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万用表是检修电视机的常用工具,但在使用万用表测量通电线路时会改变电路的某些参数,造成修理人员的错误判断。下面试举两例,供读者参考。例一:有电视机一台,图象不稳,有网纹干扰,部分中放电路如图1。一中放基极偏置电压取自二中放发射极,但用MF-10型表检测电压时,二中放发射极B点为3.8V, 一中放基极A点却为4. 3V。A点除了经由R_1、R_2馈入的电压外别无通路,为何二中放发射极电压经隔离电阻后反而升高?
Multimeter is a common tool to repair TV, but the use of multimeter to measure the power line will change some of the parameters of the circuit, resulting in the wrong judgment of the repair personnel. Cite two cases below, for readers reference. Example 1: There is a TV set, the image is not stable, there are textured interference, part of the discharge circuit shown in Figure 1. One put the base bias voltage taken from two in the emitter, but with the MF-10 type table test voltage, the second put the emitter B point is 3.8V, put in the base A point is 4. 3V . A point in addition to the voltage fed through R_1, R_2, respectively, there is no pathway, why the emitter voltage in the middle of the isolation resistance but increased?