Nad T-744 Service Manual
DRAFT DATE: 08 MAY 2007
NAD
SERVICE MANUAL
T 744
A/V Receiver
T 744
A/V Receiver
SAFETY INFORMATION
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 Designator Database Part Number Description
F751*AH
F752*AH
F751*C,CT
F752*C,CT
FH751-FH752
NOTE: <*AH > : USA, CANADIAN MODEL ONLY.
<*C,*CT > : 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 supply circuit.
20-001-0075-90 FUSE TIME-LAG 7A 250V 5 X 20mm
SIC UL/CSA (RoHS)
20-001-0076-90 FUSE 1.6A 250V TIME LAG LBC 5x20mm
TSD UL/CSA/VDE/SEMKO (RoHs)
20-001-0071-90 FUSE TIME-LAG 4A/250V 5 X 20mm
VDE/UL TSD (RoHS)
20-001-0069-90 FUSE 800mA 250V TIME LAG LBC
5x20mm TSD UL/CSA/VDE/SEMKO (RoHS)
20-002-0030-90 FUSE CLIP 0.05mm WL-210A
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............................................................................................................................ 4 - 5
REAR PANEL / FRONT PANEL VIEW .................................................................................................. 6
DISASSEMBL Y INSTRUCTIONS.......................................................................................................... 7
WIRING DIAGRAM & P AR TS LIST................................................................................................ 8 - 10
BLOCK DIAGRAM................................................................................................................................11
SPECIAL FUNCTION .......................................................................................................................... 12
DETAILS & WAVEFORMS ON SYSTEM & TEST & DEBUGGING .................................................... 12
ADJUSTMENT POINTS DIAGRAM / AMPLIFIER ADJUSTMENT ...................................................... 13
PCB LAYOUT............................................................................................................................... 14 - 25
SCHEMA TIC DIAGRAM ............................................................................................................... 26 - 42
IC BLOCK DIAGRAM ................................................................................................................... 43 - 49
EXPLODED VIEW............................................................................................................................... 50
EXPLODED VIEW PAR TS LIST................................................................................................... 51 - 53
ELECTRICAL PARTS LIST ........................................................................................................... 54- 66
PACKING DIAGRAM.......................................................................................................................... 67
3
SPECIFICATIONS
POWER AMPLIFIER SECTION
Rated distortion (Rated power level into 8 ohms, THD 20 Hz-20 kHz FL/C/FR) ≤ 0.1 %
(Rated power level into 8 ohms, THD 20 Hz-20 kHz SL/SR/BS) ≤ 0.1 %
Input Sensitivity (ref. 8 ohms, 1 kHz) 260
S/N Ratio (A-wtd, 1kHz, 1 W, 8 ohm, SL/SR/BL)
Frequency Response (20 Hz - 20 kHz) 0
Channel Balance (1 dB to -40 dB, 1 kHz) ≤ 2 dB
(-41 dB to -50 dB, 1 kHz) ≤ 3 dB
Audio muting at 1 kHz
Subwoofer out, 500 mV in (THD at 2 V O/P, 100 Hz) ≤ 0.5 %
Crosstalk (500 mV input, 10 W, 1 kHz)
±±
± 20mV
±±
≥≥
≥ - 75 dB
≥≥
±±
± 1.0 dB
±±
≥≥
≥ 55 dB
≥≥
≥≥
≥ -57 dB
≥≥
Controls
Bass (at 500 mV in, 1 W out, 100 Hz)
Treble (at 500 mV in, 1 W out, 10 kHz)
±±
± 10 dB
±±
±±
± 10 dB
±±
DOLBY DIGITAL SECTION
Channel Difference(FL ref. Track 30)
Frequency Resporse at Dolby config.2 SL Track 46 200 - 20 kHz
SR Track 47 200 - 20 kHz
C Track 44 200 - 20 kHz
Harmonic Distortion (1 W, Audio LPF, Dolby Congfig 1) FL Track 65 997 Hz ≤ 0.08 %
FR Track 67 997 Hz ≤ 0.08 %
SL Track 68 997 Hz ≤ 0.08 %
SR Track 69 997 Hz ≤ 0.08 %
C Track 66 997 Hz ≤ 0.08 %
S/N Ratio (TRACK 30 for O/P 1 W , FAUSE) CCIR / ARM
Audio LPF
A-WTD
Channel Separation (1 W, A-WTD FILTER) Track 65 997 Hz
±±
± 1.2 dB
±±
±±
± 0.8 dB
±±
±±
± 0.8 dB
±±
±±
± 0.8 dB
±±
≥≥
≥ 65 dB
≥≥
≥≥
≥ 70 dB
≥≥
≥≥
≥ 70 dB
≥≥
≥≥
≥ 60 dB
≥≥
±±
± 2 dB
±±
±±
± 2 dB
±±
DOLBY PRO LOGIC II SECTION
Frequency Resporse
I/P mode : L, R : 1 V in, 1 W, Ch L/R 40 Hz 0
20 kHz 0
I/P mode : L=R : 1 V in, 1 W , Ch /L/R 40 Hz 0
Ch C 20 kHz 0
I/P mode : L=-R : 1 V in, 1 W, Ch SL/SR 40 Hz 0
20 kHz 0
S/N Ratio (200 mV in, 1 W, A-WTD w/ 1 k termination)
I/P mode : L, R : 1 kHz, Ch L/R
I/P mode : L=R : 1 kHz, Ch C
I/P mode : L=-R : 1 kHz, Ch SL/SR
THD (2.2 V in, 1 W, w/ 80 kHz LPF, 1 kHz) ≤ 0.2 %
4
±±
± 2.0 dB
±±
±±
± 2.0 dB
±±
±±
± 2.0 dB
±±
±±
± 2.0 dB
±±
±±
± 2.0 dB
±±
±±
± 2.0 dB
±±
≥≥
≥ 65 dB
≥≥
≥≥
≥ 65 dB
≥≥
≥≥
≥ 65 dB
≥≥
DTS SECTION
Output Level (Vol 0 dB) : FL/FR/C/SL/SR Track 6 1 kHz 2.5
Channel Difference (FL ref) : FL/FR/C/SL/SR Track 6 1 kHz
Harmonic Distortion (Audio Filter) : FL/FR/C/SL/SR Track 10-14 1 kHz
Frequency Response (20 Hz to 20 kHz) Track 26-30 +2/-1.5
Subwoofer Output Level 1 kHz ref at pre-out (FL) Play Track 10, charge to 15 12.5
±±
± 0.2 W
±±
±±
± 1.0 dB
±±
≤≤
≤ 0.08 %
≤≤
±±
± 2 dB
±±
AM TUNER SECTION
Input level is expressed as the reading in open circuit
of 75-ohm source impedance signal generator
Usable sensitivity (999/1000 kHz)
S/N Ratio (5 mV in)
THD (5 mV in)
IF Rejection (450 kHz)
Image Rejection (F+2xIF)
Selectivity
Output 170
Loop sensitivity (20 dB S/N)
999/1000 kHz
603/600 kHz
1404/1400 kHz
Frequency Response (100 - 2.3 kHz, 5 mV)
≤≤
≤ 30 dB
≤≤
≥≥
≥ 38 dB
≥≥
≤≤
≤ 3 %
≤≤
≥≥
≥ 36 dB
≥≥
≥≥
≥ 28 dB
≥≥
≥≥
≥ 17 dB
≥≥
±±
± 20 mV
±±
≤≤
≤ 66 dB
≤≤
≤≤
≤ 66 dB
≤≤
≤≤
≤ 66 dB
≤≤
±±
± 6 dB
±±
µµ
µV
µµ
FM TUNER SECTION *C,*CT *AH,*AHT
Input level is expressed as the reading in open circuit
of 75-ohm source impedance signal generator
Usable sensitivity (98 MHz)
S/N Ratio (60 dB, IHF wtd) Mono
Stereo
Frequency Response (20 Hz - 15 kHz, 60 dB
Channel Separation (60 dB
Alternate Channel Selectivity (40 dB
Capture Ratio (40 dB
AM Suppression (60 dBµ, 100% Mod. FM, 30% Mod. AM)
Image Rejection (119.4 MHz)
I.F. Rejection (10.7 MHz)
Pilot Suppression (98 MHz)
THD (60 dB
Auto-Search Sensitivity On
RDS decode Sensitivity
µµ
µ, L=R 75 kHz for AH, 40 kHz Dev for C) Mono
µµ
µµ
µ) 100 Hz
µµ
µµ
±±
µ,
± 400 kHz)
µµ
±±
µµ
µ)
µµ
µµ
µ) 0
µµ
1 k
10 kHz
Stereo
Off
≤≤
≤ 15 dB
≤≤
≥≥
≥ 63 dB
≥≥
≥≥
≥ 63 dB
≥≥
≥≥
≥ 30 dB
≥≥
≥≥
≥ 38 dB
≥≥
≥≥
≥ 30 dB
≥≥
≥≥
≥ 60 dB
≥≥
≤≤
≤ 3 dB
≤≤
≥≥
≥ 48 dB
≥≥
−−
−
−−
≥≥
≥ 78 dB
≥≥
≥≥
≥ 60 dB
≥≥
≤≤
≤ 0.25 %
≤≤
≤≤
≤ 0.35 %
≤≤
≥≥
≥ 24 dB
≥≥
≤≤
≤ 15 dB
≤≤
≤≤
≤ 26 dB
≤≤
µµ
µ
µµ
±±
± 1.5 dB 0
±±
µµ
µ
µµ
µµ
µ
µµ
µµ
µ
µµ
≤≤
≤ 15 dB
≤≤
≥≥
≥ 63 dB
≥≥
≥≥
≥ 63 dB
≥≥
±±
± 1.5 dB
±±
≥≥
≥ 30 dB
≥≥
≥≥
≥ 38 dB
≥≥
≥≥
≥ 30 dB
≥≥
≥≥
≥ 45 dB
≥≥
≤≤
≤ 3 dB
≤≤
≥≥
≥ 48 dB
≥≥
≥≥
≥ 65 dB
≥≥
−−
−
−−
≥≥
≥ 60 dB
≥≥
≤≤
≤ 0.25 %
≤≤
≤≤
≤ 0.35 %
≤≤
≥≥
≥ 24 dB
≥≥
≤≤
≤ 15 dB
≤≤
−−
−
−−
µµ
µv
µµ
µµ
µ
µµ
µµ
µ
µµ
PHYSICAL SPECIFICATIONS
Dimensions (Width x Height x Depth) 435 x 150 x 390 mm
Net Weight 13.3 Kg (29.30 lbs)
Shipping Weight 16.9 Kg (37.20 lbs)
5
REAR PANEL / FRONT PANEL VIEW
REAR PANEL
1. FM & AM ANTENNA
2. MONITOR OUT
3. CD INPUT
4. DIGIT AL AUDIO INPUT &
DIGITAL AUDIO OUTPUT
5. SOFT CLIPPING ON/OFF
6. IR INPUT & OUTPUT
7. +12V TRIGGER INPUT & OUTPUT
8. COMPONENT VIDEO IN &
COMPONENT VIDEO OUT
FRONT PANEL
9. AC POWER CORD
10. POWER SWITCH
1 1. SWITCHED AC OUTLETS
12. SPEAKERS A & B
13. DVD, SAT, VCR, VIDEO 4 & VIDEO 5
14. MAIN IN / AUDIO PRE-OUTS /
SUBWOOFER OUT
15. T APE INPUT & OUTPUT
16. DISC INPUT
17. 5.1 CH. INPUTS
1. STANDBY SWITCH
2. STANDBY LED
3. AM / FM
4. DISPLAY
5. MEMORY
6. FM MUTE / MODE
7. PRESET DOWN / UP
8. SEARCH DOWN / UP
9. VFL DISPLAY
10. VOLUME (SETUP)
1 1. SOURCE DOWN / UP
12. SURROUND MODE
6
13. LEVELS
14. TONE DEFEA T
15. TONE CONTROLS
16. SPEAKERS A & B
17. VIDEO 6 INPUT
18. PHONES
DISASSEMBLY INSTRUCTIONS
1. Remove machine screws M4.0 x 8.0 (1 to 6) from the side panels.
Remove tapping screw 3.0 x 8.0 (7 to 10) from the back panel.
Refer to Figure No. 1.
Figure No. 1
2. Pull both sides of the TOP COVER slightly outwards 11 and tilt approx. 35 ° and then remove
in the direction as indicated by the arrow 12. Refer to Figure No. 2.
Figure No. 2
7
WIRING DIAGRAM
FROM TRANSFORMER
LED BOARD
J204A
15
10
5
P4402
P4401
J3103B J709B
VIDEO 6 INPUT
J781A
J786A
J782A
J783A
J784A
21
J751B
J753_N J753_L
J753A
18
4
22
J754B
J758_N
J759_L
2627
J350A
24
FOR T2743 120V VER.FOR T2743 120V VER.
23
J414B
J786B
J506B
J505B
J801B
20 19
J1009A
J705A
J1010A
J414A
7
J710B
J602B
17 16
J601B
J3103B
J603B
J711B
J611A
J707B
J705B
J704B
J612A
21
J504A
J504B
J781B
J506A
J503B
J709A
J501A
J715A
J611B
J505A
J502B
J710A
J717A
J719A
J501B
J612A
J502A
J503A
14
J701
3
J782B
J713A
J714A
J350B
J801A
J506A
J704A
J707A
J711A
J606B
J720A
2525
31 33
9
J204B
J753B
J713B J714B
J715B
13
J203A
J201
J604B
J203B
DSP BOARD
J1010B
J601A
J717B
J719B
J602A
32
J603A
J606B
28
12
J1009B
30
6
8
29
TUNER
J604A
11
8
WIRING DIAGRAM PARTS LIST
Item Database Part Number Description Remark
1 17-012-2959-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1007 AMP1
2 17-012-2969-90 CABLE ASSY 5 WAYS P3.96 AWG18 UL1007 AMP1
3 17-012-2976-90 CABLE ASSY 12 WAYS AWG=26 2.5P UL2877 AMP1
4 17-012-2959-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1007 AMP2
5 17-012-2966-90 CABLE ASSY 4 WAYS AWG26 2.5P UL1533 AUDIO
6 17-012-2957-90 CABLE ASSY 2 WAYS AWG=26 2.5P UL1533 DIGIT BD-
7 17-012-2961-90 CABLE ASSY 3 WAYS AWG=26 X2C P=2.5 DIGITAL BD-
8 17-012-2967-90 CABLE ASSY 4 WAYS AWG=26 2.5P DIGITAL BD-
9 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK KEYBOARD-
10 17-012-3404-90 CABLE ASSY 5 WAYS AWG26 2.5P UL1007 LED BD-
11 17-012-2963-90 CABLE ASSY 3 WAYS AWG=26 2.5P L=110mm MAIN BD-
12 17-012-2964-90 CABLE ASSY 3 WAYS AWG26X2C UL2547 MAIN BD-
13 17-012-2974-90 CABLE ASSY 8 WAYS AWG=26X3C L=480mm MAIN BD-
14 17-012-2977-90 CABLE ASSY 12 WAYS AWG26 2.5P UL2468 MAIN BD-
15 17-012-2978-90 CABLE ASSY 14 WAYS AWG=26 2.5P UL1007 MAIN BD-
16 17-012-2962-90 CABLE ASSY 3 WAYS AWG=26 2.5P UL2854 PO BD-
17 17-012-2972-90 CABEL ASSY 6 WAYS AWG=26 2.5P PO BD-
18 17-012-2965-90 CABLE ASSY 4 WAYS AWG26 2.5P UL2468 PS BD-
19 17-012-2958-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1007 SPK
20 17-012-2960-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1015 SPK BD-
21 17-012-2968-90 CABLE ASSY 5 WAYS AWG=18 3.96P UL1007 SPK BD-
22 17-012-2970-90 CABLE ASSY 5 WAYS AWG18 UL1007 SPK BD-
23 17-012-2973-90 CABLE ASSY 8 WAYS AWG=26 2.5P UL1007 SV BD-
24 17-012-2975-90 CABLE ASSY 8 WAYS AWG=26 2.5P UL1007 TR BD-
25 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK V6 BD-
26 17-012-2948-90 CABLE ASSY 1 WAY AWG=16 UL1672 J759
27 17-012-2874-90 CABLE ASSY 1 WAY AWG=16 UL1672 J758
28 17-010-0032-90 FFC CABLE 30 PINS P1.25 L=70mm J601A
L=180mm BD-J504A
L=200mm BD-J501A
L=120mm BD-J503A
L=180mm BD-J781B
L=450MM (ROHS) BD-J3103A
L=540mm (ROHS) J1009A
UL2854 L=110mm C33110 (RoHS) J705A
UL2877 L=500mm (RoHS) J1010A
L=100mm W/ RING TERMINAL (RoHS) J201
L=160mm (RoHS) J204A
J606B
L=210mm (UL LABEL) (RoHS) J715A
(RoHS) J709A
L=230mm (UL LABEL) (RoHS) J502A
L=440mm (UL LABEL) (RoHS) J782B
L=420mm (RoHS) J611A
UL1533X1C L=350mm (RoHS) J612A
L=400mm (ROHS) J753A
L=120mm BD-J801B
L=320mm J505B
L=350mm J786B
L=300mm (V/B/Y) (UL LABEL) (RoHS) J506B
L=380mm (RoHS) J414A
L=540mm (UL LABEL) (RoHS) J350A
L=100mm W/ RING TERMINAL (RoHS) P4401,P4402
BROWN L=100mm
BLUE L=100mm
W/SHIELD
9
Item Database Part Number Description Remark
29 17-010-0033-90 FFC CABLE 17 PINS P1.25 L=200mm J720C
30 17-010-0069-90 FFC CABLE 20 PINS P1.25 L=120mm J604C
31 17-010-0035-90 FFC CABLE 20 PINS P1.25 L=200mm J713C
32 17-010-0036-90 FFC CABLE 28 PIN P1.25 L=160mm J602C,J603C
33 17-010-0037-90 FFC CABLE 28 PINS P1.25 L=200mm J714C
W/ SHIELD
W/ SHIELD
W/ SHIELD
W/ SHIELD
W/SHIELD
10
BLOCK DIAGRAM
11
SPECIAL FUNCTION
FEATURE KEYS PRESS ON FRONT PANEL
RESET FOR AH VERSION VIDEO 6 + SOURCE UP
RESET FOR C VERSION VIDEO 6 + SOURCE DOWN
NTSC / PAL SELECTION VIDEO 6 + MEMORY
VFD ALL DISPLA Y VIDEO 6 + TONE DEFEAT
AM FREQ. STEP AM/FM + FM MUTE
VERSION CHECK VIDEO 6 + TONE CONTROL
DETAILS & WAVEFORMS ON SYSTEM TEST & DEBUGGING
T89C51RB2 (U202) main clock is at 20MHz (X202)
UPPER - OUTPUT ENABLE (pin 24) of EPROM
(W27C02) when changing SURROUND MODES
LOWER - CHIP ENABLE (pin 22) of EPROM
(W27C02) when changing SURROUND MODES
T89C51RD2 (U201) main clock is at 20MHz (X201)
UPPER - +5V supply to KEYBOARD when power up
LOWER - RESET line (TCM810LENB713) when
power up
SCLK (pin 43 of CS49326)
LRCLK (pin 42 of CS49326)
MCLK (pin 30 of CS49326)
NOTE: The waveforms are based on software version V2.12.
12
ADJUSTMENT POINT DIAGRAM
FRONT/CENTER AMPLIFIER BOARD
R522 R545 R571
P501
P502 P503
SURROUND AMPLIFIER BOARD
R835 R836
P801
AMPLIFIER ADJUSTMENT
P802
Idle Current
1. Rotate R522 fully clockwise.
2. Connect DC millivoltmeter to P501 (i.e. Across half of R523, 0.22 Ohm resistor).
3. Turn on the unit.
4. Adjust R522 for 1mV reading on voltmeter.
5. Leave power on for at least 5 min, and check for idle current again.
6. Repeat for other channels.
CHANNEL JUMPER VR
FL P501 R522
FR P502 R545
C P503 R571
SL P801 R835
SR P802 R836
13
PCB LAYOUT
AUDIO BOARD
POWER SUPPLY (STANDBY) /
POWER SWITCH
14
COMPOSITE VIDEO BOARD - COMPONENT SIDE
COMPOSITE VIDEO BOARD - COPPER SIDE
15
COMPONENT VIDEO BOARD - COMPONENT SIDE
COMPONENT VIDEO BOARD - COPPER SIDE
DIGITAL BOARD - COMPONENT SIDE
DIGITAL BOARD - COPPER SIDE
16
DSP BOARD - COMPONENT SIDE
DSP BOARD - COPPER SIDE
17
FRONT / CENTER AMPLIFIER BOARD
18
SURROUND AMPLIFIER BOARD
19
KEYBOARD
- COMPONENT SIDE - COPPER SIDE
20
MAIN BOARD
21
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