NAD T742 User manual

NAD
T 742
SURROUND
SOUND RECEIVER
T 742 SURROUND SOUND RECEIVER
SERVICE MANUAL
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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
M270 *AH 5120-0200-0 5A TIME-LAG 5x20 UL/CSA
M271 *C 5120-0024-0 3.15A TIME-LAG 5x20 VDE-SEMKO
M272 *AH 5120-0052-0 1.6A TIME-LAG 5x20 UL/CSA
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) ±9dB
Treble (at 500mV in, 1W out, 10 kHz) ±9dB
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) ≥45 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 RATING
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
REAR PANEL / FRONT PANEL
REAR PANEL
FRONT PANEL
1. FM & AM ANTENNA
2. TAPE 1 & CD INPUTS
3. 5.1 CHANNEL INPUTS
4. DVD - SAT VCR - VIDEO 4 (AUDIO &
VIDEO)
5. DIGITAL AUDIO INPUTS
6. AUDIO PRE OUTS / SUBWOOFER OUT
7. MONITOR OUT
8. SPEAKERS: FRONT, CENTER & SUR-
ROUND SPEAKERS
9. SOFT CLIPPING
10. IR INPUT
11. AC POWER CORD
12. 12 VOLT TRIGGER OUT
1. POWER
2. STAND-BY INDICATOR
3. DISPLAY
4. FM/AM
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. AUDIO & VIDEO INPUT SELECTORS
13. CD
14. TAPE MONITOR
15. EXT. 5.1
16. SURROUND MODE
17. SET UP
18. TONE CONTROLS

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
P702
P701
POWER SWITCH PCB
J401A
AC3 PCB
J203B
J101A
J604B
J601B
J208A
J208B
J203A
J206A J207A
J207B
SECONDARY PCB
J701A J202B J206A
JP210
JP211
J702B
JP210
J602B
T201A T202A
JP207
JP206
M704B
C230
JP209
JP203
J206B
JP204
JP205
C221
P261
P260 P262
J101B
J203B
J202A
J201B
P264
PSU PCB
P266
P265
DIGITAL PCB
P261
SPEAKER PCB
P262 P260
POWER CORD
L
N
M705A
JP212B
J206B
J705B
J702A
J701B
MAIN PCB
-35V
J705B
J602A
J601A J706B
+35V GND
J401B
M708A
M707A
J604A
J704A
J706B
J709B
J714A
J716A
J715A
J710B
JP207B
J703A
J710B J709B
J704B
J703B
J715B
J714B
J716B
VIDEO 5 PCB
POWER LED PCB
KEYBOARD
J202A J201A
VOL PCB
S-VIDEO PCB
PRIMARY PCB
AMPLIFIER PCB
SURROUND
MULTI CHANNEL PCB
TUNER PCB
AUDIO PCB
VIDEO PCB
SHOWN THE PIN 1 OF WIRE HARNESS
SHOWN THE WAFERS
SHOWN THE SOLDER END OF HARNESS
NOTES :
WIRING DIAGRAM

910
OSC RF
VT
BLOCK DIAGRAM
COAXIAL x2 OPTICAL x1
74HC153
4053
74LS157
M62446FP
S-Video Selector CD4052
TEMPERATURE PROTECTION
TUNER
L
TUNER R
POWER DOWN Detect Pin. For SPK off, Mute ON, VFD off.
FL
Trigger out
IR IN
FL
OUT2 OUT3 OUT1 OUT4
FR CENTER SL SR SUB
FR CENTER SL SR SUB
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
Video Selector CD4051
ADJUSTMENT POINTS DIAGRAM
1. TUNER
2. IDLE CURRENT - Front Amplifier & Surround Amplifier Board

11

12
ALIGNMENT PROCEDURES
AMPLIFIER SECTION
Idle Current
Step Item Connection Adjustment Adjust for
1Front Left Channel Voltmeter to M714 on Main Board VR7703 1mV±0.2mV
2Front Right Channel Voltmeter to M713 on Main Board VR7702 1mV±0.2mV
3Center Channel Voltmeter to M712 on Main Board VR7701 1mV±0.2mV
4Rear Left Channel Voltmeter to TP202 on Surround Amplifier Board VR202 1mV±0.2mV
(PCB N0A00C-AMP2)
5Rear 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
VOLTMETER
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
1DC voltmeter L941 0±100mV
3Distortion
analyzer
Distortion
analyzer
Oscilloscope
Oscilloscope
L942
R956
R941
Minimum
Minimum
2AC 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 fur-
ther 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 RDS-
Program 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 ver-
sion
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