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Technical Bulletin T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-01
Date:
Note:
Previous T.B.’s required:
T
T
DESCRIPTION: : At high volume with no signal on an un-terminated input analogue input,
there maybe some residual noise from one or more channels
REASON: The residual noise is coming from the DSP PC board and power supply ground.
SOLUTION: Perform the following ground changes to lower residual noise.
1. Cut the wire running to J701 located between JMP119 and JMP161 on the main pc
board, located directly opposite U704 (a regulator tied to heatsink).
May 20.2004 Subject: Residual Noise
Implemented in production from Serial number:
1. From R44T74304001~4500
2. From R44T74305861~6400
3. From R44T74306601~Onwards
YES
NO
2. Cut the ground of the shielded cable J715 between Main board and DSP board, cut
this at the DSP side plug. See figure 1.
Figure 1
Cut this black GND wire
at the DSP side as
shown
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Technical Bulletin T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-01
3. Add a jumper from the Multi channel RCA connector to the Pre Amp RCA connector.
See figure 2.
Figure 2
Multi-channel RCA connector
to Pre Amp RCA connector
GND wire.
Contact:
NAD Electronics International
633 Granite Court
Pickering, ON Canada L1K 3K1
Voice: 905-831-0799 FAX 905-837-6357
www.nadelectronics.com
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Technical Bulletin T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-01
4. Add jumper wire from the DSP board analog ground to the Pre Amp RCA jack. See
figure 3.
5. Add jumper between Preout RCA jack and Surround Power Amp input ground See
figure 3 and figure 4.
Figure 3
Wire from Pre
Amp RCA to
Surround Amp
Contact:
NAD Electronics International
633 Granite Court
Pickering, ON Canada L1K 3K1
Voice: 905-831-0799 FAX 905-837-6357
www.nadelectronics.com
GND wire from
DSP board to Pre
Amp board
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Technical Bulletin T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-01
Figure 4
Wire from RCA connector
GND to Surround Amp GND.
6. Mount the keyboard cable jumper wire to the chassis using the nearest front panel
mounting screw. This originally is tied to the DSP analog ground. See figure 5. Float
the analog ground of the DSP board from chassis.
Figure 5
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Technical Bulletin T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-01
7. There are 2 screws on the DSP board, the one located nearest to volume knob is the
one that has to be isolated. Remove that screw and put an insulator between the PCB
copper side and front panel chassis. See figures 5, 6.
Figure 6
Contact:
NAD Electronics International
633 Granite Court
Pickering, ON Canada L1K 3K1
Voice: 905-831-0799 FAX 905-837-6357
www.nadelectronics.com
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