NAD M-3 Schematic
SERVICE MANUAL
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MODEL: M3SERVICE MANUAL
© NAD 2006
NAD ELECTRONICS INTERNATIONAL
TORONTO
Integrated Amplifier
M3 C/AH
SERVICE MANUAL
M3 C/AH
Integrated Amplifier
M3 C/AH
Integrated Amplifier
BLOCK DIAGRAMS
1. POWER DISTRIBUTE DIAGRAM
L CHANNEL
TRANSFORMER
MAIN
±20V RECTIFY
B605
ON PSU
±72V RECTIFY
B606
ON PSU
HIGH CURRENT
POWER SUPPLY
RECTIFY
B603 B604
ON PSU
L CHANNEL
INPUT RELAYS
ON PREAMP
L CHANNEL
OUTPUT RELAYS
ONLAMP
±20V REGULATOR
B606
ON PSU
±72V REGULATOR
B606
ON PSU
ISC CIRCUIT
D602 D603
ON PSU
BALANCE AMP
ON BAL
PRE AMP
ON PRE AMP
L CHANNEL
AMPLIFIER
ON L AMP
AC INLET EMI FILTER
STANDBY RELAY
POWERSWITCH
FUSE F902
AH: 5A 250V
C: 3.15A 350V
FUSE F901
100mA 250V
FUSE F903
AH: 5A 250V
C: 3.15A 350V
R CHANNEL
MAIN
TRANSFORMER
R-CORE
STANDBY
TRANSFORMER
HIGH CURRENT
POWER SUPPLY
RECTIFY
B603 B604
ON PSU
±72V RECTIFY
B606
ON PSU
±20V RECTIFY
B605
ON PSU
5V REGULATOR
B901 IC1
12V RECTIFY
B902
ISC CIRCUIT
D602 D603
ON PSU
±72V REGULATOR
B606
ON PSU
±20V REGULATOR
B606
ON PSU
L CHANNEL
INPUT RELAYS
ON PREAMP
LOGIC CIRCUIT
ON PREAMP
MCU
LOGIC CIRCUIT
ON FPP
12V TRIGGER
ON BAL
STANDBY
RELAY
ON PSU
L CHANNEL
AMPLIFIER
ONLAMP
BALANCE AMP
ON BAL
PRE AMP
ON PRE AMP
3-9
L CHANNEL
OUTPUT RELAYS
ONLAMP
2. PREAMP SIGNAL PATH
LEFT CHANNEL
DISC
CD
TUNER
INPUT4
INPUT5
INPUT6
BALANCE
DISC
CD
TUNER
INPUT4
INPUT5
INPUT6
BALANCE
BALANCE AMP
BALANCE AMP
INPUT SELECTOR
INPUT SELECTOR
STEREO/MONO
SWITCH
0/6.5dB SELECTABLE GAIN
AMP STAGE
0/6.5dB SELECTABLE GAIN
AMP STAGE
54dB ATTENUATOR
2dB/STEP
54dB ATTENUATOR
2dB/STEP
5dB TONE CONTROL
1dB/STEP
5dB TONE CONTROL
1dB/STEP
RIGHT CHANNEL
2,2.5,3,3.5dB SELECTABLE GAIN
AMP STAGE
2,2.5,3,3.5dB SELECTABLE GAIN
AMP STAGE
30dB ATTENUATOR
10dB/STEP
30dB ATTENUATOR
10dB/STEP
BIAMP HIGH PASS FILTER
BY PASS, 40, 60, 80, 100Hz
BIAMP HIGH PASS FILTER
BY PASS, 40, 60, 80, 100Hz
PRE OUT1
PRE OUT2
PRE OUT1
PRE OUT2
3-10
3. SYSTEM CONTROL PATH
P0.0
P0.1
P0.2
P0.3
P0.4
P0.5
P0.6
P0.7
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0
P3.1
P3.2
MCU
AT89C51
P3.3
P3.4
P3.5
P3.6
P3.7
P4.0
P4.1
P4.2
P4.3
P4.4
P4.5
P4.6
P4.7
P5.0
P5.1
P5.2
P5.3
P5.4
P5.5
P5.6
P5.7
VFD
KEYS
U83 MAX3221 (FPP)
Q85 Q86 (FPP) IR IN/OUT SOCKET ( REAR PANEL)
Q89 inverter(FPP) Protect Circuit (High when Protect)
Q91 (PSU) OP91 OPTOISO (PSU) RL91 standby relay (PSU)
U84 U85 7400 (FPP) D81 Tri-color LED (FPP)
U108 U113 U208 U213
CD4094 (PRE)
U110 U210 (PRE)
CD4094
U105 (PRE) TC9274
U205 (PRE) TC9274
U109 U209 (PRE)
TC9274
U109 U209 (PRE)
TC9274
RL301 RL302 RL401 RL402
OUTPUT RELAYS (LAMP/RAMP)
ENCODE
EEPROM
RJ45 RS232 SOCKET (REAR PANEL)
RL101 ... RL112, RL201 ... RL212
For Input Select and Biamp Filter Switch
Q130 Q131 Q230 Q231 for Mute
U104 U107 U204 U207 (PRE) MAX4621
30dB Attenuator, Q101...Q103, Q201...Q203,
6.5 Gain/ 0.5 Gain Switch
3-11
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