NAD T-753 Service manual
Technical Bulletin
T753
Date:
Note:
Previous T.B.’s required: Revised from T753-H2005-07
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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: T753-H2005-07R
March 7/05 Subject: Static protection for
muting transistors
Implemented in production from serial number:R4XT75312375
YES
NO
muting circuit
Subwoofer/Multi
muting circuit
All other channels
Page 1 of 2
board
Figure 2
Technical Bulletin
T753
Product: A/V Receiver
Hardware Technical Bulletin: T753-H2005-07R
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
T753
Date:
Note:
Previous T.B.’s required:
❑❑❑❑
❑❑❑❑
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
Product: A/V Receiver
Hardware Technical Bulletin: T753-H2005-06
February 28/05
Implemented in production from serial number:R44T75307875
YES
NO
Subject:
Intermittantly shuts down
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
Product: A/V Receiver
Hardware Technical Bulletin: T753-H2004-02
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 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
Implemented in production from Serial number: R44T75307575
YES T753H2004-01
NO
, 2004 Subject: Residual Noise
Page 1 of 5
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