NAD T973 Service Manual

Cover page of NAD T973 Service Manual

Service Manual for NAD T973, downloadable as a PDF file.

We also have owner's manual to this model.

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Pr
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ISSUE DATE: September 2005
T 973
Seven Channel Amplifier
PRELIMINARY SCHEMATICS updated alignment procedures
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Pr
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ISSUE DATE: September 2005
T 973
Seven Channel Amplifier
PRELIMINARY SCHEMATICS updated alignment procedures
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ALIGNMENT PROCEDURE (T973)
A. DC OFFSET VOLTAGE
The DC OFFSET between OFFSET Test Point and AGND must be controlled within
0+/-3mV. If it's found to be out of this range, change the TL084BCD to get it meet the
requirement.
B. IDLING CURRENT
The idling current at the final stage of the unit should be set to about 40mA+/-10mA.
Adjust RV102 (As marked as "Idling Current ADJ" in the enclosed drawing below) to
control the voltage between Idling current Test point 1 and 2 to be 8mV +/- 2mV.
Preheat the unit for 10 to 15 minutes, and then readjust to 8mV +/- 2mV.
(Please note: The idling current must be adjusted when all modules are assembled into the
unit.)
C. ISC SENSITIVITY
Adjust Pot RV104 (as marked as "ISC SENS ADJ" in the below drawing) to get the voltage
across "ISC SENS TEST POINT" and AGND to be 0mV+/-10mV.
(Please note that the ISC should be adjusted when all modules are assembled into the unit. It's
not possible to get 0V +/-10mV if the modules are not assembled.
D. THERMAL SENSE ADJUSTMENT
The adjustment should be always done when the T973 is cool condition. (That means the
temperature inside the unit should be almost same as the ambient temperature.
Connector P208B that connects the transformer and power board should be removed to
avoid that the Idling current to heat up the unit excessively)
At ambient temperature of 25 C degree and when the unit is just turned on (still in cool
condition), adjust the pot RV103 (as marked as "THERMAL SENS ADJ" in the below
drawing) to get voltage across the THERMAL TEST POINT and AGND to be 750mV
+/-10mV. While the ambient temperature is different, the voltage will vary as well. There
is a relation between the temperature and voltage, that is; if the ambient temperature is 20
degree C, the voltage should be 850mV+/-10mV; if the ambient temperature is 30 degree
C, the voltage should be adjusted to 650mV+/-10mV, etc.
E. Fan Cut Off Point Adjustment
Note: This Fan cut off function does not appear on PCB V10.0, V11.0 or MKII version but
only appeared on PCB V12.0. Run the unit for all 7 channels at 1 kHz, 4ohms load, and
250mW output. Do this adjustment when the unit heats up, for example; run the unit at
all 7 channels at 50W/4ohms for 10 minutes. Then adjust Pot RV201 on power supply
board so the voltage at Pin14 of IC203 just changes from negative to positive (to get the
fans just start turning). Then turn off the input signal and monitor if fans will stop within 30
seconds, then turn on the input signal again to see if the fans start turning immediately.
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T 973 WIRING DIAGRAM
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Preli
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AGND4
-62V_4
+62V_4
AGND4
+62V_4
AGND4
-62V_4
AGND4
PROT6
DGND
STBY
DGND
PROT3
SCLED
PROT4
PROT7
SCLED
PROT5
+8V
PROT1
PROT2
STBY
AGND
+8V
-68V +68V
DGND
AGND
ACOFF +18V
FAN2
-18V
FAN3
FAN1
+8V
AGND6
+62V_3
AGND6
-62V_3
AGND6
+62V_3
DGND
SCLED
SCN_3
SCN_4
SCP_4
+62V_3
SCP_3
-62V_3
-62V_4 +62V_4
-68V
SCN_3
+18V
ACOFF
-18V
+68V
PROT5
SEN5
SCP_3
-68V
SCN_3
+18V
ACOFF
-18V
+68V
PROT6
SEN6
SCP_3
-68V
SCN_3
+18V
ACOFF
-18V
+68V
PROT7
SEN7
SCP_3
AGND6B
+62V_3B
-62V_3B
-62V_3B
AGND6B
+62V_3B
AGND6A
+62V_3A
-62V_3A
-62V_3A
AGND6A
AGND6A
+62V_3A
+62V_3
-62V_3
-62V_3
AGND6
AGND6
+62V_3
-68V
SCN_4
+18V
ACOFF
-18V
+68V
PROT1
SEN1
SCP_4
AGND4A
+62V_4A +62V_4A
-68V
SCN_4
+18V
ACOFF
-18V
+68V
PROT2
SEN2
SCP_4
AGND4B
+62V_4B
-62V_4B
AGND4B
-68V
SCN_4
+18V
ACOFF
-18V
+68V
PROT3
SEN3
SCP_4
AGND4
+62V_4
-62V_4
-62V_4
AGND4
+62V_4
+62V_4
-62V_4
-62V_4
AGND4
AGND4
+62V_4
-68V
SCN_4
+18V
ACOFF
-18V
+68V
PROT4
SEN4
SCP_4
STBY
AGND
SEN2 SEN3
SEN5
ISCTRIG_6
ISCTRIG_7
SEN1
ISCTRIG_5
ISCTRIG_3
ISCTRIG_2
AGND6B
AGND6
FAN1
DGND
DGND
FAN2
DGND
FAN3
+62V_3
+62V_3B
+62V_3A
-62V_3
-62V_3B
-62V_3A
AGND6
AGND6B
AGND6A
ISCTRIG_1
ISCTRIG_3
ISCTRIG_5
ISCTRIG_6
ISCTRIG_7
ISCTRIG_1
SEN6
SEN7
DGND
ISCTRIG_4
SEN4
AGND4A AGND4A
-62V_4A -62V_4A
ISCTRIG_2 AGND4B
-62V_4B
+62V_4B
AGND4
ISCTRIG_4
AGND4
-62V_3
AGND6
AGND4A
AGND4B
AGND4
-62V_4A
-62V_4B
-62V_4
+62V_4A
+62V_4B
+62V_4
SCHEMATIC
DIAGRAM(AMP
CONNECTION)
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
P603B
S10B-PH-SM3-TB
P603B
S10B-PH-SM3-TB
1
1
2
2
P622
HEADER
2
P622
HEADER
2
BUS606
COPPER
STRIP
BUS606
COPPER
STRIP
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P608B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P608B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
P623
HEADER
2
P623
HEADER
2
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P615B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P615B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
2
3
4
5
6
7
8
9
10
11
12
P618B
MOLEX
51021/12PIN/500mm
WIRE
P618B
MOLEX
51021/12PIN/500mm
WIRE
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P609B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P609B
MOLEX
2145/3215
TOP
ENTRY/9PIN
BUS603
COPPER
STRIP
BUS603
COPPER
STRIP
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P616B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P616B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P610B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P610B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
3
5
7
9
11
13
15
2
4
6
8
10
12
14
16
P601B
MOLEX
52207
RIGHT
ANGLE/SMT/ZIF/TOP
CONTACT
STYLE/16PIN
P601B
MOLEX
52207
RIGHT
ANGLE/SMT/ZIF/TOP
CONTACT
STYLE/16PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P604B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P604B
MOLEX
2145/3215
TOP
ENTRY/9PIN
BUS601
COPPER
STRIP
BUS601
COPPER
STRIP
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
P619B
MOLEX
5145-NCH
TOP
ENTRY/8PIN
P619B
MOLEX
5145-NCH
TOP
ENTRY/8PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P617B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P617B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P611B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P611B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P605B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P605B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P612B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P612B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P606B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P606B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
3
5
7
9
11
13
15
2
4
6
8
10
12
14
16
P602B
MOLEX
52207
RIGHT
ANGLE/SMT/ZIF/TOP
CONTACT
STYLE/16PIN
P602B
MOLEX
52207
RIGHT
ANGLE/SMT/ZIF/TOP
CONTACT
STYLE/16PIN
BUS602
COPPER
STRIP
BUS602
COPPER
STRIP
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P613B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P613B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P607B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P607B
MOLEX
2145/3215
TOP
ENTRY/9PIN
BUS604
COPPER
STRIP
BUS604
COPPER
STRIP
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
P614B
MOLEX
2145/3215
TOP
ENTRY/9PIN
P614B
MOLEX
2145/3215
TOP
ENTRY/9PIN
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
P620B
MOLEX
5145-NCH
TOP
ENTRY/8PIN
P620B
MOLEX
5145-NCH
TOP
ENTRY/8PIN
1
1
2
2
P621B
HEADER
2
P621B
HEADER
2
BUS605
COPPER
STRIP
BUS605
COPPER
STRIP

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