NAD T-743 Service manual
Technical Bulletin
T743
Date:
Note:
Previous T.B.’s required: Revised from T743-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,Q615,Q617.
Figure 1
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2005-05R
March 7/05 Subject: Static protection for
muting transistors
Implemented in production from serial number:R49T74310201
YES
NO
muting circuit
Subwoofer/Multi.
muting circuit
All other channels
Page 1 of 2
Technical Bulletin
T743
Figure 2
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2005-05R
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 T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-03
Date:
Note:
Previous T.B.’s required:
DESCRIPTION: To improve the compatibility of HDTV signals with some TV/Monitors.
REASON: When decoding HDTV signals some TV/Monitors may experience horizontal
sync loss.
SOLUTION: Perform the following change to the Component video board.
On the component video PCB U4301
June 1, 2004 Subject: HDTV Component
Video change
Implemented in production from Serial number: R44 series and onwards
T
T
YES
NO
A) Link the following pins on U4301;
Pins 9 to 10
Pins 12 to 13
Pins 14 to 15
Figure1
Page 1 OF 2
Technical Bulletin T743
Product: A/V Receiver
Hardware Technical Bulletin: T743-H2004-03
HDTV Component Video Change
B) Remove C4317, C4319, C4321.
Figure 2
C) Replace C4316, C4318, and C4320 with 1000 uF 6V.
Figure 3
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
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