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

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 Only for v1.08 or higher.
Check MCU Version Source Down + Source UP For v1.03 or higher, this checks all versions.
Check DSP Version Source Down + Listening Mode Only for v1.02 or older.
Check Current Video Mode Source Down + Tone Controls
MIC Test Source Down + Tone Defeat
VFD Test Source Down + Display
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

12
DETAILS & WAVEFORMS ON SYSTEM TEST & DEBUGGING
DSP
U1007 Pin 70 - Clock for external memory,
100MHz
U1007 Pin 17 - X1001C output, 24.576MHz
U1007 Pin 2 - Master clock (Analog), 12.288MHz U1007 Pin 2 - Master clock (PCM), 11.2896MHz
U1007 Pin 12 – Left/Right clock (Analog), 48kHz U1007 Pin 12 - Left/Right clock (PCM), 44.1kHz

13
U1007 Pin 9 - Serial clock (Analog), 3.072MHz
MCU
U2001 Pin 12 - X2001A output, 20.000MHz
HDMI
U12 Pin 38 – U3 output, 28.636MHz

14
U9 Pin 1 –DAC_HS (OSD Off), 31.48kHz U9 Pin 54 –DAC_VS (OSD On, NTSC), 60Hz
U9 Pin 1 –DAC_HS (OSD On), 15.72kHz U9 Pin 54 –DAC_VS (OSD On, PAL), 50Hz
U9 Pin 54 –DAC_VS (OSD Off), 60Hz U9 Pin 4 –DAC_FLD (OSD Off), Idle

15
U9 Pin 4 –DAC_FLD (OSD On, NTSC), 30Hz U9 Pin 51 –PCLK (OSD On), 27MHz
U9 Pin 4 –DAC_FLD (OSD On, PAL), 25Hz
U9 Pin 51 –PCLK (OSD Off), 27MHz

16
ADJUSTMENT POINT DIAGRAM
LEFT CHANNEL AMPLIFIER BOARD
RIGHT CHANNEL AMPLIFIER BOARD
ISC-L BOARD

17
AMPLIFIER ADJUSTMENT
Idle Current
1. Rotate R5221 fully clockwise.
2. Connect DC millivoltmeter to P5501 (i.e. Across half of R5228 and R5530, 0.22 Ohm resistor).
3. Turn on the unit.
4. Adjust R5221 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 P5501 R5521
FR P5001 R5021
C P5101 R5121
SL P5601 R5621
SR P5201 R5221
BS P5701 R5721
BSR P5301 R5321
ISC adjustment
A. Rotate R8203 fully clockwise
B. Use 500mV, 1kHz sine wave, EXT 7.1 input, 8 loading to all channels
C. Increase the output power of FL/SL/BSL channels to 120W (31V)
D. Note the THD readings should be larger than 0.2%
E. Rotate R8203 anti-clockwise slowly until the THD reading is below 0.1%
F. Repeat for R8303 using FR/SR/BSR/C channels.
ISC-R BOARD

18
PCB LAYOUT
POWER AMPLIFIER
LEFT_CH BOARD-COPPER SIDE

19
LEFT_CH BOARD - COMPONENT SIDE

20
RIGHT_CH BOARD-COPPER SIDE