NAD T755 User manual

NAD
SERVICE MANUAL
T 755
T 755
Surround Sound
Receiver
Surround Sound Receiver
DRAFT DATE: AUGUST 2009

2
SAFETY INFORMATION
Manufactured under license under U.S. Patent #’s: 5,451,942; 5,956,674; 5,974,380;
5,978,762; 6,226,616; 6,487,535; 7,003,467; 7,212,872 & other U.S. and worldwide
patents issued & pending. DTS is a registered trademark & the DTS logos and Symbol
are trademarks of DTS, Inc. © 1996-2007 DTS, Inc. All Rights Reserved.
NAD ELECTRONICS INTERNATIONAL
633 GRANITE COURT, PICKERING,ON, CANADA L1W 3K1
MODEL T755 AV SURROUND SOUND RECEIVER
POWER RATING 120V 60Hz 6A
DESIGNED & ENGINEERED IN CANADA, CUSTOM
MANUFACTURED TO NAD SPECIFICATIONS IN CHINA
MODEL T755 AV SURROUND SOUND RECEIVER
NAD ELECTRONICS INTERNATIONAL
POWER RATING 230V 50Hz 3A
DESIGNED & ENGINEERED IN CANADA, CUSTOM
MANUFACTURED TO NAD SPECIFICATIONS IN CHINA

3
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
F8001*AH 20-001-0072-90 FUSE TIME-LAG 6.3A 250VAC
5X20mm TSD UL/CSA/VDE/CCC
WALTER
F8001*C,CT 20-001-0072-90 FUSE TIME-LAG 6.3A 250VAC
5X20mm TSD UL/CSA/VDE/CCC
WALTER
F8002*AH 20-001-0076-90 FUSE 1.6A 250V TIME LAG LBC
5X20mm TSD
UL/CSA/VDE/SEMKO
F8002*C,CT 20-001-0069-90 FUSE TIME-LAG 800mA 250V 5x20mm
TSD UL/CSA/VDE/CCC WALTER
5X20mm VDE/UL/CSA 5T
NOTE:
<*AH > : USA, CANADIAN MODEL ONLY.
<*C, *CT > : EUROPEAN MODEL ONLY.
2. Safety check out
(Only U.S.A. model)
Parts marked with the symbol are critical with regard to the risk of fire and electric shock.
CONTENTS
DESCRIPTION PAGE
SPECIFICATIONS..............................................................................................................................4 - 5
REAR PANEL / FRONT PANEL VIEW ...................................................................................................6
DISASSEMBLY INSTRUCTIONS ...........................................................................................................7
WIRING DIAGRAM ............................................................................................................................8 - 9
BLOCK DIAGRAM.................................................................................................................................10
SPECIAL FUNCTION ..........................................................................................................................11
DETAILS & WAVEFORMS ON SYSTEM & TEST & DEBUGGING................................................11-12
ADJUSTMENT POINTS DIAGRAM / AMPLIFIER ADJUSTMENT.......................................................13
PCB LAYOUT..................................................................................................................................14- 28
SCHEMATIC DIAGRAM...................................................................................................................29-47
ELECTRICAL PARTS LIST..............................................................................................................48-67
IC BLOCK DIAGRAM.......................................................................................................................68-86
EXPLODED VIEW............................................................................................................................87-88
EXPLODED VIEW PARTS LIST ......................................................................................................89-91
SINGLE AMPLIFIER CHANNEL REPAIR KIT .................................................................................92-93
PACKING DIAGRAM.............................................................................................................................94

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) ≤0.1 %
Input Sensitivity (ref. 8 ohms, 1 kHz) 1±0.1 V
S/N Ratio (A-wtd, 1kHz, 1 W, 8 ohm, FL/C/FR/SL/SR) ≥- 80 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, 1 W, 1 kHz) ≥-54 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 (31 for O/P 1 W, Track 35) CCIR / ARM ≥65 dB
Audio LPF ≥64 dB
A-wtd ≥68 dB
Channel Separation (1 W, 20 kHz LPF) Track 65 997 Hz ≥55 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
20Hz 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 ≥60 dB
I/P mode : L=R : 1 kHz, Ch C ≥60 dB
I/P mode : L=-R : 1 kHz, Ch SL/SR ≥60 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 0.5 -0.2/+0.8 W
Channel Difference (FL ref) : FL/FR/C/SL/SR Track 6 1 kHz 0 ±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 dB
Subwoofer Output Level 1 kHz ref at pre-out (FL) Play Track 10, charge to 15 12.5 ±1.5 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) ≤60 dBμV
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/+30 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 dBμ≤15 dBμv
S/N Ratio (60 dB, IHF wtd) Mono ≥60 dB ≥60 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
1k ≥32 dB ≥32 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) ≥50 dB ≥50 dB
THD (60 dBμ, L=R 75 kHz for AH, 40 kHz Dev for C) Mono ≤0.5 % ≤0.5 %
Stereo ≤0.5 % ≤0.5 %
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 160 x 393 mm
Net Weight 17.9 Kg (39.38 lbs)
Shipping Weight 22.7 Kg (49.94 lbs)

6
FRONT PANEL
REAR PANEL / FRONT PANEL VIEW
REAR PANEL
1. IR IN/OUT
2. +12V TRIGGER OUT
3. SOFT CLIPPING
4. FM,AM ANTENNA INPUT
5. XM MODULE INPUT(AH)
DAB MODULE INOUT(C,CT)
6. MP DOCK
1. POWER BUTTON
2. STANDBY LED
3. INFO
4. AM/FM/DB
5. TUNER MODE
6. MEMORY
7. NAVIGATION AND
ENTER BUTTON
8. VACUUM FLUORESCENT
DISPLAY(VFD)
9. REMOTE SENSOR
10. VOLUME
11. SPEAKERS A, B
12. SOURCE
13. LISTENING MODE
14. TONE CONTROLS
15. TONE DEFEAT
16. FRONT INPUT/MP
17. PHONES
18. FRONT INPUT JACKS
19. MC/MIC INPUTS
7. RS-232
8. COMPONENT IN/OUT
9. AUDIO/VIDEO 1~6 IN
10. AUDIO/VIDEO 3/4 OUT
11. MONITOR(S-VIDEO,VIDEO)
12. ZONE 2
13. 7.1 CH INPUT
14. AUDIO PREOUT
15. DIGITAL AUDIO IN/OUT
16. HDMI
17. SPEAKERS A, SPEAKER B
18. AC POWER INLET
19. SWITCHED AC OUTLET
20. POWER

7
DISASSEMBLY INSTRUCTIONS
1. Remove machine screws M4.0 x 8.0 (x 6pcs) from the side panels.
Remove tapping screw 3.0 x 8.0 (x 4pcs) from the back panel.
Refer to Figure No. 1.
2. Pull both sides of the TOP COVER slightly outwards and tilt approx. 35 ° and then
remove in the direction as indicated. Refer to Figure No. 2.
Figure No. 1
Figure No. 2

8
WIRING DIAGRAM

9
WIRING DIAGRAM PARTS LIST
Item Database Part Number Description Remark
1 17-012-3379-90 CABLE ASSY 2 WAYS AWG18 3.96P UL1007 MAIN BD-
L=250mm(RoHS) J7004A
2 17-012-3380-90 CABLE ASSY 3 WAYS AWG18 3.96P UL1007 MAIN BD-
L=250mm(RoHS) J7005A
3 17-012-3382-90 CABLE ASSY 10 WAYS AWG26 2.5P UL1533 MAIN BD-
L=300mm(RoHS) J6005A
4 17-012-3575-90 CABLE ASSY 5 WAYS AWG18 3.96P UL1007 MAIN BD-
L=230mm (RoHS) J7003A
5 17-012-3579-90 CABLE ASSY 6 WAYS AWG26 2.5P UL1533 MAIN BD-
L=80mm (RoHS) J2006A
6 17-012-3974-90 CABLE ASSY 10WAYS AWG#26 2.5P UL1007 MAIN BD-
L=110mm BOTH SIDE SOLDER (RoHS) J6010A/B
7 17-012-4274-90 CABLE ASSY 12 WAYS AWG26 2.5P UL1533 MAIN BD-
2.5P L=350mm (RoHS) J4002A
8 17-012-4275-90 CABLE ASSY 8 WAYS AWG26 UL1533 2.5P MAIN BD-
L=140mm (RoHS) J2009A
9 17-012-3571-90 CABLE ASSY 4 WAYS AWG26 2.5P L=120mm PSU BD-
(RoHS) J2008B
10 17-012-3943-90 CABLE ASSY 1 WAY AWG16 UL1672 BLUE PSU BD-
L=140mm FASTON 4.8mm (RoHS) J8011
11 17-012-3944-90 CABLE ASSY 1 WAY AWG16 UL1672 BROWN PSU BD-
L=140mm FASTON 4.8mm (RoHS) J8012
12 17-012-3578-90 CABLE ASSY 3 WAYS AWG18 3.96P UL1007 SURR AMP BD-
L=120mm (RoHS) J5003B
13 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK DSP BD-
L=100mm W/ RING TERMINAL J6010A
14 17-012-3971-90 CABLE ASSY 20 WAYS AWG28 UL2651 L=120mm KEY BD-
PCB MOUNT (RoHS) J2002B
15 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK SPK BD-
L=100mm W/ RING TERMINAL J8001
16 17-012-3383-90 CABLE ASSY 5 WAYS AWG=18 3.96P UL1007 SPK BD-
L=350mm(V/B/Y/O/R)(RoHS) J7006
17 17-012-3576-90 CABLE ASSY 3 WAYS AWG18 3.96P UL1007 SPK BD-
L=420mm (RoHS) J5602
18 17-012-3577-90 CABLE ASSY 5 WAYS AWG18 3.96P UL1007 SPK BD-
L=340/380/400mm (RoHS) J5304
19 17-012-3385-90 CABLE ASSY 26 WAYS AWG28 UL2651 L=150mm TRIGGER BD-
PCB MOUNT(RoHS) J2007B
20 17-012-4276-90 CABLE ASSY 20 WAYS AWG28 UL2651 L=200mm COMP.VID. BD-
PCB MOUNT (RoHS) J4001B
21 17-012-3168-90 CABLE ASSY 10 WAYS AWG26 UL1007 2.5P HDMI BD-
L=160mm (RoHS) J4306A
22 17-012-2956-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK FRONT INPUT
L=100mm W/ RING TERMINAL BD-J9301
23 17-012-2874-90 Cable assy 1 way AWG=16 UL 1672 blue L=100mm J8017,J8019
(RoHS)
24 17-012-2875-90 CABLE ASSY 1 WAY AWG16 UL 1015 CHASSIS GND,
GREEN/YELLOW L=100mm (RoHS) AC OUTLET
GND
25 17-012-3572-90 CABLE ASSY 20 WAYS AWG28 UL2651 L=80mm J2005C
(RoHS)
26 17-012-3573-90 CABLE ASSY 20 WAYS AWG28 UL2651 L=130mm J2001C
(RoHS)
27 17-012-3948-90 CABLE ASSY 1 WAY AWG16 UL1672 BROWN J8016,J8018
L=100mm (RoHS)
28 17-010-0165-90 FFC CABLE 17 PINS P1.25 L=80MM (RoHS) J6003C

10
BLOCK DIAGRAM

11
SPECIAL FUNCTION
Function Keys Notes
Factory Reset AH Source Down + Front/MP
Factory Reset C Source UP + Front/MP
Toggle IR Channel Source Down + Power
Check MCU & DSP Version Source Down + Source UP
Check Current Video Mode Source Down + Tone Controls
MIC Test Source Down + Tone Defeat
VFD Test Source Down + INFO
PAL/NTSC Source Down + Memory
DAB/XM Source Down + Tuner Band Must cycle power before change takes effect.
9k/10k Source UP + Tuner Band Must reselect AM before change takes effect.
XM 1kHz Test Tone Tuner Band + Tuner Mode XM must be selected first.
XM Signal Strength Tuner Mode for 0.5 seconds XM must be selected first.
XM Diagnostics Mode Tuner Mode for 3 seconds XM must be selected first.
Check DAB Module Version Tuner Mode for 3 seconds DAB must be selected first.
Enter Diagnostics Mode Source Down + Enter
Diagnostic Mode Down Source Down + Cursor Right
Diagnostic Mode Up Source Down + Cursor Left
Power Off All Zones Power Toggle or Power Off for 3 seconds
DETAILS & WAVEFORMS ON SYSTEM TEST & DEBUGGING
U1001 Pin 17 - X1001C output, 24.576MHz
U1001 Pin 2 - Master clock (Analog), 12.288MHz
U1001 Pin 70 - Clock for external memory, 100MHz
U1001 Pin 2 - Master clock (PCM), 11.2896MHz
U1001 Pin 12 - Left/Right clock (Analog), 48kHz U1001 Pin 12 - Left/Right clock (PCM), 44.1kHz

12
U1001 Pin 9 - Serial clock (Analog), 3.072MHz U1001 Pin 9 - Serial clock (PCM), 2.8224MHz
U2001 Pin 12 - X2001A output, 20.000MHz U4520 Pin 7 - X4503 output, 13.500MHz
U4507 Pin 75 - X4501 output, 14.31818MHz

13
AMPLIFIER ADJUSTMENT
Idle Current
1. Rotate R5018 fully anti-clockwise.
2. Connect DC millivoltmeter to P5001.
3. Turn on the unit.
4. Adjust R5018 for 2mV +/- 0.2mV 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 P5001 R5018
FR P5101 R5118
C P5201 R5218
SL P5401 R5418
SR P5501 R5518
ISC Adjustment
A. Rotate R5634 fully clockwise.
B. Use 500mV, 1kHZ sine wave, EXT7.1 input, 8ohm loading to all channels.
C. Increase the output power of each channels to 80W(25.3V).
D. Note the THD readings should be larger than 0.2%.
E. Rotate R5624 anti-clockwise slowly until the THD readings is below 0.1%.
ADJUSTMENT POINT DIAGRAM
LEFT/RIGHT CHANNEL AMPLIFIER BOARD

14
PCB LAYOUT
POWER AMPLIFIER
FRONT AMP BOARD-COPPER SIDE

15
FRONT AMP BOARD-COMPONENT SIDE

16
SURROUND AMP BOARD-COPPER SIDE

17
SURROUND AMP BOARD-COMPONENT SIDE

18
DSP BOARD - COPPER SIDE

19
DSP BOARD - COMPONENT SIDE

20
KEY BOARD - COMPONENT SIDE KEY BOARD - COPPER SIDE