NAD-T773-avr-tb4 维修电路原理图.pdf

Page 1 of 2 Technical Bulletin T773 Product: A/V Receiver Hardware Technical Bulletin: T773-H2005-05R Date: March 7/05 Subject: Static protection for muting transistors Note: Implemented in production from serial number:R49T77302671 Previous T.B.s required: Revised from T773-H2005-05 K K K K YES K K K K 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. s muting circuit All other channels RadioFans.CN 收音机爱 好者资料库Page 2 of 2 Technical Bulletin T773 Product: A/V Receiver Hardware Technical Bulletin: T773-H2005-05R 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 and collector pins of muting transistor on the pre amp pc board RadioFans.CN 收音机爱 好者资料库