NAD-T743-avr-tbh200401 电路图 维修手册.pdf

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1、Page 1 of 5 Technical Bulletin T743 Product: A/V Receiver Hardware Technical Bulletin: T743-H2004-01 Date:May 20.2004 Subject: Residual Noise Note:Implemented in production from Serial number: 1. From R44T743040014500 2. From R44T743058616400 3. From R44T74306601Onwards Previous T.B.s required: ? ?

2、YES ? ? NO 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 resi

3、dual 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). 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

4、this black GND wire at the DSP side as shown RadioFans.CN 收音机爱 好者资料库 Page 2 of 5 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 Contact: NAD Electronics

5、 International 633 Granite Court Pickering, ON Canada L1K 3K1 Voice: 905-831-0799 FAX 905-837-6357 Multi-channel RCA connector to Pre Amp RCA connector GND wire. RadioFans.CN 收音机爱 好者资料库 Page 3 of 5 Technical Bulletin T743 Product: A/V Receiver Hardware Technical Bulletin: T743-H2004-01 4. Add jumper

6、 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 Contact: NAD Electronics International 633 Granite Court Pickering, ON Canada L1K 3K1 Voice: 905-831-0799 FAX 90

7、5-837-6357 GND wire from DSP board to Pre Amp board Wire from Pre Amp RCA to Surround Amp RadioFans.CN 收音机爱 好者资料库 Page 4 of 5 Technical Bulletin T743 Product: A/V Receiver Hardware Technical Bulletin: T743-H2004-01 Figure 4 6. Mount the keyboard cable jumper wire to the chassis using the nearest fro

8、nt 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 Wire from RCA connector GND to Surround Amp GND. Page 5 of 5 Technical Bulletin T743 Product: A/V Receiver Hardware Technical Bulletin: T743-H2004-

9、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