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机型:富丽VIP-1000(VCP-777) 故障1:重放图象正常,伴音发闷,音量也较正常时小。 分析与检修:据用户反映,该故障已经多次在多处修理,但均未修复。根据故障现象分析:声音发闷,是因电路高频特性不佳,这说明在信号通道中可能存在一高频衰减因素,而放大器中的原件(尤其是电容)均代换过,故障不在音频电路本身。于是怀疑音频抑制电路有问题,断电测量V_(Q401)集电极对地电阻,发现阻值较小,且稳定不变,这是不应有的现象,因V_(Q401)(音频抑制管)集电极直流状态属开路(悬空),对地电阻应无穷大(见图1)。焊下该管测
Model: Fuli VIP-1000 (VCP-777) Fault 1: playback image is normal, sound boring, the volume is smaller than normal. Analysis and Maintenance: According to the user, this fault has been repaired many times in many places, but it has not been repaired. According to the failure phenomenon analysis: sound dull, because the circuit high-frequency characteristics of poor, indicating that there may be a signal path in the high-frequency attenuation factor, and the original amplifier (especially the capacitor) have replaced, the fault is not audio The circuit itself. So I suspect the audio suppression circuit has a problem, measure the V_ (Q401) collector to ground resistance and found that the resistance is small, and stable, this is an unworthy phenomenon, due to V_ (Q401) (audio suppression tube) Collector DC state is open (dangling), to ground resistance should be infinite (see Figure 1). Welding under the tube test