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例一机型:一台红梅WHD-17型14英寸黑白电视机。故障现象:有声无图,但光栅亮度正常,扫描线清晰,无任何杂点条纹。检修过程:根据检修常识判断,有声无图一般说明公共通道没有问题,故障应在预视放电路及其以后的视放电路中。又从光栅上投有任何杂点条纹来判断,视放级多半有开路性故障。因此,首先测量视放管的工作点,结果正常。又查视放管的基极耦合电容和集电极耦合电容,还是正常。进一步测量预视放管的工作点,仍然正常。至此,检修工作一时不知从何下手。在没有办法的情况下只好向预视放以前的公共通道进行搜索检查,结果查出检波二极管的正向电阻
Example a model: a Hongmei WHD-17 14-inch black and white TV. Symptoms: no sound pictures, but the grating brightness is normal, the scan line is clear, without any noise stripes. Maintenance process: According to the maintenance of common sense to judge, there is no picture sound public channel is no problem, the fault should be in the pre-release circuit and its after the release circuit. Again from the grating cast any noise stripes to judge, depending on the release level mostly open-circuit fault. Therefore, the first measurement of the operating point of the tube, the result is normal. Also check the release of the base coupling capacitor and collector coupling capacitor, or normal. It is still normal to further measure the operating point of the pre-exposure tube. At this point, maintenance work temporarily do not know where to start. In the absence of a solution, had to pre-release the public channel before the search inspection, the detection of the detector diode forward resistance