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故障现象 开机时机内发出继电器反复连续分离、吸合的“嗒嗒”响声,电视机呈“三无”状态。 分析与检修 先例开关电源变压器次级绕组+B及其它几组的输出电压,均在正常值附近随着继电器连续的分离、吸合而跳动。测D板行扫描输出管Q2591(2SC4927)的基极,发现无-0.2V电压,用示波器观测亦无行扫描推动脉冲。测行推动管Q2502(2SC2688)基极亦无波形。此行扫描推动脉冲信号
Fault phenomenon The relay is issued repeatedly during the boot time, pull the clatter “sound”, the TV was “three noes” state. Analysis and Overhaul precedent Switching Power Transformer secondary winding + B and other groups of output voltage, are in the vicinity of normal with the relay continuous separation, pull and jump. Measure the base of the Q2591 (2SC4927) of the D-line scan output tube and find that there is no -0.2V voltage, and the oscilloscope does not use the line scan to push the pulse. Test drive line Q2502 (2SC2688) has no waveform at the base. This line scan drives the pulse signal