NAD 4130 - Alignment Method; Necessary Instrumentation for Alignment; Important Notes Before Alignment; Tuning Voltage Oscillator Adjustment

ALIGNMENT METHOD
FM ALIGNMENTS
NECESSARY INSTRUMENTATION
FM GENERATOR (less than 0.05% THD)
STEREO GENERATOR (less than 0.05% THD, more than 50 dB separation at 1 kHz.
AUDIO GENERATOR (not necessary if FM generator has built in sweep; i.e. SOUND TECHNOLOGY ST 1000A and
— $T 1020A)
2 AC VTVM’s (or one with left/right channel switch)
THD ANALYZER (resolution better than 0.1%)
OSCILLOSCOPE (5mV or better sensitivity, X input capability)
FREQUENCY COUNTER | |
VOM or DMM (high impedance, must read in mV)
DIODE DETECTOR PROBE
COPPER / FERRITE INDUCTOR
IMPORTANT While all FM generator output levels hereafter are referred to the 300 ohm input, 75 ohm input can
be used, but be aware of possible equiprnent groundloops and divide the RF output levei by 2.
Before alignments commence set input selector to tuner and release tape, mono and dynsep defeat
switches (out)
ALIGNMENT OF FRONTEND should only be necessary after repair to frontend or crysta! oscillator
circuits (pin 2 and 3 on IC7)
A TUNING VOLTAGE (OSCILLATOR)
It is essential to check tuning voltage before aligning the rest of the frontend.
Connect DMM between shield and pin 6 on frontend.
2. Tune to 108 MHz and adjust L 707 if voltage is incorrect.
SPECIFICATION 20.5V +0.5V
3. Tune to 87.5 M#z and read voltage, repeat step 2 and 3 if incorrect.
SPECIFICATION 3V+0.5V
B. RF ADJUSTMENT (TRACKING)
1. Connect RF generator to antenna input and detectorprobe to pin 1,1C 2 (IF DETECTOR).
with ground to detectorshield. Adjust sensitivity of oscilloscope to maximum (5mV or better) and modulate
FM generator sweep + 300 kHz or more WITH modulating (sweep) signal connected to X-imput of
oscilloscope.
2.
Set
tuner
to
90
MHz,
enter
into
preset
1,
and
tune
generator
so
that
curve
appears
on
oscilloscope.
Turn
down
RF
input
level
so
that curve
covers
approximately
1/2
of
oscilloscope
display.
3.
Check
alignments
of
L
702
—
L
704
—
L705
by
inserting
copper/ferrite
inductor
close
to
them
while
watching
curve
on
oscilloscope.
Curve
should
decrease
in
height
with
either
ferrite
(same
as
increasing
inductance,
i.e,
more
core)
or
with
copper
(same
as
decreasing
inductance,
i.e.
extend
size
of
coil).
If
curve
increases
in
size
more
than
10%,
adjust
only
the
coil
which
reacts
incorrectly.
Adjust
coils
by
gently
extend
or
contract
the
aircoil
with
a
non-metallic
and
non-static
tool
(i.e.
plastic
knit-pin
or
a
wooden
stick).
Be
careful
not
to
deform
coil.
Set tuner to 105MHz, enter into preset 2, and tune generator so that curve appears on oscilloscope,
5.
Check
L
702
—
L
704
—
L
705
again
with
the
ferrite/copper
inductor.
Curve
should
not
increase
more
than
10%
on
any
of
the
coils.
6.
Repeat
step
2+ 3+
4+
5
if
curve
height
is
outside
of
telerances,
if
necessary
distribute
the
error
between
90
and
105 MHz.
Check
tuning
voltage again
if tolerances
not
possible
to achieve.
es IF ADJUSTMENT
1.
Set
tuner
to
approximately
98
MHz
(the
tuner
must
be
tuned
to
an
unoccupied
frequency)
enter
into
preset
3,
and
tune
FM
generator
to
display
a
curve
on the
oscilloscope.
2.
Adjust
L
709
(IFT
tuner
frontend)
to
maximum
and
symmetrical
curve
on
the
display,
using
as
little
input
signal as
possible.
—~5-—
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