NAD T-741 Service manual

NAD

T 741

SURROUND

SOUND RECEIVER

T 741

SURROUND

SOUND RECEIVER

SERVICE MANUAL

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

M271 *C 5120-0024-0 3.15A TIME-LAG 5x20 VDE-SEMKO

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-11

INSTRUMENT SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

ALIGNMENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-13

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

PCB LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-24

SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25-42

IC BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43-51

ELECTRICAL PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52-71

EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

EXPLODED VIEW PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73-74

PACKING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75

3

SPECIFICATIONS

POWER AMPLIFIER AND PREAMPLIFIER SECTION (all channels stated 8 ohms)

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) ≥ -78 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 8 ohms) 50 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 ± 1.5 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%

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%

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

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

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

1 kHz ≥ 40 dB
10 kHz ≥ 30 dB

Alternate Channel Selectivity

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

(60 dBµ, 100% Mod.FM, 30% Mod.AM) ≥ 48 dB
Image Rejection (119.4 MHz) ≥ 68 db
I.F. Rejection ( 10.7 MHz) ≥ 78 dB
Pilot Suppression (60 dBµ) ≥ 60 dB
THD (60 dBµ, L=R 75 kHz for AH, 40 kHz Dev for C)

Mono ≤ 0.25%
Stereo ≤ 0.35%

Auto-Search Sensitivity On ≥ 24 dBµ

Off ≤ 15 dBµ

RDS decode Sensitivity ≤ 26 dBµ

POWER RA

TING

EUROPEAN Model *C AC 230V~ 50Hz 1.2A
USA, CANADIAN Model *AH AC 120V~ 60Hz 2.5A

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. 5.1 CHANNEL INPUT

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

5. NAD-LINK INPUT / OUTPUT

6. DIGITAL AUDIO INPUTS / OUTPUTS

7. 12V TRIGGER INPUT

8. AUDIO PRE OUTS

9. MONITOR OUT

10. SOFT CLIPPING

11. SPEAKERS: FRONT, CENTER & SURROUND
SPEAKERS

12. AC POWER CORD

1. POWER

2. STAND-BY

3. AM/FM

4. DISPLAY

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. VIDEO 1 ~ VIDEO 5 INPUT

13. CD

14. TAPE MONITOR

15. EXT. 5.1

16. SURROUND MODE

17. SET UP

18. TONE CONTROLS

REAR PANEL / FRONT PANEL

REAR PANEL

FRONT PANEL

891011 12

1

23 4 5 6 7

12 345678 9

10

11 12 13 14 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

POWER CORD

L

N

P266

P265
P261

P260

P262

T201A

PRIMARY PCB

SECONDARY PCB

J701A J202B

PSU PCB

P264

T202A

J206A

J201B

J101B

P261

DIGITAL PCB

JP203

J206B

JP205

JP206

JP204

SURROUND

AMPLIFIER PCB

JP210
JP211

SPEAKER PCB

P262 P260

C221

JP209

JP207

C230

M704B

J602B

JP210

J702B

S-VIDEO PCB

+35V

-35V

J716B

J715B

J716A

J715A

M707A

M708A

GND

MAIN PCB

J702A

M705A

JP207B

J714A

J709B

J710B

J401B

VIDEO PCB

J701B

J706B

J604A

J705B

J206B

J703A

J704A

JP212B

J714B

AUDIO PCB

MULTI CHANNEL PCB

J602A

J706B

J601A

J705B

J710B J709B

J703B

TUNER PCB

J704B

NOTES :

SHOWN THE WAFERS

J101A

J604B

POWER SWITCH PCB

P702

AC3 PCB

J203B

P701

J601B

J401A

VIDEO 5 PCB

POWER LED PCB

J208A

J208B

J203A

J202A J201A

KEYBOARD

J207A

J206A

SHOWN THE SOLDER END OF HARNESS

SHOWN THE PIN 1 OF WIRE HARNESS

VOL PCB

J207B

9 10

BLOCK DIAGRAM

ADJUSTMENT POINTS DIAGRAM

1. TUNER

2. IDLE CURRENT - Front Amplifier & Surround Amplifier Board

FL

FR

CENTERSLSR

SUB

FL

FR

OUT2

CENTERSLSR

OUT3

M62446FP

OUT1

SUB

OUT4

TUNER

R

L

TUNER

SPK. A and B

Trigger out

POWER DOWN

Detect Pin.

For SPK off,

Mute ON, VFD off.

VT

OSC RF

COAXIAL x2

74LS157

74HC153

OPTICAL x1

4053

TEMPERATURE

PROTECTION

Video

Selector

CD4051

S-Video

Selector

CD4052

Video Pin

1 IN 13

2 IN 12

3 IN 15

4 IN 14

5 IN 1

3 OUT 3

4 OUT 3

S-Video Pin

CY

1 IN 11 4

2 IN 12 1

3 IN 15 2

3 OUT 13 3

11

12

ALIGNMENT PROCEDURES

AMPLIFIER SECTION

Idle Current

Step Item Connection Adjustment Adjust for

1 Front Left Channel Voltmeter to M714 on Main Board VR7703 1mV±0.2mV

2 Front Right Channel Voltmeter to M713 on Main Board VR7702 1mV±0.2mV

3 Center Channel Voltmeter to M712 on Main Board VR7701 1mV±0.2mV

4 Rear Left Channel Voltmeter to TP202 on Surround Amplifier Board VR202 1mV±0.2mV

(PCB N0A00C-AMP2)

5 Rear Right Channel Voltmeter to TP201 on Surround Amplifier Board VR201 1mV±0.2mV

(PCB N0A00C-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

VOLT METER

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-J954

FM

SIGNAL

GENERATOR

AM

SIGNAL

GENERATOR

FM

SIGNAL

GENERATOR

RDS

GENERATOR

FM

STEREO

GENERATOR

P-901

DC

MILLIVOLT

METER

UNIT

UNIT

UNIT

UNIT

13

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 mod-

ulator 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

IMPORTANT NOTES

1. Show the software ver­sion

Press “FM/AM” and “EXT

5.1”.

2. Light up all the icon on
the VFL.

Press “FM/AM” and “TONE
CONTROL”.

3. Toggle between 9K and
10K

Press “FM/AM” and “CD”.

4. Clear all tuner presets

Press “TAPE(MON)” and
“VIDEO 1”.

14

PCB LAYOUT

S-VIDEO BOARD

VIDEO-5 BOARD

VOLUME BOARD

15

VIDEO BOARD

TUNER BOARD

16

SURROUND AMPLIFIER BOARD PRIMARY BOARD

SECONDARY BOARD

17

AUDIO BOARD

PSU BOARD

18

MULTI-CHANNEL BOARD - COMPONENT SIDE

19

MULTI-CHANNEL BOARD - SOLDER SIDE

20

MAIN BOARD

2221

AC3 BOARD - COMPONENT SIDE AC3 BOARD - SOLDER SIDE

23 24

KEY BOARD

DIGITAL BOARD

SPEAKER BOARD

LED BOARD

POWER SWITCH BOARD