NAD 402 - Alignment Procedures; FM Tuner Alignment

ALIGNMENT PROCEDURE
NOTE:
1.
To
change
AM
steps
from
9kHz
to
10kHz
and
vice
versa,
press
the
MODE
and
SCAN
UP
buttons
simultaneously
for
three
seconds.
2. To reset the presets, press the AM FM and STORE buttons simultaneously for three seconds.
FM SECTION
A. PREPARATION
1. Set stereo modulator to mono mode with 1kHz modulating signal unless otherwise stated.
2. Set signal generator to FM mode with 75kHz deviation.
3. Store the following frequencies: 98MHz, 87.5MHz, 108MHz, 90MHz, and 106MHz.
4. Note: RF levels are open circuit voltages of signal generator with 75 ohms output impedance.
B. OSCILLATOR TUNING VOLTAGE
1. Connect DVM between TP6 and ground.
2. Tune to 87.5MHz and check DVM for a reading of 3VDC +0.5V.
3. Tune to 108MHz and check DVM for a reading of 20.5VDC +0.5V.
if either of the above is out of tolerance, adjust FE4 (oscillator coil) until both readings are
within tolerance.
Connect DVM between TP4 (VA) and TP5 (VB).
Apply 10.7MHz (90dBu) via 1Kohm resistor to TP7.
Adjust L8 for OVDC +50mV reading on DVM.
Adjust L9 until minimum THD is achieved at audio output.
Repeat (3) and (4) until no further improvement can be made.
akwONaE
When
adjusting
L9,
two
nulls
can
be
found.
With
the
core
on
top,
adjust
until
the
second
one
is
found
as
this
has
lower
THD.
Correct
position
of
the
core
is
normally
just
above
the
metal
casing.
D. SYNTHESIZER 1|.F. TRACKING
Maintain connection of DVM but disconnect 10.7MHz tap at TP7.
Apply 98MHz (60dBu) to FM antenna input and tune to 98MHz.
Adjust C16 for OVDC +20mV reading on DVM.
Fine adjust L9 for minimum THD.
Repeat (3) and (4) until no further improvement can be made.
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E. FRONT-END LF.
1. Connect DVM between TP3 (level) and ground.
2. Turn R48A fully clockwise and R48 fully counterclockwise.
3. Apply 98MHz (12dBu) to antenna input.
4.
Carefully
adjust
FE5
to
obtain
minimum
reading
on
DVM.
There
should
only
be
one
minimum.
F. R.F.
1. Apply 98MHz (6dBu) to antenna input.
2. Check if THD is better than 3%. If not, proceed to (3).
3.
Adjust
FE1,
FE2,
and
FE3
by
squeezing
or
stretching
using
a
non-metallic
tool
until
THD
is
better
than 3%.
4. Check THD at 90OMHz and 106MHz with 7dBu input. If THD is more than 3% for both fre-
quencies, re-adjust until required THD is met.