NAD-T753-avr-tb5 维修电路原理图.pdf

Page 1 of 2 Technical Bulletin T753 Product: A/V Receiver Hardware Technical Bulletin: T753-H2005-07 Date: February 28/05 Subject: Static protection for muting transistors Note: Implemented in production from serial number:R4XT75312375 Previous T.B.s required: ? ? 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 channels 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 Subwoofer/Multi CH. smuting circuit All other channels RadioFans.CN 收音机爱 好者资料库Page 2 of 2 Technical Bulletin T753 Product: A/V Receiver Hardware Technical Bulletin: T753-H2005-07 Figure 2 Contact: NAD Electronics International 633 Granite Court Pickering, ON Canada L1K 3K1 Voice: 905-831-0799 FAX 905-837-6357 4700pF surface mount capacitor between base emitter pins of muting transistor on the pre amp pc board RadioFans.CN 收音机爱 好者资料库