电子测量仪器有时会出现时有时无这样一种没有规律的故障现象。产生此情况的主要原因是,由于焊点或接插件接点不良、印刷电路板有裂缝,连接导线断路(但绝缘皮未断)、微调电阻(或电位器)滑动接点接触不良,电容漏电或晶体管、线圈、阻容元件内部接触不良等原因所造成。在检修时,若故障突然消失,就可有目的地轻轻敲打有怀疑的部位,再轻轻摇晃(或用手指轻弹)这部分的元件,使故障再现,以便找出问题所在。这种方法虽不能直接排除故障,但可了解故障及故障现象的变化情况,以便于及时排除故障。例如,一台ZC17型兆欧表,表针指示时有时无,当敲打线路板一些元件时,对故障无影响,而当敲击输出变压器时,对故障影响很灵敏。经查,该变压器B_2内部有断线现 Electronic measuring instruments sometimes appear sometimes without such a phenomenon of irregular failure. The main reason for this is due to poor solder joint or connector contacts, cracks in the PCB, disconnection of the connection leads (but without insulation), poor contact of the trimming resistor (or potentiometer) slip contact, capacitive leakage or transistor , Coil, RCA internal components such as poor contact caused by the reasons. During maintenance, if the fault suddenly disappears, you can purposely tapping the suspicious parts gently, and then gently shake (or finger flick) the parts of this part, the fault reproduction, in order to find out the problem. Although this method can not be directly troubleshooting, but you can understand the failure and failure phenomenon changes in order to promptly troubleshoot. For example, a ZC17 megohmmeter, the mere absence of the needles indicates that when knocking on some components of the circuit board, it has no effect on the fault, and when knocking on the output transformer, the impact on the fault is very sensitive. The investigation, the transformer B_2 internal disconnection now