1 故障现象开机后,做I、Ⅱ、Ⅲ导联时,导联指示灯亮,按1mV定标键,有定标信号,但无心电信号,其余导联心电信号正常。2 故障分析与排除从故障现象看,应属导联选择电路故障。该机导联输入电路由IC103~IC106组成。开关的转换是由A、B端与IN端子(即禁令控制端)的输入编码来实现的。IC110的A、B、C、D四个逻辑门和IC111的两个逻辑门组成导联选择电子开关的逻辑控制电路。它把键控电路 1 fault phenomenon After the boot, do I, II, III lead, the lead indicator light, according to 1mV scaling key, there is a calibration signal, but no ECG signal, the rest of the lead ECG signal is normal. 2 Fault Analysis and Troubleshooting From the perspective of fault phenomena, the lead selection circuit should be faulty. The lead input circuit of the aircraft is composed of IC103~IC106. The switching of the switch is implemented by the input codes of the A and B terminals and the IN terminal (ie, the banned control terminal). The four logic gates A, B, C, and D of the IC 110 and the two logic gates of the IC 111 constitute a logic control circuit for selecting the electronic switch of the lead. It has keyed circuits