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一台PZ12a型双积分式数字电压表时好时坏,工作不正常。经检查发现,供给基准源,内控电路和积分器的-24V的内部电源,在不正常时为-15.1 V,与正常值相差8.9V。为了确定是电源本身还是负载问题,我们将所有-24V负载全部断开,重新测量仍为15.1 V,断定为电源本身有问题。进一步查找发现,电源复合推动管BG10性能不佳,用图示仪测β值只有15倍。由下图可知,-24V电源是以+24V电源通过接到BG7基极的电阻R 和
A PZ12a double integral digital voltmeter good and bad, not working properly. The inspection revealed that the -24V internal power supply to the reference source, the internal control circuit and the integrator was -15.1 V in case of abnormality, which is different from the normal value of 8.9V. In order to determine whether the power itself or the load problem, we will all -24V load all disconnected, the re-measurement is still 15.1 V, concluded that there is a problem with the power supply itself. Further search found that the power complex to promote tube BG10 poor performance, measured by the instrument measured beta value of only 15 times. It can be seen from the figure below, -24V power supply is based on the +24 V power received by the BG7 base resistor R and