
1.
Modulate
L-only
at
98MHz
(60dBu)
and
adjust
R62
for
minimum
output
on
right
channel.
2.
Modulate
R-only
and
adiust
R62
for
minimum
output
on
left
channel.
3.
Repeat
(1)
and
(2)
until
readings
are
the
same
and
within
specification.
4.
Turn
off
modulating
signal
but
leave
pilot
tone.
5.
Adjust
FL401
and
FL402
for
minimum
output
on
left
and
right
channels,
respectively.
AM
SECTION
A.
PREPARATION
1.
Set
signal
generator
to
AM
mode
with
1kHz
at
30%
modulation.
2.
Connect
22pF
ceramic
capacitor
between
signal
generator
and
AM
antenna
input
terminal.
Capacitor
should
be
as
close
as
possible
to
antenna
input
terminal.
3.
Store
the
following
frequencies:
603/600kHz,
999/1000kHz,
and
1404/1400kHz.
B.
OSCILLATOR
TUNING
VOLTAGE
1.
Connect
DVM
between
TP6
and
ground.
2.
Tune
to
603/600kHz
and
adjust
L6
for
1.75VDC
+50mV
reading
on
DVM.
C.
LF.
1.
Apply
999/1000kHz
(45dBu)
to
antenna
input.
2.
Tune
to
999/1000kHz
and
adjust
L7
for
maximum
reading
on
audio
output.
D.
R.F.
1.
Apply
603/600kHz
(45dBu)
to
antenna
input.
2.
Tune
to
603/600kHz
and
adjust
L5
for
maximum
reading
on
audio
output.
3.
Apply
1404/1400kHz
(45dBu)
to
antenna
input.
4.
Tune
to
1404/1400kHz
adjust
C26
for
maximum
reading
on
audio
output.
5.
Repeat
(1)
to
(4)
until
no
further
improvement
can
be
made.
TPS
R62
FL402
FL401
(VB)
18
LO
C16
TP6
® e
s ise
RASS
LEA
TPS R48A RABEL? C26 TP4 i L6
(LEVEL) (vA)
TUNER ADJUSTMENT POINTS
5.
Increase
antenna
input
signal
to
22dBu
and
adjust
R48A
clockwise
until
FM
stereo
LED
lights
up.
]
;