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[例1]故障现象 一台孔雀牌KQ47—39型彩电,无伴音,其他均正常。 分检与检修 该机采用三洋83P系列机芯,集成电路M51354AP(IC101)和有关外围电路完成图像中放、视频检波、中放及高效AGC、AFT、噪声抑制、伴音中频限幅放大、鉴频、电子音量衰减、音频激励放大等功能。图像彩色均正常,表明图像中放、视频检波、RFAGC、IFAGC、AFT等电路正常,问题发生在伴音中频限幅放大、鉴频、电子音量衰减、音频及功率放大部分。为了判断故障的大体范围,接通电源,从IC101(17)脚(音频信号输出脚)注入感应信号,喇叭有响声,说明该机功率放大电路IC171(LA4265)正常。从IC101(18)脚(伴音中放信号输入脚)注入感应信号,喇叭无响声,说明问题出在伴音限幅中放、鉴频、电子音量衰减和音频激励等电路中。
[Example 1] Failure phenomenon A Peacock brand KQ47-39-type TV, no sound, the other are normal. Separation and maintenance of the aircraft using the Sanyo 83P series movement, integrated circuit M51354AP (IC101) and the external circuit to complete the image in the put, video detection, and put in and efficient AGC, AFT, noise suppression, audio intermediate frequency limiting amplification, , Electronic volume attenuation, audio excitation amplification and other functions. Image color are normal, indicating that the image release, video detection, RFAGC, IFAGC, AFT and other circuits are normal, the problem occurs in the audio intermediate frequency limiting amplification, frequency discrimination, electronic volume attenuation, audio and power amplification. In order to determine the general scope of the fault, turn on the power, the induction signal from the IC101 (17) feet (audio signal output pin), the speaker has a sound, indicating that the machine power amplifier IC171 (LA4265) normal. Induction signal is injected from IC101 (18) feet (sound input signal input pin), the speaker does not sound, indicating that the problem lies in the circuit of sound limiting amplitude release, frequency discrimination, electronic volume attenuation and audio excitation.