Technical Bulletin T763
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Product: |
A/V Receiver |
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Hardware Technical Bulletin: T763-H2005-05R |
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Date: |
March 7/05 |
Subject: Static protection for |
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muting transistors |
Note: |
Implemented in production from serial number:R49T76305615 |
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Previous T.B.’s required: Revised from T763-H2005-05
YES
NO
DESCRIPTION: You may have the complaint that the subwoofer or other channels are popping when switching inputs or when turning on and off.
REASON: The channel that is popping may have a muting transistor damaged due to an external source or subwoofer causing static damage to the transistor.
SOLUTION: Replace the transistor and install a 4700 pF capacitor between the base and collector on the pre amp pc board , as shown in the following two schematics. The use of a surface mount capacitor is recommended. Placing the capacitor on the bottom of the board between the base and collector of each muting transistor is preferred . See figure 2 on page 2.
Note: It is recommended to install this capacitor to each channel’s muting transistor. The following are the designations of the muting transistors, Q608,Q609,Q610,Q611,Q612,Q613,Q615,Q617 and Multi source muting transistors Q632,Q633.
Figure 1 |
muting circuit |
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muting circuit |
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Subwoofer/Multi |
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All other channels |
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CH. ‘s |
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Page 1 of 2
Technical Bulletin T763
Product: A/V Receiver
Hardware Technical Bulletin: T763-H2005-05R
Figure 2
4700pF surface mount capacitor between base and collector pins of muting transistor on the pre amp pc board
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 T763
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Product: |
A/V Receiver |
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Hardware Technical Bulletin: T763-H2004-01 |
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Date: |
June 15, 2004 |
Subject: Residual Noise |
Note: |
Implemented in production from Serial number: R44T76303751 |
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Previous T.B.’s required:
TYES
TNO
DESCRIPTION: At high volume setting with no signal on an un-terminated analogue input, there maybe some audible residual hum noise and whistling sound coming from one or more channels.
REASON: The residual noise is coming from power supply ground and DSP board ground. The whistle noise is coming from the DSP board.
SOLUTION: Remove the DSP board and order a replacement DSP board from our spares department .Order under the number in the service manual. Perform the following ground changes to lower residual hum noise.
T763 Ground changes
1.Change the cable between J617 on Pre-out board and Multi-channel RCA from AWG22 to AWG18.
Figure 1
Note: If this is not present on the unit, add AWG18 cable between Pre-out RCA and Multichannel RCA.
Page 1 of 4
Technical Bulletin T763
Product: A/V Receiver
Hardware Technical Bulletin: T763-H2004-01
T763 Ground Changes
2. For J705B on AUDIO PCB, cut all the AGND pin. That is pin 1, 3, 9 & 12. Please refer to figure 2.
Figure 2
3. Install a 18AWG ground wire from the DSP board to the Multi channel RCA connector ground. See Figure 3.
Figure 3
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