NAD T-973 Schematic

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T 973

Seven Channel Amplifier

PRELIMINARY SCHEMATICS updated alignment procedures

ISSUE DATE: September 2005

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.

heat the unit for 10 to 15 minutes, and then readjust to 8mV +/- 2mV.

Pre

(Please note:

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.

The idling current must be adjusted when all modules are assembled into the

T 973 WIRING DIAGRAM

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MOLEX 2145/3215 TOP ENTRY/9PIN

MOLEX 52207 RIGHT ANGLE/SMT/ZIF/TOP CONTACT STYLE/16PIN

SCHEMATIC DIAGRAM(AMP CONNECTION)

FAN1 DGND

FAN2 DGND

15

16

STBY

15

16

STBY

SEN2

SEN3

SEN1

SEN7

P604B

P611B

COPPER STRIP

11223344556677889

9

AGND4A

+62V_4A

-62V_4A

AGND4B

-62V_4B

AGND4

-62V_4

+62V_4A

MOLEX 2145/3215 TOP ENTRY/9PIN

11223344556677889

+62V_4B

11223344556677889

+62V_4

MOLEX 2145/3215 TOP ENTRY/9PIN

11223344556677889

ISCTRIG_1 ISCTRIG_3 ISCTRIG_5 ISCTRIG_6 ISCTRIG_7

AGND4A

P621B

HEADER 2

P621B

1 2

HEADER 2

P622

HEADER 2

P622

HEADER 2

1 2

9

AGND4B

ISCTRIG_2

AGND4B

MOLEX 2145/3215 TOP ENTRY/9PIN

P613B

9

AGND4

9

P612B

P614B

+62V_4A

+62V_4B

+62V_4

-62V_4A

-62V_4B

-62V_4

AGND4A

AGND4B

AGND4

COPPER STRIP

BUS601

COPPER STRIP

BUS602

COPPER STRIP

BUS603

P604B

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9

MOLEX 2145/3215 TOP ENTRY/9PIN

-68V

ACOFF

+68V

PROT1

SEN1

9

-68V

ACOFF

+68V

PROT2

SEN2

MOLEX 2145/3215 TOP ENTRY/9PIN

P606B

9

-68V

ACOFF

+68V

PROT3

SEN3

9

MOLEX 2145/3215 TOP ENTRY/9PIN

SCN_4

+18V

-18V

SCP_4

P605B

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SCN_4

+18V

-18V

SCP_4

11223344556677889

SCN_4

+18V

-18V

SCP_4

MOLEX 2145/3215 TOP ENTRY/9PIN

P607B

11223344556677889

PROT3

+8V

PROT4

+8V

SEN5

SEN4

101214

AGND

SEN6

101214

8

DGND

SCLED

PROT1

PROT2

AGND

135791113

P601B

246

8

PROT6

DGND

SCLED

PROT7

PROT5

MOLEX 52207 RIGHT ANGLE/SMT/ZIF/TOP CONTACT STYLE/16PIN

ISCTRIG_6

ISCTRIG_2

DGND

ISCTRIG_4

135791113

P602B

246

ISCTRIG_7

ISCTRIG_5

ISCTRIG_3

ISCTRIG_1

FAN3 DGND

1 2

P623

HEADER 2

P623

HEADER 2

1 2

AGND4

ISCTRIG_4

MOLEX 5145-NCH TOP ENTRY/8PIN

P619B

8

AGND4

8

AGND6

MOLEX 2145/3215 TOP ENTRY/9PIN

AGND4

AGND6

+62V_4

112233445566778

-62V_4

+62V_4

-62V_4

MOLEX 5145-NCH TOP ENTRY/8PIN

P620B

112233445566778

+62V_3

-62V_3

+62V_3

-62V_3

+62V_4

-62V_4

AGND4

P615B

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9

+62V_3

-62V_3

AGND6

9

AGND6A

MOLEX 2145/3215 TOP ENTRY/9PIN

AGND6

AGND6A

-62V_3A

+62V_3

MOLEX 2145/3215 TOP ENTRY/9PIN

P616B

11223344556677889

+62V_3A

+62V_3

+62V_3A

+62V_3B

-62V_3

-62V_3A

-62V_3B

ACOFF

SEN4

MOLEX 51021/12PIN/500mm WIRE

101112

SCP_4

+62V_3

-62V_3

-62V_4

+62V_4

COPPER STRIP

BUS604

9

ACOFF

SEN5

MOLEX 2145/3215 TOP ENTRY/9PIN

P609B

COPPER STRIP

BUS605

9

ACOFF

SEN6

-68V

PROT4

SCN_4

SCP_3

-68V

PROT5

-18V

+68V

SCLED

SCN_3

-18V

+68V

SCN_4

+18V

SCP_4

S10B-PH-SM3-TB

P603B

10

9

P618B

123456789

+8V

DGND

STBY

MOLEX 2145/3215 TOP ENTRY/9PIN

11223344556677889

SCN_3

+18V

SCP_3

11223344556677889

P608B

AGND

FAN1

FAN2

FAN3

-68V

+68V

ACOFF

+18V

-18V

11223344556677889

-68V

PROT6

-18V

+68V

SCN_3

+18V

SCP_3

MOLEX 2145/3215 TOP ENTRY/9PIN

DGND

P617B

9

AGND6B

-62V_3B

AGND6B

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+62V_3B

-62V_3B

+62V_3B

AGND6

AGND6A

AGND6B

COPPER STRIP

BUS606

9

ACOFF

SEN7

-68V

PROT7

-18V

+68V

+18V

SCP_3

11223344556677889

SCN_3

P610B

NAD T-973 Schematic

Specifications and Main Features

Frequently Asked Questions

User Manual