NAD C 425 User manual
NAD
C 425
STEREO
AM/FM TUNER
C 425
STEREO
AM/FM TUNER
SERVICE MANUAL
- 2 -
- 3 -
SERVICE SAFETY PRECAUTIONS
1. 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
REAR PANEL / FRONT PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
DISASSEMBLY INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ADJUSTMENT POINTS DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
INSTRUMENT SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
ALIGNMENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
PCB LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12
SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-14
IC BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-18
ELECTRICAL PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-27
EXPLODED VIEW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
EXPLODED VIEW PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-30
PACKING DIAGRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
- 2 -
- 3 -
SPECIFICATIONS
AM TUNER SECTION
Input level is expressed as the reading in open-circuit
of 75-ohm source impedance signal generator
Usable Sensitivity (999/1000kHz) ≤30dBµ
S/N Ratio (5mV in) ≥38dB
THD (5mV in) ≤3%
IF Rejection (450kHz) ≥36dB
Image Rejection (F+2xIF) ≥28dB
Selectivity ≥17dB
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 *AH
Input level is expressed as the reading in open-circuit
of 75-ohm source impedance signal generator
Usable Sensitivity (98 MHz) ≤13 dBµ ≤13 dBµ
Signal / Noise Ratio Mono ≥72 dB ≥72 dB
(60 dBµ, IHF wtd) Stereo ≥66 dB ≥66 dB
Frequency Response (20 Hz - 15 kHz, 60 dBµ) 0±1.0 dB 0±1.0 dB
Channel Separation (60 dBµ) 30 Hz ≥33 dB ≥33 dB
1 kHz ≥42 dB ≥42 dB
10 kHz ≥32 dB ≥32 dB
Alternate Channel Sensitivity
(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) ≥65 dB ≥65 dB
Image Rejection (119.4 MHz) ≥85 dB ≥85 dB
I.F. Rejection (10.7 MHz) ≥78 dB ≥78 dB
Pilot Suppression (60 dBµ) ≥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 ≤26 dBµ
PHYSICAL SPECIFICATIONS
Dimensions (Width x Height x Depth) 435 x 80 x 285 mm
Net weight 4 kg (8.8 lbs)
Shipping weight 5.1 kg (11.22 lbs)
- 4 -
- 5 -
REAR PANEL / FRONT PANEL
1. FM ANTENNA
2. AM ANTENNA
3. OUTPUT
4. IR IN
5. 12V TRIGGER IN
6. AC LINE CORD
7. RS-232
1. POWER ON / OFF
2. POWER STATUS INDICATOR
3. BLEND
4. MEMORY
5. FM MUTE / MODE
6. AM / FM
7. DISPLAY
8. PRESET / TUNE
9. DISPLAY AREA
10. PRESET / TUNE CONTROL
FRONT PANEL
REAR PANEL
IMPORTANT NOTES
1. Show the software version
Press “BLEND” and “AM/FM”.
2. Light UP all the icon on the VFD
Press “BLEND” & “DISPLAY”.
3. Factory test resets
When VFD all Light press any key.
4. AM Step 10K/9K Change
When AM band, press “AM/FM” & “PRESET/TUNE”.
5. Shipment resets
When pressing “DISPLAY” & “PRESET/TUNE” to VFD all Light, press any key.
- 4 -
- 5 -
5
4
3
1
2
7
6
6
DISASSEMBLY INSTRUCTIONS
1. Remove machine screws M 4.0 x 6.0 ( 1 to 4 ) from the side panels.
Remove tapping screw 3.0 x 8.5 5 from the back panel.
Refer to Figure No.1.
Figure No.1
2. Pull both sides of the TOP COVER slightly outwards 6 and tilt approx. 35˚ and then remove
in the direction as indicated by the arrow 7 . Refer to Figure No.2.
Figure No.2.
- 6 -
- 7 -
AM LOOP ANT FM ANT OUTPUT
FRONT END
ENV172D3G1
VFD
CPU
LC866448B
U201
U202
VFD DRIVER
PT6311
KEY MATRIX
Trigger IN
U203
EEPROM
24C08
PLL LC72723M
RDS DECODER
U901
AM/FM IF
LA1837
MUTING
IR IN
U701
74HC86
M218
REMOTE
SENSOR
POWER
SUPPLY
VFD
-VP
+5V CPU
+10V
AC INPUT
L
R
VT
VT
ce data clk RDS-CLK RDS-SIG RDS-DATA
MPXIN
data
out
(#1)=Power On
(#1)+(#2)=Standby
LC7218
U903
ST/MO, MUTE, SMETER
TUNE
FM
OSC/IF
AM
OSC/IF
1
27
17
16
23
2
30
U902
21
2 3 4 5 15
11
15
8
10 IN
16 14
20
16
14
22
12/13
5
16 19 24
19 18
BLOCK DIAGRAM
- 6 -
- 7 -
WIRING DIAGRAM
MAIN BOARD
KEY BOARD
DISPLAY BOARD
LED BOARD
TRANSFORMER
POWER SUPPLY BOARD
YELLOW
BLUE
WHITE
- 8 -
- 9 -
ADJUSTMENT POINTS DIAGRAM
OSC RF
VT
- 8 -
- 9 -
FM
SIGNAL
GENERATOR
ANTENNA
TERMINAL
OUTPUT
TERMINAL
DISTORTION
METER
DISTORTION
METER
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_J911
FM
SIGNAL
GENERATOR
AM
SIGNAL
GENERATOR
FM
SIGNAL
GENERATOR
RDS
GENERATOR
FM
STEREO
GENERATOR
P901
OUTPUT
TERMINAL
DC
MILLIVOLT-
METER
UNIT
UNIT
UNIT
UNIT
INSTRUMENT SETUP
1. FM MEASUREMENT
Fig. 1
Fig. 2
2. RDS MEASUREMENT
Fig. 3
3. AM MEASUREMENT
Fig. 4
- 10 -
ALIGNMENT PROCEDURES
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 47Kohm resistor unless otherwise noted.
Item Step Connection
of instrument FM SG
output
Stereo
modulator
output
Tuning
frequency Output
indicator Adjustment
point Adjust
for Remarks
FM
IF/RF
1
Fig.1
99.0MHz
1kHz 75kHz
devi.
65dBf (60dB)
– 99.0MHz
DC voltmeter L941 0±70mV FM MUTE/MODE
switch: ON/AUTO
Repeat the steps
1 to 3 until no
further adjustment
is necessary.
2 AC voltmeter IFT on the
front end Maximum
3Distortion
analyzer L942 Minimum
Stereo
Distortion Fig.2 99.0MHz Ext.
mod. 65dBf
(60dB)
Channel L
or R 1kHz 99.0MHz Distortion
analyzer IFT on the
front end Minimum
FM MUTE/MODE
switch: ON/AUTO
Don’t turn more
than ±180˚
Stereo
Separation Fig.2 99.0MHz Ext.
mod. 65dBf
(60dB)
Channel L
or R 1kHz 99.0MHz
Oscilloscope
R941
Maximum
separation
Repeat stereo
distortion and
stereo separation
alignment until
THD at minimum
and separation at
maximum.
Distortion
Meter Minimum
Mute
Level Fig.1 99.0MHz 18dB – 99.0MHz Oscilloscope R956 Signal
output
RDS Fig.3
99.0MHz Ext.
mod. 65dBf
(60dB)
RDS 2% MOD
– 99.0MHz – – – Decode
the RDS-
Program station
AM SECTION
AF Modulation: 400Hz, 30%
For AH Version
Step AM SG
output Tuning
frequency Output
indicator Adjustment
point Adjust
for
1 – 530kHz Digital
DC
voltmeter
OSC coil
on RF
block M971 1.35±0.2V
2600kHz
400Hz 30% mod.
60dB/m 600kHz AC
voltmeter
RF coil
on RF
block M971 Maximum
3600kHz
400Hz 30% mod.
60dB/m 990kHz AC
voltmeter L972 Maximum
For C Version
Step AM SG
output Tuning
frequency Output
indicator Adjustment
point Adjust
for
1 – 522kHz
or
531kHz
Digital
DC
voltmeter
OSC coil
on RF
block M971
1.3±0.2V (522kHz)
1.35±0.2V
(531kHz)
2600kHz
400Hz 30% mod.
60dB/m 603kHz AC
voltmeter
RF coil
on RF
block M971 Maximum
3600kHz
400Hz 30% mod.
60dB/m 999kHz AC
voltmeter L972 Maximum
- 11 -
PCB LAYOUT
POWER SUPPLY BOARD
DISPLAY BOARD
LED BOARD KEY BOARD
- 12 -
- 13 -
MAIN BOARD
- 12 -
- 13 -
SCHEMATIC DIAGRAM
KEY / MCU / DISPLAY
NOTE: 1. RESISTORS ARE CARBON FILM 5% 1/8W
UNLESS OTHERWISE SPECIFIED.
2. CERAMIC CAPACITORS ARE 50V 10%
UNLESS OTHERWISE SPECIFIED.
425KB-MP.sch-1 - Tue Jul 18 09:17:14 2006
6.5V
- 14 -
TUNER
NOTE: 1. RESISTORS ARE CARBON FILM 5% 1/8W
UNLESS OTHERWISE SPECIFIED.
2. CERAMIC CAPACITORS ARE 50V 10%
UNLESS OTHERWISE SPECIFIED.
- 15 -
Serial
Data
Interface
DIN
DOUT
CLK
STB
VDD
R
OSC
SW1
SW2
SW3
SW4
LED1
LED2
LED3
LED4
LED5
K1 K2 K3 K4 VDD GND VEE
SG1/KS1
OSC
General
Input
Register
LED
Driver
Dimming Circuit
Grid
Driver
Segment
Driver
Grid
Driver
Key Scan
Output
Control
Dispaly Memory
Timing Generator
Key Matrix Memory
SG2/KS2
SG3/KS3
SG4/KS4
SG5/KS5
SG6/KS6
SG7/KS7
SG8/KS8
SG9/KS9
SG10/KS10
SG11/KS11
SG12/KS12
SG13/GR16
SG14/GR15
SG15/GR14
SG16/GR13
SG17/GR12
SG18/GR11
SG19/GR10
SG20/GR9
GR1
GR2
GR3
GR4
GR5
GR6
GR7
GR8
IC BLOCK DIAGRAM
Display Board
U202: PT6311
- 16 -
- 17 -
Main Board
U201: P89LCP936
ACCELERATED 2-CLOCK 80C51 CPU
4 kb/8 kB/16 kB
CODE FLASH
256-BYTE
DATA RAM
PORT 2
CONFIGURABLE I/Os
PORT 1
CONFIGURABLE I/Os
PORT 0
CONFIGURABLE I/Os
KEYPAD
INTERRUPT
PROGRAMMABLE
OSCILLATOR DIVIDER
CPU
clock
CONFIGURABLE
OSCILLATOR
ON-CHIP
RC
OSCILLATOR
internal bus
CRYSTAL
OR
RESONATOR
POWER MONITOR
(POWER-ON RESET,
BROWNOUT RESET)
UART
ANALOG
COMPARATORS
512-BYTE
AUXILIARY RAM
I2C-BUS
512-BYTE
DATA EEPROM
(P89LPC935/936)
PORT 3
CONFIGURABLE I/Os
CCU (CAPTURE/
COMPARE UNIT)
(P89LPC935/936)
P89LPC933/934/935/936
WATCHDOG TIMER
AND OSCILLATOR
TIMER 0
TIMER 1
REAL-TIME CLOCK/
SYSTEM TIMER
SPI
ADC1/DAC1
ADC0/DAC0
(P89LPC935/936)
P3[1:0]
P2[7:0]
P1[7:0]
P0[7:0]
X2
X1
TXD
RXD
SCL
SDA
T0
T1
CMP2
CIN2B
CIN2A
CMP1
CIN1A
CIN1B
OCA
OCB
OCC
OCD
ICA
AD10
AD11
AD12
AD13
DAC1
AD00
AD01
AD02
AD03
DAC1
ICB
SPICL
K
MOSI
MISO
SS
P89LPC935FDH
P89LPC936FDH
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
15
18
17
20
19
22
21
24
23
26
25
28
27
P2.0/ICB/DAC0/AD03
P2.1/OCD/AD02
P0.0/CMP2/KBI0/AD01
P1.7/OCC/AD00
P1.6/OCB
P1.5/RST
VSS
P3.1/XTAL1
P3.0/XTAL2/CLKOUT
P1.4/INT1
P1.3/INT0/SDA
P1.2/T0/SCL
P2.2/MOSI
P2.3/MISO
P2.7/ICA
P2.6/OCA
P0.1/CIN2B/KBI1/AD10
P0.2/CIN2A/KBI2/AD11
P0.3/CIN1B/KBI3/AD12
P0.4/CIN1A/KBI4/DAC1/AD13
P0.5/CMPREF/KBI5
VDD
P0.6/CMP1/KBI6
P0.7/T1/KBI7
P1.0/TXD
P1.1/RXD
P2.5/SPICLK
P2.4/SS
- 16 -
- 17 -
VCC 8
7
4
6
5
3
2
1
GND
WP
SCL
LOAD
LOAD INC
DATA WORD
ADDR/COUNTER
Y DEC
X DEC
R/W
COMP
SERIAL
CONTROL
LOGIC
EN H.V. PUMP/TIMING
DATA RECOVERY
EEPROM
SERIAL MUX
DOUT/ACK
LOGIC
DEVICE
ADDRESS
COMPARATOR
START
STOP
LOGIC
SDA
A2
A1
A0
DIN
DOUT
Main Board
U203: AT24C08A-10PU
Main Board
U204: MAX232D
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
V
CC
GND
T1OUT
R1IN
C2+
C1-
V+
C1+
R1OUT
T1IN
T2IN
R2OUT
R2IN
T2OUT
V-
C2-
Main Board
U402: NJM78M56FA
1
INPUT
3
OUTPUT
2
GND
Main Board
U701: 74HC86
1
2
3
4
5
6
7
14
13
12
11
10
9
8
1A
1B
1Y
2A
2B
2Y
GND
VCC
4B
4A
4Y
3B
3A
3Y
12345678910 11 12 13 14 15
30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
ALC AM
OSC
AM
MIX
AM
RF.AMP
REG
AGC
AM IF
AM
S-METER
TUNING
DRIVE
STEREO
DRIVE
VCC
VCC
AM/FM
IF-BUFF
FM
S-METER S-CURVE
AM IF FM
DET
GND
FM IF INPUT
AM MIXER
OUTPUT
FM IF INPUT
BYPASS
AM IF INPUT
GND
TU-LED
ST LED
AM-IF OUTPUT
FM DETECTOR
A
M NARROW CF
FM S-METER
OUTPUT
AM S-METER
OUTPUT
MUTE
FM/AM
SWITCH
PILOT VCO
SD
COMP
DET
BUFF
DECODER
ANTI-BIRIDE
3 rd 5 th
STEREO
SW
MUTE
VCO
304kHz
FF
38k
P-DET
Ø
FM SD
ADJ
OSC
REG
AM RF
INPUT
AFC
AM AGC
AM DETECTOR
INPUT
FM DETECTOR
OUTPUT
MPX
IUTPUT
MPX
OUTPUT
MPX
OUTPUT
AM STEREO L
INPUT
AM STEREO R
INPUT
L-OUT
R-OUT
FF
19k
FF
19k
PILOT
DET
Main Board
U901: LA1837L-E
- 18 -
- 19 -
Main Board
U902: LC72723M
Vdda
3
REFERENCE
VOLTAGE
ANTIALIASING
FILTER
DATA
DECODER
VREF
1
VREF
FLOUT
5
CIN
6
PLL
(57kHz)
CLOCK
RECOVERY
(1187.5Hz)
+
_
Vddd
11
Vssd
10
RDDA
14
RDCL
15
MODE
12
RST
13
RDS-ID/READY
16
Vssa
4
MPXIN
2
TEST
7TEST
57kHz
BPF
(SCF) SMOOTHING
FILTER
OSC
CLK(4.332MHz)
9
XIN
8
XOUT
RDS-ID
DETECT
RAM
(128bits)
21
22
16
15
20
23
871714131211109
5
4
3
2
18
19
24
1
6
XIN
FMIN
AMIN
CE
DI
CL
D0
OUT0 OUT1
XOUT
PHASE DETECTOR
CHARGE PUMP
REFERENCE
DIVIDER
SWALLOW COUNTER
1/16, 1/17 4 BIT
SHIFT REGISTER
LATCH
UNIVERSAL
COUNTER
1
2
12-BIT PROGRAMMABLE
DIVIDER
SYC
OUT2 OUT3 OUT4 OUT5 OUT6 IN0 IN1
VSS
VDD
LCTR
HCTR
PD2
PD1
Main Board
U903: LC7218-E
- 18 -
- 19 -
ELECTRICAL PARTS LIST
DISPLAY ASSY
PC BOARD
PCB-C42526+DSP PCB ASSY DISPLAY
PCB
1725-859A+0000 PCB MAIN/KEY/DIS/PSU/LED
CAPACITOR
C201 157B-107M+K-LII CE 6.3V 100UF 20% RLT
C202 150F-103K+2-FC CC 50V 0.01uF 10% AT 3.5
C210 150F-104K+2-FC CC 50V 0.1UF 10% AT
C211 157Q-107M+K-LUI CE 35V 100UF 20% RLT
C212 157B-107M+K-LII CE 6.3V 100UF 20% RLT
C213 150F-104K+2-FC CC 50V 0.1UF 10% AT
DIODE
D201, D206 4804-1480+C DIODE 1N4148M-A(WA) ATS
WAFER/CONNECTOR
J202A 2101-1441+0 FLEXIBLE CONN 15P P1.0 R
J203A 2102-031R+004 WAFER 3P P2.5 RIGHT
TRANSISTOR
Q201, Q202 485C-114E+K TR DTC114ES RLT
RESISTOR
R210, R211 4701-221J+2 RCF 1/8W 220R 5% AT
R215, R216 4701-471J+2 RCF 1/8W 470R 5% AT
R219 4701-681J+2 RCF 1/8W 680R 5% AT
R220 4701-821J+2 RCF 1/8W 820R 5% AT
R221 4701-182J+2 RCF 1/8W 1.8K 5% AT
R222 4701-681J+2 RCF 1/8W 680R 5% AT
R227 4701-563J+2 RCF 1/8W 56K 5% AT
IC
U202 3131-8700+0 IC PT6311(L) VFD DRIVER
SWITCH
M201, M202, M203, M204, M205, M206 5200-3538+0 SWITCH, TACT SKHHBY 7MM
Location Part Number Description
- 20 -
- 21 -
Location Part Number Description
WIRE
J201A 7012-6688+0 CONN WIRE 3P P=2.5 26AWG
MISCELLANEOUS
M209 4154-2101+0 VFD HOLDER
M210 4814-3TE2+3 IR SENSOR PIC-26043TE2
VFD 2460-1961+0 DISPLAY-VFD HNA-10SM55
KEY ASSY
PC BOARD
PCB-C42526+KEY PCB ASSY KEY C425
PCB
1725-859A+0000 PCB MAIN/KEY/DIS/PSU/LED
CAPACITOR
C230, C231 150F-103K+2-FC CC 50V 0.01uF 10% AT 3.5
WAFER
J201B 2102-031R+004 WAFER 3P P2.5 RIGHT
MISCELLANEOUS
VR201 5200-4951+0 ENCODER ROTARY DPDT
LED ASSY
PC BOARD
PCB-C42526+LED PCB ASSY LED
PCB
1725-859A+0000 PCB MAIN/KEY/DIS/PSU/LED
LED
D209 3700-3517+RG LED RED/GREEN (L-469HGW)
WIRE
J203B 7012-6688+0 CONN WIRE 3P P=2.5 26AWG
MAIN ASSY
PC BOARD
*EU PCB-C42526+MAIN PCB ASSY MAIN
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