A PZ4880-01B four-color machine of the company has an abnormal phenomenon of electric plate-drawing, which has a great impact on the installation time and product quality. We checked the input and output points of the PLC controlled electric pull version, the 24V switching power supply, the pull version relay, the pull version motor, and the related lines of the pull version. Through the inspection, it was found that the load capacity of the 24V switching power supply became worse. The output voltage of the 24V was normal with the digital voltmeter, but the voltage of the electric pull plate fell to about 16V immediately after turning on, and the display lamp of the machine also became dark. In order to accurately determine whether there is a problem with the 24V switching power supply, remove it from the main electrical box, connect the input terminal to 220V voltage, connect the output terminal to the load, a 51Ω, 50W resistance, and connect a 3 ~ 5A ammeter in series to test the result. It was found that when the current was 0.5A, the voltage had dropped to about 16V, and at the same time, the C3459 switch tube became hot, and it was suspected that the tube had a problem. Since the original model transistor could not be purchased, it was replaced with C4111, but the fault was still not eliminated. Also suspected that the switching tube was insufficiently excited, so the push tube D1207 transistor was removed and replaced with the transistor C2271. The fault was eliminated and the temperature of the switch tube returned to normal.
After analysis, the load of this switching power supply has two channels: one is the display light of the whole machine, and the other is to control the electric version. The abnormality of the electric pull version is mainly caused by the poor load capacity of the 24V switching power supply.
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