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在维修中,发现两台学生示波器的故障,都出在水平扫描级阻容补偿衰减器的云母电容C19上,见下图现将情况介绍如下: 1.x增益调至最大,水平扫描线只能展开一格半.在确定电位器W_8是好的后,我认为问题就是水平放大器放大量不足引起的.根据故障分析,查电压放大和差动放大电子管G_5、G_6的直流工作电压正常;把扫描开关置“外x”档,Y衰减开关置“1000”档,用手摸外x接线柱,同时调整x增益电位器W_8,此时示波管显示的扫描基线能大幅度展开或缩小.可见,故障点不在本级而在前级.用另一台完好的学生示波器查C_(17)两端的锯齿波扫描电压,显示结果有10Vpp
In the maintenance, found that two students oscilloscope failure, are in the horizontal scanning resistance compensation capacitor at the mica capacitor C19, the following figure will introduce the situation as follows: 1.x adjusted to the maximum gain, the horizontal scan line only Can determine the potentiometer W_8 is good, I think the problem is caused by the lack of horizontal amplifier amplification.According to the fault analysis, check the voltage amplification and differential amplification tube G_5, G_6 DC operating voltage is normal; the Scan switch set “external x” file, Y attenuation switch set “1000” file, touch the external x terminal, while adjusting the x gain potentiometer W_8, at this time oscilloscope display scan baseline can greatly expand or contract. Visible, the point of failure is not at this level and in the previous level with another intact student oscilloscope C_ (17) at both ends of the sawtooth wave scanning voltage, the result shows 10Vpp