Nad T761 Schematic

NAD

SERVICE MANUAL

T 761

SURROUND

SOUND RECEIVER

T 761

SURROUND

SOUND RECEIVER

2

SERVICE SAFETY PRECAUTIONS

1. Replacing the fuses
CAUTION: FOR CONTINUED PROTECTION AGAINST THE RISK OF FIRE REPLACE ONLY

WITH SAME TYPE OF FUSE.

Reference No Part Number Description

M752 *C 5120-0017-0 FU T4A 250V SEMKO/UDE HBC
M754 *C 5120-0018-0 FU T1A 250V SEMKO/UDE 5X20MM
M751 *AH 5120-0040-0 FU T6.3A 250V 5X20 UL
M754 *AH 5120-0052-0 FUSE T1.6A 250V 5X20MM

NOTE:

<*AH > : USA, CANADIAN MODEL ONLY.
<*C > : EUROPEAN MODEL ONLY.

2. Safety check out

(Only U.S.A. model)
Before returning the product to the customer, make leakage current or resistance measurements
to determine that exposed parts are acceptably insulated from the supply circuit.

Parts marked with the symbol are critical with regard to the risk of fire and electric shock.
Replace only with parts recommended by the manufacturer.

CONTENTS

DESCRIPTION PAGE

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

REAR PANEL / FRONT PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

DISASSEMBLY INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-8

BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

ADJUSTMENT POINTS DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

INSTRUMENT SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

ALIGNMENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12

IMPORTANT NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

PCB LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-25

SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26-44

IC BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45-52

ELECTRICAL PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53-75

EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

EXPLODED VIEW PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77-78

PACKING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79

3

SPECIFICATIONS

POWER AMPLIFIER AND PREAMPLIFIER SECTION

Rated distortion (THD 20Hz-20 kHz FL/C/FR) ≤ 0.08%

(THD 20Hz-20 kHz SL/SR) ≤ 0.3%
Input Sensitivity (ref. 8 ohms, 1 kHz) 180+/-30 mV
S/N Ratio (A-wtd, 1KHz, 1W, 8 ohm) ≥ -75 dB

(A-wtd, 1KHz, 80W, 8 ohm) FL/FR/C ≥ 92 dB

SL/SR ≥ -90 dB
Frequency Response (20 Hz - 20 kHz) 0 ± 0.8 dB
Channel Balance (1 dB to -40 dB, 1 kHz) ≤ 2 dB

(-41 dB to -50 dB, 1 kHz) ≤ 3 dB
Audio muting at 1kHz ≥ 53 dB
Headphone O/P in 0.1%, 600 ohm load, CD in 500mV, 1 kHz ≥ 10V
Subwoofer out, 500mV in (THD at 2V O/P, 100 Hz) ≥ 0.5%

(S/N at 2V O/P, 100 Hz) ≥ 80 dB
Crosstalk (2V input, 10W, 1 kHz) > -68 dB
Continuous average power output (L/R/C RL/RR 8ohms) 80 W

Controls

Bass (at 500mV in, 1W out, 100 Hz) ±9 dB
Treble (at 500mV in, 1W out, 10 kHz) ±9 dB

SURROUND SECTION
Channel separation

I/p mode : L, R : 1V in, 1 kHz, Ch R, L ≥ 45 dB

: o/p at unexpected, 1 kHz, Ch C ≥ 35 dB

I/p mode : L= -R : 1V in, 1 kHz, Ch R, L ≥ 28 dB

: o/p at unexpected, 1 kHz, Ch C ≥ 30 dB

I/p mode : L= R : 1V in, 1 kHz, Ch R, L ≥ 45 dB

: o/p at unexpected, 1 kHz, Ch SL, SR ≥ 30 dB

Frequency Response

I/p mode : L, R : 1V in, 1W, Ch R, L 40Hz 0 ± 1.5 dB

20kHz 0 ± 0.8 dB
I/p mode : L= R : 1V in, 1W, Ch C 300Hz 0 ± 0.8 dB

20kHz 0 ± 0.8 dB
I/p mode : L= -R : 1V in, 1W, Ch SL, SR 30Hz 0 ± 1.0 dB

6.5kHz -3 ± 1.0 dB
S/N Ratio ( 200mV in, 1, A-WTD w/ 1k termination)
I/p mode : L, R : 1 kHz, Ch L, R ≥ 65 dB
I/p mode : L=R : 1 kHz, Ch C ≥ 65 dB
I/p mode : L=-R : 1 kHz, Ch SL, SR ≥ 65 dB
THD (2.2V in, 1W, w/ 80 kHz LPF, 1 kHz) ≤ 0.2%

AC-3/DTS SECTION
Frequency Response

FL, FR, C, SL, SR: 200Hz 0 ± 0.8 dB

20kHz 0 ± 0.8 dB
Distortion 1W all channels 0.08%
S/N 1 W ( CCIR/ARM, 200 Hz NOTCH & 400 Hz HPF) ≥ 85 dB

4

AM TUNER SECTION

Input level is expressed as the reading in open-circuit
of 75-ohm source impedance signal generator
Usable sensitivity (999/1000kHz) ≤ 30 dBµ
S/N Ratio (5mV in) ≥ 38 dB
THD (5mV in) ≤ 3%
IF Rejection (450 kHz) ≥ 36 dB
Image Rejection (F+2xIF) ≥ 28 dB
Selectivity ≥ 17 dB
Output 130+/- 20mV
Loop sensitivity (20dB S/N)

999/1000 kHz ≤ 66 dB
603/600 kHz ≤ 66 dB
1404/1400 kHz ≤ 66 dB

Frequency response (100 - 2.3 kHz, 5mV) ± 6 dB

FM TUNER SECTION

*C *AH

Input level is expressed as the reading in open-circuit
of 75-ohm source impedance signal generator
Usable Sensitivity ( 98 MHz) ≤ 15 dBµ ≤ 15 dBµ
Signal / Noise Ratio Mono ≥ 72 dB ≥ 72 dB

(60 dBµ, IHF wtd) Stereo ≥ 66 dB ≥ 66 dB
Frequency Response (20 Hz - 15 kHz, 60 dBµ) 0 ± 1.5 dB 0 ± 1.5 dB
Channel Separation (60 dBµ) 100 Hz ≥ 30 dB ≥ 30dB

1 kHz ≥ 38 dB ≥ 38 dB
10 kHz ≥ 30 dB ≥ 30 dB

Alternate Channel Selectivity

(40 dBµ, ±400 kHz) ≥ 60 dB ≥ 45 dB
Capture Ratio (40 dBµ) ≤ 3 dB ≤ 3 dB
AM Suppression

(60 dBµ, 100% Mod.FM, 30% Mod.AM) ≥ 48 dB ≥ 48 dB
Image Rejection (119.4 MHz) ≥ 85 db ≥ 40 dB
I.F. Rejection ( 10.7 MHz) ≥ 78 dB ≥ 65 dB
Pilot Suppression (60 dBµ) ≥ 60 dB ≥ 60 dB
THD (60 dBµ, L=R 75 kHz for AH, 40 kHz Dev for C)

Mono ≤ 0.25% ≤ 0.25%
Stereo ≤ 0.35% ≤ 0.35%

Auto-Search Sensitivity On ≥ 24 dBµ ≥ 24 dBµ

Off ≤ 15 dBµ ≤ 15 dBµ

RDS decode Sensitivity ≤ 26 dBµ ≤ 26 dBµ

POWER RA

TING

EUROPEAN Model *C AC 230V~ 50Hz 2.0A
USA, CANADIAN Model *AH AC 120V~ 60Hz 4.2A

PHYSICAL

SPECIFICATIONS

Dimensions (Width x Height x Depth) 435 x 131 x 348mm
Net weight 14kg (31 lbs)
Shipping weight 16.7kg (37 lbs)

5

1. FM & AM ANTENNA

2. TAPE 1 & CD INPUTS

3. DISC INPUT

4. VIDEO 1 - VIDEO 4 (AUDIO & VIDEO)

5. 5.1 CHANNEL INPUT

6. DIGITAL AUDIO INPUTS / OUTPUTS

7. AUDIO PRE OUTS

8. COMPONENT VIDEO INPUT & OUTPUT

9. MONITOR OUT

10. SPEAKERS A: FRONT, CENTER & SURROUND
SPEAKERS

11. SPEAKERS B

12. SOFT CLIPPING

13. NAD-LINK INPUT / OUTPUT

14. 12V TRIGGER INPUT / OUTPUT

15. SWITCHED POWER OUTLETS

16. AC POWER CORD

17. COOLING FAN

1. POWER

2. STAND-BY

3. DISPLAY

4. AM/FM

5. FM MUTE / MODE

6. MEMORY

7. PRESET / TUNE

8. DOWN / UP AND

9. VFL DISPLAY

10. VOLUME & SETUP

11. HEADPHONE SOCKET & VIDEO 5 INPUT

12. SPEAKERS A& B

13. AUDIO & VIDEO INPUT SELECTORS
<DOWN/UP>

14. TAPE MONITOR

15. DIGITAL AUDIO SELECTOR

16. EXT. 5.1

17. SURROUND MODE

18. LEVELS

19. TONE CONTROLS & TONE DEFEAT

REAR PANEL / FRONT PANEL

REAR PANEL

FRONT PANEL

1617

13 1914 15 16 17 18

6

DISASSEMBLY INSTRUCTIONS

1. Remove machine screws M 4.0 x 6.0 ( 1 to 6 ) from the side panels.
Remove tapping screw 3.0 x 8.5 ( 7 )from the back panel.
Refer to Figure No.1.

Figure No.1

2. Pull both sides of the TOP COVER slightly outwards 8 and tilt approx. 35˚ and then remove
in the direction as indicated by the arrow 9 . Refer to Figure No.2.

Figure No.2.

7

6

5

1

3

2

4

9

8

8

87

WIRING DIAGRAM

J402A

RL-B

FR-B

J803A

J402B

J803B

COMPONENT VIDEO PCB

C834

J605B

J802B

J101B

DIGITAL IN PCB

NOTES :

SHOWN THE WAFERS

SHOWN THE SOLDER END OF HARNESS

SHOWN THE PIN 1 OF WIRE HARNESS

7706-1220-1004

7702-1060-2004

7010-1660-1

(J206C)

7712-1150-3004

7703-1090-2004

7703-1480-2004
7710-1200-3004

7711-1320-2004

7710-1100-3004

7708-1150-3004

7706-1100-2004

7012-5050-0 (J203C)

7703-1360-2004

7704-1200-2004

L

N

7703-1430-2004

7012-5030-0 (J101C)

7706-1220-1004

7706-1480-3004

7712-1400-2004

7012-5040-0 (J604C)

7706-1480-3004

POWER CORD

1681-0060-D

1681-0010-D

1681-0010-D

1681-0010-D

AC OUTLET PCB

J102B J701B

J901A

DIGITAL PCB

OUT

J503B

J801B

SPEAKER PCB

J7001

J401B

J709A

J710A

J901B

J708A

J703A

J708B

J704A

J706A J705A

J206B

J502B

J701A

J701B

MAIN PCB

J711A J707A

J703B

J704B

TUNER PCB

AUDIO PCB

J711B J707B

VIDEO PCB

J709B J710B

S-VIDEO PCB

J705B

J706B

J602A

J601A

J603A

MULTI CHANNEL PCB

SWITCH PCB

J208B

J206A

J207A

J204A

J203A

J201AJ202A

KEYBOARD

J207B

VOL PCB

J208A

POWER LED PCB

J201B

P751

P752

P753

P754

PSU PCB

J401A

VIDEO 5 PCB

J202B

J701A

J702A

J501B

SECONDARY PCB

PRIMARY PCB

J505B

J502A

J802B

J503A

J501A

J504A

J603B

FRONT AMP PCB

J604B

J802A

J801A

SURROUND AMP PCB

J204B

J702B

J504B

LOAD PCB

J203B

J101A

J601B

J604B

J102A

AC3 PCB

9 10

BLOCK DIAGRAM

COAXIAL x3

OPTICAL x2

4053

74LS157

M62446FP

COAXIAL Digital out

Com-Video

Trigger IN

POWER DOWN

Detect Pin.

For SPK off,

Mute ON, VFD off.

SPK. A and B

Trigger out

ADJUSTMENT POINTS DIAGRAM

1. TUNER

2. IDLE CURRENT - Front Amplifier & Surround Amplifier Board

RFOSC

VT

11

ALIGNMENT PROCEDURES

AMPLIFIER SECTION

Idle Current

Step Item Connection Adjustment Adjust for

1 Front Left Channel Voltmeter to P502 on Front Amp Board R574 2mV±0.2mV
2 Front Right Channel Voltmeter to P501 on Front Amp Board R573 2mV±0.2mV
3 Center Channel Voltmeter to P503 on Front Amp Board R599 2mV±0.2mV
4 Rear Left Channel Voltmeter to JP801 on Surround Amplifier Board R867 2mV±0.2mV

(PCB N0901C-AMP2)

5 Rear Right Channel Voltmeter to JP802 on Surround Amplifier Board R868 2mV±0.2mV

(PCB N091C-AMP2)

INSTRUMENT SETUP

1. FM MEASUREMENT

Fig. 1

Fig. 2

2. RDS MEASUREMENT

Fig. 3

3. AM MEASUREMENT

Fig. 4

FM

SIGNAL

GENERATOR

ANTENNA

TERMINAL

OUTPUT

TERMINAL

DISTORTION

ANALYZER

DISTORTION

ANALYZER

AC

VOLTMETER

OSCILLOSCOPE

AC

VOLTMETER

OR

OSCILLOSCOPE

AC

VOLTMETER

OR

OSCILLOSCOPE

OUTPUT

TERMINAL

OUTPUT

TERMINAL

L
R

ANTENNA

TERMINAL

ANTENNA

TERMINAL

ANTENNA
TERMINAL

AM LOOP
ANTENNA

(Accessory)

AM LOOP

ANTENNA

60cm

DIGITAL

MILLIVOLT

METER

VT-J914

FM

SIGNAL

GENERATOR

AM

SIGNAL

GENERATOR

FM

SIGNAL

GENERATOR

RDS

GENERATOR

FM

STEREO

GENERATOR

P-901

DC

MILLIVOLT

METER

UNIT

UNIT

UNIT

UNIT

12

FM/RDS SECTION

- FM mono: 1kHz, 75kHz devi., 60dB/µV

- FM stereo: 1kHz, 67.5kHz devi., 60dB/µV

Pilot signal 19kHz 7.5kHz devi.

OUTPUTS

- Connect the non-inductive type resistor of 8 ohms to the all speaker terminals unless otherwise noted.

Item

FM

IF/RF

Stereo

Distortion

Stereo

Separation

Muting

Level

Signal
output

Step

1

DC voltmeter L941

0±100mV

3

Distortion

analyzer

Distortion

analyzer

Oscilloscope

Oscilloscope

L942

R956

R941

Minimum

Minimum

2 AC voltmeter

IFT on the

front end

IFT on the

front end

Maximum

Maximum

separation

Connection

of instrument

Fig.1 –

–

Fig.2

Fig.2

Fig.1

Channel L
or R 1kHz

99.0MHz
1kHz 75kHz devi.
65dBf (60dB)

99.0MHz Ext.
mod. 65dBf
(60dB)

FM SG

output

Stereo mod­ulator output

Tuning

frequency

99.0MHz

99.0MHz

Channel L
or R 1kHz

99.0MHz Ext.
mod. 65dBf
(60dB)

99.0MHz Ext.
mod.65dBf(60dB)
RDS 2% MOD

99.0MHz 18dB

99.0MHz

99.0MHz

RDS

–

–

–

–

Fig.3

99.0MHz

Output

indicator

Adjustment

point

Adjust

for

Remarks

FM MUTE/MODE
switch: ON/AUTO
Repeat the steps
1 to 3 until no fur­ther adjustment is
necessary.

FM MUTE/MODE
switch: ON/AUTO
Don’t turn more
than +/-180˚

Repeat stereo
distortion and
stereo separation
alignment until
THD at minimum
and separation at
maximum.

Decode the RDS­Program Station.

AM SECTION

AM Modulation: 400Hz, 30%
For AH Version

Step

1–

2

3

530kHz

600kHz

990kHz

600kHz
400Hz 30% mod.
60dB/m

AM SG

output

Tuning

frequency

Output

indicator

Adjustment

point

600kHz
400Hz 30% mod.
60dB/m

AC

voltmeter

AC

voltmeter

Digital

DC

voltmeter

L972

OSC coil

on RF

block L971

RF coil

on RF

block L971

Adjust

for

1.35±0.2V

Maximum

Maximum

Step

1–

2

3

522kHz

or

531kHz
603kHz

999kHz

600kHz
400Hz 30% mod.
60dB/m

AM SG

output

Tuning

frequency

Output

indicator

Adjustment

point

600kHz
400Hz 30% mod.
60dB/m

AC

voltmeter

AC

voltmeter

Digital

DC

voltmeter

L972

OSC coil

on RF

block L971

RF coil

on RF

block L971

Adjust

for

1.3±0.2V (522kHz)

1.35±0.2V (531kHz)

Maximum

Maximum

For C Version

13

IMPORTANT NOTES

1. Show the software version

Press “TUNE UP” and “TAPE MONITOR”.

2. Toggle between PAL and NTSC

Press “MEMORY” and “SPEAKER A”.

3. Light up all the icon on the VFL.

Press “FM/MUTE” and “SPEAKER B”.

4. Toggle between 9K and 10K

Press “FM/MUTE” and “Digital Audio Selector”.

5. Clear all tuner presets

Change the setting of 9KHz / 10KHz Step.

14

PCB LAYOUT

SPEAKER BOARD

PRIMARY BOARD

LED BOARD

SECONDARY BOARD

AC OUTLET BOARD

15

DIGITAL IN BOARD

S-VIDEO BOARD

DIGITAL OUT BOARD

16

PSU BOARD

COMPONENT VIDEO BOARD

17

LOAD BOARD

VOLUME BOARD

(Top View) (Bottom View)

SURROUND AMP BOARD

VIDEO 5 BOARD

18

AC3 BOARD - COMPONENT SIDE

19

AC3 BOARD - SOLDER SIDE

20

FRONT AMP BOARD

2221

KEY BOARD - COMPONENT SIDE

KEY BOARD - SOLDER SIDE

23 24

MAIN BOARD VIDEO BOARDMULTI-CHANNEL BOARD

AUDIO BOARD

POWER SWITCH BOARD

26

T

O MAIN BOARD

J707A

T

O MAIN BOARD

J711A

SCHEMATIC DIAGRAM

AUDIO

NOTE: 1. RESISTORS, ARE CARBON FILM 5% 1/8W UNLESS OTHERWISE SPECIFIED.

2. CERAMIC CAPACITORS, ARE 50V 10%. UNLESS OTHERWISE SPECIFIED.

25

TUNER BOARD