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故障现象:只有白色的光栅,无伴音、无图像。分析与检修:从故障现象分析,开关电源和行电路工作正常。检查微处理器IC001(PCA84CC40)(42)脚(V_(DD)端)无+5V电压,电路如图1所示。查提供+5V的稳压调整管Q015c极无14.5V输入电压。测开关电源14.5V输出电路上的限流电阻R624和整流二极管D608已击穿开路。仔细察看,发现音频功放IC401(TDA1904)②脚(V_(DD)端)的上方塑封面上有一个电击烧焦的小洞孔,测量②脚对地电阻只有2Ω,证实IC401的14V工作电压V_(DD)端对地短路,显然也导致了R624、D608因过流而损坏。更换所损坏的IC401、
Symptoms: only white grating, no sound, no images. Analysis and Maintenance: From the failure phenomenon analysis, switching power supply and the circuit is working properly. Check the microprocessor IC001 (PCA84CC40) (42) feet (V_ (DD) side) no +5 V voltage, the circuit shown in Figure 1. Check to provide +5 V regulator Q015c regulation very no 14.5V input voltage. Measured switching power supply 14.5V output circuit of the current limiting resistor R624 and rectifier diode D608 has been broken open circuit. A closer look, found that the audio power amplifier IC401 (TDA1904) ② feet (V_ (DD) side) above the plastic surface with a charred charring small holes, the measurement of ② feet to ground resistance is only 2Ω, IC401 confirm the 14V operating voltage V_ (DD) end-to-ground short circuit, apparently also led to R624, D608 due to over-current damage. Replace damaged IC401,