NAD 712 - AM Section Alignment; Amplifier Adjustment Procedures; Output Offset Voltage Adjustment; Idle Current Adjustment

AM SECTION
For version conversion, press Tune UP while pressing Mode switch to toggle the AM steps between 9 kHz
and 10 kHz.
AF MODULATION: 400 Hz, 30%
FOR AH VERSION, STORE FREQUENCIES 600, 1000, 1400 kHz.
FOR C & B VERSIONS, STORE FREQUENCIES 603, 999, 1404 kHz.
Connect 22 pF ceramic capacitor between signal generator and antenna terminal.
OSCILLATION TUNING VOLTAGE
Connect DVM between TP701 & GROUND.
Tune to 603/600 kHz.
Adjust L705 for 1.75 + 0.05 V.
1.F.
Apply 999/1000 kHz, 35dBu to antenna input.
Tune to 999/1000 kHz.
Adjust L708 for maximum output.
R.F.
Apply 603/600 kHz, 45dBu.
Tune to 603/ 600 kHz.
Adjust L704 for maximum output.
Apply 1404/1400 kHz, 45dBu.
Tune to 1404/ 1400 kHz.
Adjust C721 for maximum output.
Repeat until no further improvement.
AMPLIFIER ADJUSTMENT
IMPORTANT
seve
impedance
switch
should
be
in
the
8
ohms
position
while
adjusting
the
amplifier.
eset
switch after
adjustment
procedure
is
completed.
1) Output Offset Voltage (No load, no input Signal)
Connect DC voltmeter across L channel speaker terminals.
Adjust R411 for 0 + 30 mV reading.
Connect DC voltmeter across R channel speaker terminals.
Adjust R412 for 0 + 30 mV reading.
2) Idle Current
Remove solder link in between TP 401 and TP403, or cut LK53.
Connect DC millivoltmeter at TP401 and TP403 (i.e. across R455, 1-ohm resistor).
Adjust R443 for 25-35mV reading on voltmeter.
Remove solder link in between TP 402 and TP404, or cut LK322.
Connect DC millivoltmeter at TP402 and TP404 (i.e. across R456, 1-ohm resistor).
Adjust R444 for 25-35 mV reading on voltmeter.
3) Final Adjustment
Leave power on for at least 5 minutes.
Repeat step 1
Repeat step 2
Replace
solder
link
between
T401
and
T403
for
left
channel,
and
TP402
and
TP404
for
right
channel,
or
reconnect
LK53
and
LK322.
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