NAD T-763 Service manual
Technical Bulletin
T763
Date:
Note:
Previous T.B.’s required: Revised from T763-H2005-05
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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
Product: A/V Receiver
Hardware Technical Bulletin: T763-H2005-05R
March 7/05 Subject: Static protection for
muting transistors
Implemented in production from serial number:R49T76305615
YES
NO
muting circuit
Subwoofer/Multi
muting circuit
All other channels
Page 1 of 2
board
Figure 2
Technical Bulletin
T763
Product: A/V Receiver
Hardware Technical Bulletin: T763-H2005-05R
4700pF surface
mount capacitor
between base
and collector
pins of muting
transistor on the
pre amp pc
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 T763
Product: A/V Receiver
Hardware Technical Bulletin: T763-H2004-01
Date: June 15
Note:
Previous T.B.’s required:
T
T
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
Change the cable between J617 on Pre-out board and Multi-channel RCA from AWG22 to
1.
AWG18.
Implemented in production from Serial number: R44T76303751
YES
NO
, 2004 Subject: Residual Noise
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
Page 2 of 4
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