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故障现象按“ADV”、“RED”导联转换键不起作用,LED 显示状态停于“TEST”位置。故障分析及检修从故障现象判断故障发生在可逆计数器电路(见附图)。根据计数器电路原理分析,四位二进制可预置可逆计数器(IC_(2/2))的尺端,只有在开机后的瞬间和“ADV”键揿欠动第十三次后 IC214的 Q_5=1时为高电平,计数器被复位,导联状态和 LED 显示状态处于“TEST”位。其余时间均处于低电平状态时,才能使
Symptom Press the “ADV”, “RED” lead conversion key does not work, LED display state stopped at “TEST” position. Fault Analysis and Maintenance Judging from the fault phenomenon, the fault occurs in the reversible counter circuit (see attached figure). According to the counter circuit principle analysis, four binary preset reversible counter (IC_ (2/2)) feet, and only after the boot moment and “ADV” key owe move the thirteenth IC214 Q_5 = 1 When high, the counter is reset, lead status and LED display status is in “TEST” position. The rest of the time in low state, can make