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故障现象:导联开关置定标位置时打不出定标,描记为光滑直线。导联开关置Ⅰ导联时既打不出定标也无心电信号描记,描记亦为光滑直线。导联开关置其它各导联时打定标和心电信号描记均正常。故障时有时无。分析检修:除定标和Ⅰ导联位置加不进信号外其它各导联都正常,说明从输入到输出的各电路均能正常工作。根据故障现象,Ⅰ导联加不进信号的原因只能是导联开关接触不良或封闭电路有故障,无定标的原因只能是定标电路本身有故障或封闭电路有故障;而在其它导联能打定标则说明定标电路并无故障,描记为一光滑的直线则说明前置放大器的输入端不会悬空。所以可以初步断定,故障原因在于导联开关在定标和Ⅰ导联的位
Symptom: When the lead switch is set to the calibration position, the calibration is not available and the trace is smooth. When the lead switch is set to I lead, neither the calibration nor the ECG signal tracing is performed, and the tracing is also a smooth straight line. When the lead switch is set to other leads, the calibration and ECG traces are normal. There are sometimes no faults. Analysis and maintenance: In addition to calibration and I lead position plus non-advanced signals, all other leads are normal, indicating that all circuits from input to output can work normally. According to the phenomenon of failure, the cause of the I-lead plus non-advanced signal can only be the poor contact of the lead switch or the failure of the closed circuit. The reason for the non-calibration can only be that the calibration circuit itself is faulty or the closed circuit is faulty; The lead can be calibrated to indicate that the calibration circuit is free of faults, and a smooth straight line indicates that the input of the preamplifier does not float. So we can preliminarily conclude that the cause of the fault lies in the position of the lead switch in the calibration and I leads.