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EWY-103型电子自动电位差计通电预热后,输入信号,仪表指针不指示,检查仪表除了放大器以外的各部分,均正常,因此确定是放大器有问题。用放大器综合测试仪检查,发现:接通电源后,电机顺时针方向慢转,电压表指示为30V,约2秒后,电压表又指零,电机停止转动。进一步分析,其原因是放大器的第三级放大电子管(6N1)左半边的阴极电阻(原理图上的R_(12))变大之故,即按规定该阻值为1kΩ,现增至64kΩ。由于该电阻过大,使阴极发射出来而落在栅极上的少量电子不易
EWY-103-type electronic automatic potentiometer preheat power, the input signal, the instrument does not indicate the pointer, the test instrument in addition to the various parts of the amplifier, are normal, so determine the amplifier is a problem. Amplifier integrated tester inspection and found that: After switching on the power, the motor clockwise slow rotation, voltmeter indicates 30V, about 2 seconds later, the voltmeter refers to zero, the motor stops rotating. Further analysis, the reason is the cathode amplifier (6N1) on the left half of the cathode resistance (R_ (12) on the schematic becomes larger, so that the required value of the resistance of 1kΩ, now increased to 64kΩ. Due to the resistance is too large, the cathode emits a small amount of electrons falling on the gate is not easy