NAD T 743 User manual

NAD
SERVICE MANUAL
T 743
T 743
A/V Receiver
A/VReceiver
DRAFT DATE: 12 MAR 2004

2
SAFETY INFORMATION

3
SERVICE SAFETY PRECAUTIONS
1. Replacing the fuses
CAUTION:
FOR CONTINUED PROTECTIONAGAINST THE RISK OF FIRE REPLACE ONLY WITH SAME TYPE OF
FUSE.
Reference Designator Part Number Description
F751*AH 33-0101001-00-48 FUSE 7A 250V TIME-LAG5 X 20mm
SIC UL/CSA
F751*C 33-0141002-00-48 FUSE 4A 250V TIME-LAG 5 X 20mm
VDE/UL TSD
F752*AH 33-0111006-00-48 FUSE 1.6A 250V TIME LAG LBC 5x20mm
TSD UL/CSA/VDE/SEMKO
F752*C 33-0151006-00-48 FUSE 800mA 250V TIME LAG LBC 5x20mm
TSD UL/CSA/VDE/SEMKO
FH751-FH752 33-1000000-00-88 FUSE CLIP 0.05mm FC-53-11
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 supply circuit.
CONTENTS
DESCRIPTION PAGE
SPECIFICATIONS............................................................................................................................ 4 - 5
REAR PANEL / FRONTPANEL VIEW .................................................................................................. 6
DISASSEMBLYINSTRUCTIONS .......................................................................................................... 7
WIRINGDIAGRAM................................................................................................................................ 8
BLOCKDIAGRAM................................................................................................................................. 9
SPECIALFUNCTION .......................................................................................................................... 10
DETAILS & WAVEFORMS ON SYSTEM & TEST & DEBUGGING .................................................... 10
ADJUSTMENT POINTS DIAGRAM /AMPLIFIERADJUSTMENT .......................................................11
PCB LAYOUT ............................................................................................................................... 12 - 23
SCHEMATICDIAGRAM ............................................................................................................... 24 - 40
ICBLOCKDIAGRAM ................................................................................................................... 41 - 46
EXPLODEDVIEW............................................................................................................................... 47
EXPLODED VIEW PARTS LIST................................................................................................... 48 - 49
ELECTRICALPARTS LIST .......................................................................................................... 50 - 62
PACKING DIAGRAM .......................................................................................................................... 63
VERSIONHISTORY .......................................................................................................................... 64
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) 150 ± 20 mV
S/N Ratio (A-wtd, 1kHz, 1 W, 8 ohm, SL/SR/BL) ≥≥
≥≥
≥- 72 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 %
Power output Surround Mode 5 x 50W (16.98 dBW)

5
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 ≤≤
≤≤
≤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 dBuV
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 *AH
Input level is expressed as the reading in open circuit
of 75-ohm source impedance signal generator
Usable sensitivity (98 MHz) ≤≤
≤≤
≤15 dBµV ≤≤
≤≤
≤15 dBuv
S/N Ratio (60 dB, IHF wtd) Mono ≥≥
≥≥
≥63 dB ≥≥
≥≥
≥63 dB
Stereo ≥≥
≥≥
≥63 dB ≥≥
≥≥
≥63 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 ≥≥
≥≥
≥30 dB
1 k ≥≥
≥≥
≥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) −−
−−
−≥≥
≥≥
≥65 dB
I.F. Rejection (10.7 MHz) ≥≥
≥≥
≥78 dB −−
−−
−
Pilot Suppression (98 MHz) ≥≥
≥≥
≥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 −−
−−
−
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)

6
FRONT PANEL
REAR PANEL / FRONT PANEL VIEW
REAR PANEL
1. FM &AMANTENNA
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
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743 WIRE DIAGRAM DATE : 10
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WIRING DIAGRAM

9
BLOCK DIAGRAM

10
SPECIALFUNCTION
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
DETAILS & WAVEFORMS ON SYSTEM TEST & DEBUGGING
T89C51RD2 (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 V1.27.

11
R522 R545 R571
P501
P801
P802
R835 R836
P502 P503
AMPLIFIERADJUSTMENT
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.
ADJUSTMENTPOINTDIAGRAM
FRONT/CENTER AMPLIFIER BOARD
SURROUND AMPLIFIER BOARD

12
PCBLAYOUT
AUDIO BOARD
POWER SUPPLY (STANDBY) /
POWER SWITCH

13
COMPOSITE VIDEO BOARD - COMPONENT SIDE
COMPOSITE VIDEO BOARD - COPPER SIDE

14
COMPONENT VIDEO BOARD - COMPONENT SIDE
COMPONENT VIDEO BOARD - COPPER SIDE
DIGITAL BOARD - COMPONENT SIDE
DIGITAL BOARD - COPPER SIDE

15
DSP BOARD - COPPER SIDE
DSP BOARD - COMPONENT SIDE

16
FRONT / CENTER AMPLIFIER BOARD

17
SURROUND AMPLIFIER BOARD

18
KEYBOARD
- COMPONENT SIDE - COPPER SIDE

19
MAIN BOARD

20
MULTI-CHANNEL BOARD
- COMPONENT SIDE - COPPER SIDE