故障现象:一台XDH-3型心电图机在每秒50毫米走纸速度档时运转正常,而在每秒25毫米档时走纸停止。检修分析:首先检查该机走纸变速有关电路,如图1所示。测得电机在每秒50毫米档正常运转时,公共端对另二个引线端的电压分别是约170X和120X,符合规定电压。而在发生走纸故障的每秒25毫米档时电压发生异常,170X降为约135X,120X降为约87X。更换电机后,两档走纸动作又均正常,因此估计故障发生在电机上。 Symptom: An XDH-3 electrocardiograph operates normally at 50 mm per second, and stops at 25 mm per second. Maintenance Analysis: First check the machine take the paper speed-related circuits, as shown in Figure 1. Measured motor 50 millimeters per second during normal operation, the public end of the other two lead voltage is about 170X and 120X, in line with the provisions of the voltage. In the event of paper failure 25 millimeters per second when the voltage anomalies, 170X dropped to about 135X, 120X down to about 87X. After replacing the motor, two steps of paper movements are normal, it is estimated that the fault occurred in the motor.