Technical Bulletin T753
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Product: |
A/V Receiver |
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Hardware Technical Bulletin: T753-H2005-07R |
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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:R4XT75312375 |
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Previous T.B.’s required: Revised from T753-H2005-07
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 T753
Product: A/V Receiver
Hardware Technical Bulletin: T753-H2005-07R
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
Page 2 of 2
Technical Bulletin T753
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Product: |
A/V Receiver |
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Hardware Technical Bulletin: T753-H2005-06 |
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Date: |
February 28/05 |
Subject: |
Intermittantly shuts down |
Note: Implemented in production from serial number:R44T75307875
Previous T.B.’s required:
YES
NO
DESCRIPTION: Unit may shut down, shortly after turn on.
REASON: There is a diode on the standby board that maybe operating intermittantly.
SOLUTION: Locate and identify D756 on the standby board. Change only if the diode is a 1N4148. Change from a 1N4148 to a 1N4001 or equivalent. See figure 1 for details.
Figure 1
D756 CHANGE FROM 1N4148 TO 1N4001
Contact:
NAD Electronics International 633 Granite Court
Pickering, ON Canada L1K 3K1
Voice: 905-831-0799 FAX 905-837-6357 www.nadelectronics.com
Page 1 of 1
Technical Bulletin T753
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Product: |
A/V Receiver |
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Hardware Technical Bulletin: T753-H2004-02 |
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Date: |
June 15, 2004 |
Subject: Residual Noise |
Note: |
Implemented in production from Serial number: R44T75307575 |
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Previous T.B.’s required:
T YES T753H2004-01
TNO
DESCRIPTION: At high volume setting with no signal on an un-terminated analogue input, there maybe some residual noise coming from one or more channels.
REASON: This residual noise is coming from the DSP PC board and power supply ground.
SOLUTION: Perform the following ground changes to lower residual noise.
1.Add jumper wire between DSP AGND (grounding bracket) and Multi-channel RCA (the blue wire in the photo, use AWG #18). See Figure 1.
Figure 1
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