NAD T785 User manual

NAD
SERVICE MANUAL
T 785
T 785
Surround Sound
Receiver
Surround Sound Receiver
DRAFT DATE: MARCH 2010

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.
9

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 20-001-0078-90 FUSE TIME-LAG 10A/250VAC 5X20mm
UL/CSA 5T
F8001*C,CT 20-001-0078-90 FUSE TIME-LAG 10A/250VAC 5X20mm
UL/CSA 5T
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)
Before returning the product to the customer, make leakage current or resistance measurements to determine
that exposed parts are acceptably insulated from supply circuit.
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................................................12-15
ADJUSTMENT POINTS DIAGRAM / AMPLIFIER ADJUSTMENT..................................................16-17
PCB LAYOUT...................................................................................................................................18-41
SCHEMATIC DIAGRAM...................................................................................................................42-69
ELECTRICAL PARTS LIST..............................................................................................................70-95
IC BLOCK DIAGRAM.....................................................................................................................96-120
EXPLODED VIEW........................................................................................................................121-122
EXPLODED VIEW PARTS LIST ..................................................................................................123-126
SINGLE CHANNEL SERVICE KIT ..............................................................................................127-128
PACKING DIAGRAM...........................................................................................................................129

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) 1.46 ±0.1 V
S/N Ratio (A-wtd, 1kHz, 1 W, 8 ohm, SL/SR/BL) ≥- 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, 10 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 Response
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 180 x 431 mm
Net Weight 26.05 Kg (57.31 lbs)
Shipping Weight 31.1 Kg (68.42 lbs)

6
FRONT PANEL
REAR PANEL / FRONT PANEL VIEW
REAR PANEL
1. DIGITAL AUDIO IN/OUT
2. FM,AM ANTENNA INPUT
3. COMPONENT IN/OUT
4. MP DOCK
5. AUDIO/VIDEO 3/4 OUT
6. MONITOR(S-VIDEO,VIDEO)
1. POWER BUTTON
2. STANDBY LED
3. INFO
4. AM/FM/DB
5. TUNER MODE
6. MEMORY
7. NAVIGATION AND
ENTER BUTTON
8. VACUUM, FLUORES
CENT DISPLAY(VFD)
9. VOLUME
10. SPEAKER A/B
11. SOURCE
12. LISTENING MODE
13. TONE CONTROLS
14. TONE DEFEAT
15. FRONT INPUT/MP
16. PHONES
17. FRONT INPUT JACKS
18. MP/MIC INPUT
7. AUDIO/VIDEO 1~6 IN
8. 7.1 CH INPUT
9. XM MODULE INPUT(AH)
DAB MODULE INOUT(C,CT)
10. RS-232
11. SOFT CLIPPING
12. +12V TRIGGER OUT
13. IR IN/OUT
14. HDMI
15. ZONE 2,3,4
16. AUDIO PREOUT
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 (x8 pcs) from the side panels.
Remove tapping screw 3.5 x 8.0 (x4 pcs) 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 17-012-2965-90 CABLE ASSY 4 WAYS #26 2.5P L=400mm (RoHS) PSU BD-J8002A
2 17-012-3943-90 CABLE ASSY 1 WAY #16 UL1672 BLUE L=140mm PSU BD-J8011
FASTON 4.8mm (RoHS)
3 17-012-3944-90 CABLE ASSY 1 WAY #16 UL1672 BROWN L=140mm PSU BD-J8012
FASTON 4.8mm (RoHS)
4 17-012-3940-90 CABLE ASSY 3 WAYS #26 2.5P UL2854 L=110 (ROHS) VOL BD-
J6004A/B
5 17-012-3938-90 CABLE ASSY 1 WAY #18 UL1007 L=320MM DSP BD-J1002A
W/ HEADER (RoHS)
6 17-012-3378-90 CABLE ASSY 20 WAYS #28 UL2651 L=240mm KEYBOARD-
PCB MOUNT (RoHS) J2002B
7 17-012-3173-90 CABLE ASSY 14 WAYS #26 2.5P UL1533 L=100 (RoHS) PRE-OUT BD-
J5404B
8 17-012-3176-90 CABLE ASSY 3 WAYS #18 3.96P UL1007 L=80 (RoHS) SEC BD-J5402B
9 17-012-3603-90 CABLE ASSY 2 WAYS #18 UL1007 L=170MM (RoHS) SEC BD-
J8105A,J8106A
10 17-012-3604-90 CABLE ASSY 6 WAYS #18 UL1007 L=140MM (RoHS) SEC BD-J8104A
11 17-012-3174-90 CABLE ASSY 5 WAYS #18 3.96P UL1007 L=300mm SPK BD-
(W/R/B/V/O) (RoHS) J5403B1-B5
12 17-012-3947-90 CABLE ASSY 4 WAYS #18 3.96P UL1007 L=260 SPK BD-
(W/R/Y/BL) (RoHS) J5802B1-B4
13 17-012-3329-90 CABLE ASSY 3 WAYS #18 UL1007 3.96P L=420 (RoHS) SPK BD-
J8106B1-B3
14 17-012-3330-90 CABLE ASSY 4 WAYS #18 UL1007 3.96P L=440 (RoHS) SPK BD-
J8105B1-B4
15 17-012-3171-90 CABLE ASSY 6 WAYS #26 2.5P UL1533 L=200 (RoHS) V6 VD-J2006B
16 17-012-3404-90 CABLE ASSY 6 WAYS #26 2.5P UL1007 L=150 (RoHS) V6 BD-J2005B
17 17-012-3939-90 CABLE ASSY 3 WAYS #26 2.5P UL2468 L=180 (RoHS) ISC-L BD-
J5803B,
ISC-R BD-
J5810B
18 17-012-3930-90 CABLE ASSY 4 WAYS #26 2.5P UL1533 L=160 (RoHS) V6 BD-J2008A
19 17-012-3936-90 CABLE ASSY 3 WAYS #26 2.5P UL2854 L=310 (RoHS) CONN#1-J9006A
20 17-012-3937-90 CABLE ASSY 5 WAYS #26 2.5P UL2854/1533 CONN#1-
L=230/320 (RoHS) J9004A/J9005A
21 17-012-3938-90 CABLE ASSY 1 WAY #18 UL1007 L=320 W/ HEADER CONN#1-
(RoHS) JP9001A
22 17-012-3941-90 CABLE ASSY 3 WAYS #26 2.5P UL2854 L=130 (RoHS) CONN#1-
J9008A/B
23 17-012-3457-90 CABLE ASSY 8 WAYS #26 UL1007 2.5P L=120 (RoHS) CONN#2-J8202B
24 17-012-3458-90 CABLE ASSY 10 WAYS #26 UL1007 2.5P L=80 (RoHS) CONN#2-J8201B
25 17-010-0124-90 FFC CABLE 17 PINS P1.25 L=180 15 & 16 PINS VOID TUNER-J5404B
(RoHS)
26 17-012-2874-90 CABLE ASSY 1 WAY #16 UL1672 BLUE L=100mm J8015,J8017
(RoHS)
27 17-012-2875-90 CABLE ASSY 1 WAY #16 UL 1015 GREEN/YELLOW CHASSIS GND,
L=100 (RoHS) AC OUTLET
GND
28 17-012-3166-90 CABLE ASSY 20 WAYS #28 UL2651 L=100mm (RoHS) J2001C
29 17-012-3298-90 CABLE ASSY 3 WAYS #18 UL1007 L=420mm (RoHS) J5402A/B
30 17-012-3346-90 CABLE ASSY 26 WAYS #28 UL2651 L=330mm (RoHS) J2301C
31 17-012-3942-90 CABLE ASSY 26 WAYS #28 UL2651 L=230mm (RoHS) J2007C
32 17-012-3948-90 CABLE ASSY 1 WAY #16 UL1672 BROWN L=100 J8013,J8016
(RoHS)
33 17-012-3963-90 CABLE ASSY 1 WAY #18 UL1007 L=200 W/ HEADER TUNER-J6102A
(RoHS)
34 17-012-4020-90 CABLE ASSY 3 WAYS #26 2.5P UL2547 L=300 (RoHS) TUNER-J9501A
35 17-012-4021-90 CABLE ASSY 1 WAY AWG18 UL1007 BLACK L=200mm MAIN-JP7006B-
W/INT. TEETH RING TERMINAL (RoHS) GND,
SEC BD-GND
36 17-012-3605-90 CABLE ASSY 6 WAYS #18 UL1007 L=170MM SEC BD-J8103A
37 17-012-3573-90 CABLE ASSY 20 WAYS #28 UL2651 L=130mm (RoHS) J7001C

10
BLOCK DIAGRAM