NAD T744 User manual

NAD
SERVICE MANUAL
T 744
T 744
A/V Receiver
A/V Receiver
DRAFT DATE: 08 MAY2007

2
SAFETY INFORMATION

3
SERVICE SAFETY PRECAUTIONS
1. Replacing the fuses
CAUTION:
FOR CONTINUED PROTECTIONAGAINST THE RISK OF FIRE REPLACE ONLYWITH SAME TYPE OF
FUSE.
Reference Designator Database Part Number Description
F751*AH 20-001-0075-90 FUSE TIME-LAG 7A 250V 5 X 20mm
SIC UL/CSA (RoHS)
F752*AH 20-001-0076-90 FUSE 1.6A 250V TIME LAG LBC 5x20mm
TSD UL/CSA/VDE/SEMKO (RoHs)
F751*C,CT 20-001-0071-90 FUSE TIME-LAG 4A/250V 5 X 20mm
VDE/UL TSD (RoHS)
F752*C,CT 20-001-0069-90 FUSE 800mA 250V TIME LAG LBC
5x20mm TSD UL/CSA/VDE/SEMKO (RoHS)
FH751-FH752 20-002-0030-90 FUSE CLIP 0.05mm WL-210A
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.
CONTENTS
DESCRIPTION PAGE
SPECIFICATIONS............................................................................................................................ 4 - 5
REAR PANEL / FRONTPANEL VIEW .................................................................................................. 6
DISASSEMBLYINSTRUCTIONS .......................................................................................................... 7
WIRING DIAGRAM & PARTS LIST................................................................................................ 8 - 10
BLOCKDIAGRAM................................................................................................................................11
SPECIALFUNCTION .......................................................................................................................... 12
DETAILS & WAVEFORMS ON SYSTEM & TEST & DEBUGGING .................................................... 12
ADJUSTMENT POINTS DIAGRAM /AMPLIFIERADJUSTMENT ...................................................... 13
PCB LAYOUT ............................................................................................................................... 14 - 25
SCHEMATICDIAGRAM ............................................................................................................... 26 - 42
ICBLOCK DIAGRAM ................................................................................................................... 43 - 49
EXPLODEDVIEW............................................................................................................................... 50
EXPLODED VIEW PARTS LIST................................................................................................... 51 - 53
ELECTRICALPARTS LIST ........................................................................................................... 54-66
PACKINGDIAGRAM .......................................................................................................................... 67
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.

4
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 ±±
±±
±20mV
S/N Ratio (A-wtd, 1kHz, 1 W, 8 ohm, SL/SR/BL) ≥≥
≥≥
≥- 75 dB
Frequency Response (20 Hz - 20 kHz) 0 ±±
±±
±1.0 dB
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 ≥≥
≥≥
≥55 dB
Subwoofer out, 500 mV in (THD at 2 V O/P, 100 Hz) ≤0.5 %
Crosstalk (500 mV input, 10 W, 1 kHz) ≥≥
≥≥
≥-57 dB
Controls
Bass (at 500 mV in, 1 W out, 100 Hz) ±±
±±
±10 dB ±±
±±
±2 dB
Treble (at 500 mV in, 1 W out, 10 kHz) ±±
±±
±10 dB ±±
±±
±2 dB
DOLBY DIGITAL SECTION
Channel Difference(FL ref. Track 30) ±±
±±
±1.2 dB
Frequency Resporse at Dolby config.2 SL Track 46 200 - 20 kHz ±±
±±
±0.8 dB
SR Track 47 200 - 20 kHz ±±
±±
±0.8 dB
C Track 44 200 - 20 kHz ±±
±±
±0.8 dB
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 ≥≥
≥≥
≥65 dB
Audio LPF ≥≥
≥≥
≥70 dB
A-WTD ≥≥
≥≥
≥70 dB
Channel Separation (1W,A-WTDFILTER) Track 65 997 Hz ≥≥
≥≥
≥60 dB
DOLBY PRO LOGIC II SECTION
Frequency Resporse
I/P mode : L, R : 1 V in, 1 W, Ch L/R 40 Hz 0 ±±
±±
±2.0 dB
20 kHz 0 ±±
±±
±2.0 dB
I/P mode : L=R : 1 V in, 1 W, Ch /L/R 40 Hz 0 ±±
±±
±2.0 dB
Ch C 20 kHz 0 ±±
±±
±2.0 dB
I/P mode : L=-R : 1 V in, 1 W, Ch SL/SR 40 Hz 0 ±±
±±
±2.0 dB
20 kHz 0 ±±
±±
±2.0 dB
S/N Ratio (200 mV in, 1 W, A-WTD w/ 1 k 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 (2.2 V in, 1 W, w/ 80 kHz LPF, 1 kHz) ≤0.2 %

5
DTS SECTION
Output Level (Vol 0 dB) : FL/FR/C/SL/SR Track 6 1 kHz 2.5 ±±
±±
±0.2 W
Channel Difference (FL ref): FL/FR/C/SL/SR Track 6 1 kHz ±±
±±
±1.0 dB
Harmonic Distortion (Audio Filter) : FL/FR/C/SL/SR Track 10-14 1 kHz ≤≤
≤≤
≤0.08 %
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 ±±
±±
±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) ≤≤
≤≤
≤30 dBµµ
µµ
µV
S/N Ratio (5 mV in) ≥≥
≥≥
≥38 dB
THD (5 mV in) ≤≤
≤≤
≤3 %
IF Rejection (450 kHz) ≥≥
≥≥
≥36 dB
Image Rejection (F+2xIF) ≥≥
≥≥
≥28 dB
Selectivity ≥≥
≥≥
≥17 dB
Output 170 ±±
±±
±20 mV
Loop sensitivity (20 dB S/N)
999/1000 kHz ≤≤
≤≤
≤66 dB
603/600 kHz ≤≤
≤≤
≤66 dB
1404/1400 kHz ≤≤
≤≤
≤66 dB
Frequency Response (100 - 2.3 kHz, 5 mV) ±±
±±
±6 dB
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) ≤≤
≤≤
≤15 dBµµ
µµ
µ≤≤
≤≤
≤15 dBµµ
µµ
µv
S/N Ratio (60 dB, IHF wtd) Mono ≥≥
≥≥
≥63 dB ≥≥
≥≥
≥63 dB
Stereo ≥≥
≥≥
≥63 dB ≥≥
≥≥
≥63 dB
Frequency Response (20 Hz - 15 kHz, 60 dBµµ
µµ
µ)0 ±±
±±
±1.5 dB 0 ±±
±±
±1.5 dB
Channel Separation (60 dBµµ
µµ
µ) 100 Hz ≥≥
≥≥
≥30 dB ≥≥
≥≥
≥30 dB
1 k ≥≥
≥≥
≥38 dB ≥≥
≥≥
≥38 dB
10 kHz ≥≥
≥≥
≥30 dB ≥≥
≥≥
≥30 dB
Alternate Channel Selectivity (40 dBµµ
µµ
µ, ±±
±±
±400 kHz) ≥≥
≥≥
≥60 dB ≥≥
≥≥
≥45 dB
Capture Ratio (40 dBµµ
µµ
µ)≤≤
≤≤
≤3 dB ≤≤
≤≤
≤3 dB
AM Suppression (60 dBµ, 100% Mod. FM, 30% Mod. AM) ≥≥
≥≥
≥48 dB ≥≥
≥≥
≥48 dB
Image Rejection (119.4 MHz) −−
−−
−≥≥
≥≥
≥65 dB
I.F. Rejection (10.7 MHz) ≥≥
≥≥
≥78 dB −−
−−
−
Pilot Suppression (98 MHz) ≥≥
≥≥
≥60 dB ≥≥
≥≥
≥60 dB
THD (60 dBµµ
µµ
µ, 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 dBµµ
µµ
µ≥≥
≥≥
≥24 dBµµ
µµ
µ
Off ≤≤
≤≤
≤15 dBµµ
µµ
µ≤≤
≤≤
≤15 dBµµ
µµ
µ
RDS decode Sensitivity ≤≤
≤≤
≤26 dBµµ
µµ
µ−−
−−
−
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)

6
FRONT PANEL
REAR PANEL / FRONT PANEL VIEW
REAR PANEL
1. FM &AM ANTENNA
2. MONITOR OUT
3. CD INPUT
4. DIGITALAUDIO INPUT &
DIGITALAUDIO OUTPUT
5. SOFTCLIPPING ON/OFF
6. IR INPUT & OUTPUT
7. +12V TRIGGER INPUT & OUTPUT
8. COMPONENT VIDEO IN &
COMPONENT VIDEO OUT
9. AC POWER CORD
10. POWER SWITCH
11. SWITCHEDAC OUTLETS
12. SPEAKERSA& B
13. DVD, SAT, VCR, VIDEO 4 & VIDEO 5
14. MAIN IN /AUDIO PRE-OUTS /
SUBWOOFER OUT
15. TAPE 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)
11. SOURCE DOWN / UP
12. SURROUND MODE
13. LEVELS
14. TONE DEFEAT
15. TONE CONTROLS
16. SPEAKERSA& B
17. VIDEO 6 INPUT
18. PHONES

7
DISASSEMBLY INSTRUCTIONS
1. Remove machine screws M4.0 x 8.0 (1to 6) from the side panels.
Remove tapping screw 3.0 x 8.0 (7to 10) from the back panel.
Refer to 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. 1
Figure No. 2

8
WIRING DIAGRAM
TUNER
J705A
J705B
FROM TRANSFORMER
32
28
30
29
6
8
31 33
2627
2525
24
9
10
12
23
21
20 19
18
17 16
15
14
13
7
4
5
3
21
11
22
FOR T2743 120V VER.FOR T2743 120V VER.
J203A
J713B J714B
J753B
J204B
J713A J714A
J782B
J715A
J720A
J709A
J502B
J704A
J707A
J710A
J717A
J719A
J711A
J715B J604B
J203B
DSP BOARD
J1010B J1009B
J3103B J709B
VIDEO 6 INPUT
LED BOARD
J783A
J782A
J784A
J781A
J786A
J710B J711B
J704B
J414B
J1010A
J1009A
J602B J603B
J707B
J414A
J612A
J611A
J717B
J601B
J719B
J601A J602A J603A
J604A
J751B
J753A
J754B
J753_N J753_L
J759_L
J758_N
J504A
J612A
J502A
J503A
J501A
J505A
J506A
J504B
J781B
J501B
J506A
J503B
J611B
J801A
J204A
J505B
J506B J801B
J350A
J786B
J201
J701
P4401
P4402
J606B
J350B
J3103B
J606B

9
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
L=180mm BD-J504A
2 17-012-2969-90 CABLE ASSY 5 WAYS P3.96 AWG18 UL1007 AMP1
L=200mm BD-J501A
3 17-012-2976-90 CABLE ASSY 12 WAYS AWG=26 2.5P UL2877 AMP1
L=120mm BD-J503A
4 17-012-2959-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1007 AMP2
L=180mm BD-J781B
5 17-012-2966-90 CABLE ASSY 4 WAYS AWG26 2.5P UL1533 AUDIO
L=450MM (ROHS) BD-J3103A
6 17-012-2957-90 CABLE ASSY 2 WAYS AWG=26 2.5P UL1533 DIGIT BD-
L=540mm (ROHS) J1009A
7 17-012-2961-90 CABLE ASSY 3 WAYS AWG=26 X2C P=2.5 DIGITAL BD-
UL2854 L=110mm C33110 (RoHS) J705A
8 17-012-2967-90 CABLE ASSY 4 WAYS AWG=26 2.5P DIGITAL BD-
UL2877 L=500mm (RoHS) J1010A
9 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK KEYBOARD-
L=100mm W/ RING TERMINAL (RoHS) J201
10 17-012-3404-90 CABLE ASSY 5 WAYS AWG26 2.5P UL1007 LED BD-
L=160mm (RoHS) J204A
11 17-012-2963-90 CABLE ASSY 3 WAYS AWG=26 2.5P L=110mm MAIN BD-
J606B
12 17-012-2964-90 CABLE ASSY 3 WAYS AWG26X2C UL2547 MAIN BD-
L=210mm (UL LABEL) (RoHS) J715A
13 17-012-2974-90 CABLE ASSY 8 WAYS AWG=26X3C L=480mm MAIN BD-
(RoHS) J709A
14 17-012-2977-90 CABLE ASSY 12 WAYS AWG26 2.5P UL2468 MAIN BD-
L=230mm (UL LABEL) (RoHS) J502A
15 17-012-2978-90 CABLE ASSY 14 WAYS AWG=26 2.5P UL1007 MAIN BD-
L=440mm (UL LABEL) (RoHS) J782B
16 17-012-2962-90 CABLE ASSY 3 WAYS AWG=26 2.5P UL2854 PO BD-
L=420mm (RoHS) J611A
17 17-012-2972-90 CABEL ASSY 6 WAYS AWG=26 2.5P PO BD-
UL1533X1C L=350mm (RoHS) J612A
18 17-012-2965-90 CABLE ASSY 4 WAYS AWG26 2.5P UL2468 PS BD-
L=400mm (ROHS) J753A
19 17-012-2958-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1007 SPK
L=120mm BD-J801B
20 17-012-2960-90 CABLE ASSY 3 WAYS AWG=18 3.96P UL1015 SPK BD-
L=320mm J505B
21 17-012-2968-90 CABLE ASSY 5 WAYS AWG=18 3.96P UL1007 SPK BD-
L=350mm J786B
22 17-012-2970-90 CABLE ASSY 5 WAYS AWG18 UL1007 SPK BD-
L=300mm (V/B/Y) (UL LABEL) (RoHS) J506B
23 17-012-2973-90 CABLE ASSY 8 WAYS AWG=26 2.5P UL1007 SV BD-
L=380mm (RoHS) J414A
24 17-012-2975-90 CABLE ASSY 8 WAYS AWG=26 2.5P UL1007 TR BD-
L=540mm (UL LABEL) (RoHS) J350A
25 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK V6 BD-
L=100mm W/ RING TERMINAL (RoHS) P4401,P4402
26 17-012-2948-90 CABLE ASSY 1 WAY AWG=16 UL1672 J759
BROWN L=100mm
27 17-012-2874-90 CABLE ASSY 1 WAY AWG=16 UL1672 J758
BLUE L=100mm
28 17-010-0032-90 FFC CABLE 30 PINS P1.25 L=70mm J601A
W/SHIELD

10
Item Database Part Number Description Remark
29 17-010-0033-90 FFC CABLE 17 PINS P1.25 L=200mm J720C
W/ SHIELD
30 17-010-0069-90 FFC CABLE 20 PINS P1.25 L=120mm J604C
W/ SHIELD
31 17-010-0035-90 FFC CABLE 20 PINS P1.25 L=200mm J713C
W/ SHIELD
32 17-010-0036-90 FFC CABLE 28 PIN P1.25 L=160mm J602C,J603C
W/ SHIELD
33 17-010-0037-90 FFC CABLE 28 PINS P1.25 L=200mm J714C
W/SHIELD

11
BLOCK DIAGRAM

12
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 ALLDISPLAY 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)
T89C51RD2 (U201) main clock is at 20MHz (X201)
UPPER - +5V supply to KEYBOARD when power up
LOWER - RESET line (TCM810LENB713) when
power up
UPPER - OUTPUT ENABLE (pin 24) of EPROM
(W27C02) when changing SURROUND MODES
LOWER - CHIP ENABLE (pin 22) of EPROM
(W27C02) when changing SURROUND MODES
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.

13
R522 R545 R571
P501
P801
P802
R835 R836
P502 P503
AMPLIFIER ADJUSTMENT
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
ADJUSTMENT POINT DIAGRAM
FRONT/CENTER AMPLIFIER BOARD
SURROUND AMPLIFIER BOARD

14
PCB LAYOUT
AUDIO BOARD
POWER SUPPLY (STANDBY) /
POWER SWITCH

15
COMPOSITE VIDEO BOARD - COMPONENT SIDE
COMPOSITE VIDEO BOARD - COPPER SIDE

16
COMPONENT VIDEO BOARD - COMPONENT SIDE
COMPONENT VIDEO BOARD - COPPER SIDE
DIGITAL BOARD - COMPONENT SIDE
DIGITAL BOARD - COPPER SIDE

17
DSP BOARD - COPPER SIDE
DSP BOARD - COMPONENT SIDE

18
FRONT / CENTER AMPLIFIER BOARD

19
SURROUND AMPLIFIER BOARD

20
KEYBOARD
- COMPONENT SIDE - COPPER SIDE