NAD T-743 Service manual
DRAFT DATE: 12 MAR 2004
NAD
SERVICE MANUAL
T 743
A/V Receiver
T 74 3
A/V Receiver
SAFETY INFORMA TION
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 Part Number Description
F751*AH
F751*C
F752*AH
F752*C
FH751-FH752
NOTE: <*AH > : USA, CANADIAN MODEL ONL Y.
<*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 supply circuit.
33-0101001-00-48 FUSE 7A 250V TIME-LAG5 X 20mm
SIC UL/CSA
33-0141002-00-48 FUSE 4A 250V TIME-LAG 5 X 20mm
VDE/UL TSD
33-0111006-00-48 FUSE 1.6A 250V TIME LAG LBC 5x20mm
TSD UL/CSA/VDE/SEMKO
33-0151006-00-48 FUSE 800mA 250V TIME LAG LBC 5x20mm
TSD UL/CSA/VDE/SEMKO
33-1000000-00-88 FUSE CLIP 0.05mm FC-53-11
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 P ANEL VIEW .................................................................................................. 6
DISASSEMBL Y INSTRUCTIONS.......................................................................................................... 7
WIRING DIAGRAM................................................................................................................................ 8
BLOCK DIAGRAM................................................................................................................................. 9
SPECIAL FUNCTION .......................................................................................................................... 10
DETAILS & WAVEFORMS ON SYSTEM & TEST & DEBUGGING .................................................... 10
ADJUSTMENT POINTS DIAGRAM / AMPLIFIER ADJUSTMENT .......................................................11
PCB LAYOUT............................................................................................................................... 12 - 23
SCHEMA TIC DIAGRAM ............................................................................................................... 24 - 40
IC BLOCK DIAGRAM ................................................................................................................... 41 - 46
EXPLODED VIEW............................................................................................................................... 47
EXPLODED VIEW PAR TS LIST................................................................................................... 48 - 49
ELECTRICAL P AR TS LIST .......................................................................................................... 50 - 62
PACKING DIAGRAM.......................................................................................................................... 63
VERSION HISTORY .......................................................................................................................... 64
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 %
Power output Surround Mode 5 x 50W (16.98 dBW)
Input Sensitivity (ref. 8 ohms, 1 kHz) 150 ± 20 mV
S/N Ratio (A-wtd, 1kHz, 1 W, 8 ohm, SL/SR/BL)
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
Subwoofer out, 500 mV in (THD at 2 V O/P, 100 Hz) ≤ 0.5 %
Crosstalk (500 mV input, 10 W, 1 kHz)
≥≥
≥ - 72 dB
≥≥
≥≥
≥ 55 dB
≥≥
≥≥
≥ -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
Audio LPF
A-WTD
Channel Separation (1 W, A-WTD FILTER) Track 65 997 Hz
≥≥
≥ 65 dB
≥≥
≥≥
≥ 70 dB
≥≥
≥≥
≥ 70 dB
≥≥
≥≥
≥ 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
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
≥≥
≥ 65 dB
≥≥
≥≥
≥ 65 dB
≥≥
≥≥
≥ 65 dB
≥≥
DTS SECTION
Output Level (Vol 0 dB) : FL/FR/C/SL/SR Track 6 1 kHz 0.9 ± 1.3 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
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
≤≤
≤ 0.08 %
≤≤
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 ± 20 mV
Loop sensitivity (20 dB S/N)
999/1000 kHz
603/600 kHz
1404/1400 kHz
Frequency Response (100 - 2.3 kHz, 5 mV) ± 6 dB
≤≤
≤ 30 dBuV
≤≤
≥≥
≥ 38 dB
≥≥
≤≤
≤ 3 %
≤≤
≥≥
≥ 36 dB
≥≥
≥≥
≥ 28 dB
≥≥
≥≥
≥ 17 dB
≥≥
≤≤
≤ 66 dB
≤≤
≤≤
≤ 66 dB
≤≤
≤≤
≤ 66 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)
S/N Ratio (60 dB, IHF wtd) Mono
Stereo
Frequency Response (20 Hz - 15 kHz, 60 dBµ) 0 ± 1.5 dB 0 ± 1.5 dB
Channel Separation (60 dBµ) 100 Hz
1 k
10 kHz
Alternate Channel Selectivity (40 dBµ, ± 400 kHz)
Capture Ratio (40 dBµ)
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 dBµ, L=R 75 kHz for AH, 40 kHz Dev for C) Mono
Stereo
Auto-Search Sensitivity On
Off
RDS decode Sensitivity
≤≤
≤ 15 dBµV
≤≤
≥≥
≥ 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 dBµ
≥≥
≤≤
≤ 15 dBµ
≤≤
≤≤
≤ 26 dBµ
≤≤
≤≤
≤ 15 dBuv
≤≤
≥≥
≥ 63 dB
≥≥
≥≥
≥ 63 dB
≥≥
≥≥
≥ 30 dB
≥≥
≥≥
≥ 38 dB
≥≥
≥≥
≥ 30 dB
≥≥
≥≥
≥ 45 dB
≥≥
≤≤
≤ 3 dB
≤≤
≥≥
≥ 48 dB
≥≥
≥≥
≥ 65 dB
≥≥
−−
−
−−
≥≥
≥ 60 dB
≥≥
≤≤
≤ 0.25 %
≤≤
≤≤
≤ 0.35 %
≤≤
≥≥
≥ 24 dBµ
≥≥
≤≤
≤ 15 dBµ
≤≤
−−
−
−−
PHYSICAL SPECIFICATIONS
Dimensions (Width x Height x Depth) 435 x 167 x 382 mm
Net Weight 18.50 Kg (40.70 lbs)
Shipping Weight 22.20 Kg (48.84 lbs)
5
REAR PANEL / FRONT PANEL VIEW
REAR PANEL
1. FM & AM ANTENNA
2. MONITOR OUT
3. CD INPUT
4. DIGITAL 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
O
O
D
BOARD
O
O
O
O
O
O
O
O
O
O
SU
C
OU
O
D
.
O
05
/
/
.
FRO
SFO
05
6
35
0
SS
5
S
6
U
68
50
08
6
35
00
SS
8
S
6
U
8
80
SSY
0
6
35
05
SS
S
6
U
68
00
03
8
35
03
SS
3
S
8
U
00
80
05
8
38
0
SS
5
35
0
SS
S
6
U
8
0
03
6
35
03
SS
3
S
6
.5
85
50
0
6
35
0
SS
S
6
U
8
500
0
6
35
0
SS
S
6
U
533
5
0
0
6
35
00
SS
S
6
U
8
00
0
8
C
C
0
S
.
5
0
8
0
C
C
S
.
5
00
03
6
35
06
SS
3
S
6
U
85
50
0
8
0
C
C
0
S
.
5
00
C
C
8
S
.
5
00
03
8
35
03
SS
3
S
8
9
06
6
35
0
SS
6
S
6
U
533
350
08
6
35
00
M
06
6
35
03
SS
6
S
6
U
8
80
6
35
00
SS
S
6
U
8
0
M
03
8
35
0
SS
3
S
8
03
8
35
05
SS
3
S
8
8
8
C
C
8
.
5
0
8
8
C
C
8
.
5
0
30
806
C
C
30
S
.
5
60
SS
3
S
6
U
85
00
SS
S
6
.5
U
8
0
0
6
38
03
C
6
U
6
U
00
0
6
36
SS
6
U
6
O
00
0
8
35
00
SS
8
/
G
0
8
35
0
SS
8
00
C
360
m
05
8
35
03
SS
5
S
8
U
00
300
SS
5
S
8
U
00
350
0
8
35
00
SS
8
/
G
03
3
53
0
0
5
0
0
0
9
5
03
O
0
0
O
6
U
O
D
O
83
8
8
8
86
0
B
5
5
B
J753_N5J
_
_
8
0
0
0
WIRING DIAGRAM
HANNEL
LTI-
A
2A
1A
A
EV
04
03
NER
2
P1
1-71-XX
2
ABLE 17 PIN
-172
F
MM
=2
2
P1
PIN
121-71-XX
2
ABLE 2
-2
F
#2
#2
4-XX
Y 2 WAY
1
MM
22
ABLE A
2-
=12
MM
MM
4
2-XX
L=
Y 4 WAY
77 L=
1
L2
L1
42
P
P
ABLE A
2-
PIN
mm
PIN
141-71-XX
2
ABLE 2
-2
F
12A
B
7
PIN
mm
141-71-XX
2
ABLE 2
L=14
2
-2
1
F
11A
ARD
B
DI
B
ARD
B
-VIDE
1-71-XX
mm
2
ABEL
L=
2
-
L=14
2
1
AR
T B
RE-
1
F
717B
1B
#2
WAY
2-XX
Y
1
2
ABLE A
2-
2B
P
2
#2
-XX
MM
WAY
-
Y
1
4 L=1
2
L2
ABLE A
2-
A
72
A
MM
L=
L1
P
711A
4A
7
71
2B
A
A
A
71
ARD #1
B
MP
A
71
ARD
717A
AIN B
721A
#2
MM
2-XX
Y 12 WAY
77 L=12
L2
P
ABLE A
2-12241
A
1A
#2
MM
-XX
WAY
-
4 L=2
Y
1
L2
2
P
ABLE A
2-
m
1-XX
K L=
Y 1 WAY #1
4
7 BLA
11
RING TERMINAL
L1
ABLE A
2-
709A
#2
M
-XX
Y 12 WAY
77 L=24
1
L2
P
ABLE A
2-122
502A
1
7
4A
12A
1009B
B
2
1
2
2A
7
A
2
B
1
1
ARD
P B
B
4B
71
-XX
4
11
2-
743 WIRE DIAGRAM DATE : 10
-XX
MM
Y 4 WAY
1
77 L=2
42
L2
2-
ABLE A
2
TERMINAL
IN
Y 1 WAY AWG1
ABLE A
L1007 BLACK L=100mm W
PIN
MM
ABLE 2
L=2
2
1
B
F
71
PIN
MM
1-71-XX
2
2
ABLE 2
L=2
2
-2
1
F
B
#1
-XX
WAY
Y
2
1
ABLE A
2-
-XX
MM
Y 4 WAY
1
L=4
42
L24
2-
ABLE A
2
1B
A
6P UL1007 L=180MM
.
#2
1A
7
7
ARD
B
IDE
ARD
IGITAL B
414B
AR
PEAKER B
NENT
MP
ARD
B
IDE
mm
#1
WAY
7 L=
Y
L1
P
ABLE A
2-XX
2
1
#1
2-
-XX
WAY
Y
2
1
ABLE A
2-
.96P UL1015 L=320mm
ABLE A
#1
WAY
Y
ABLE A
.96P UL1007 L=120mm
WN
-12-XX
Y 1 WAY
4
72 BR
11
L1
2-
ABLE A
1
77
L2
#2
-XX
WAY
Y
1
MM
2
ABLE A
2-
=4
72
mm
ABLE
L1
-XX
E L=1
-
L
4
Y 1 WAY #1
11
2-
mm
WAY
4 L=7
Y
L2
P
ABLE A
2-0326135-02-98
mm
=1
-XX
2
1
2-
#1
WAY
Y
ABLE A
L
759
11B
mm
7 L=
L1
P
N
4
758
7
PPLY
ARD #1
753_L
WER
1B
7
8
1-XX
Y
2
1
AYS #18 3.96P
ABLE A
2-
MM
#1
-XX
WAY
7 L=1
Y
2
L1
1
P
ABLE A
2-
1B
7
1A
4A
7
A
7
7
A
7
2A
7
ECONDARY BOARD
2-1426135-00-98
-XX
1
2
ABLE ASSY 8 WAYS #26 2.5P UL2877 L=480M
2-
-XX
MM
#2
1
WAY
2
77 L=4
Y
mm
L2
2-
P
ABLE A
77 L=42
L2
P
2
#2
Y 14 WAY
ABLE A
B
7
B
4B
2
-XX
Y 1 WAY #1
4
TERMINAL
11
L1007 BLACK L=100mm W
ABLE A
IN
2-
AR
T B
INP
IDE
MM
WAY
1-XX
-
L=1
Y
1
L24
2
ABLE A
2-
2
ARD
4A
2
ED B
M TRAN
RMER
BLOCK DIAGRAM
9
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 + MEMORY
VFD ALL DISPLAY AUDIO 6 + TONE DEFEAT
AM FREQ. STEP AM/FM + FM MUTE
DET AILS & W A VEFORMS ON SYSTEM TEST & DEBUGGING
T89C51RD2 (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 V1.27.
10
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
ISC Sensitivity
1. Connect 8 ohm loading to all channels.
2. Rotate R881 fully clockwise.
3. Load all channels at full power using 1kHz sine wave.
4. At this time, monitor the THD of the SL,SR output. Clipping should occur before full power achieved.
5. The procedure is finish at this step.
6. Load all channels at full power using 1kHz sine wave with 4 ohm load.
7. The clipping power(at THD 0.1%) should less than 85W.
11
PCB LA YOUT
AUDIO BOARD
POWER SUPPLY (STANDBY) /
POWER SWITCH
12
COMPOSITE VIDEO BOARD - COMPONENT SIDE
COMPOSITE VIDEO BOARD - COPPER SIDE
13
COMPONENT VIDEO BOARD - COMPONENT SIDE
COMPONENT VIDEO BOARD - COPPER SIDE
DIGITAL BOARD - COMPONENT SIDE
DIGITAL BOARD - COPPER SIDE
14
DSP BOARD - COMPONENT SIDE
DSP BOARD - COPPER SIDE
15
FRONT / CENTER AMPLIFIER BOARD
16
SURROUND AMPLIFIER BOARD
17
KEYBOARD
- COMPONENT SIDE - COPPER SIDE
18
MAIN BOARD
19
MULTI-CHANNEL BOARD
- COMPONENT SIDE - COPPER SIDE
20
Loading...