How to repair the fault of knife grinder?

1.Fault Symptom:

Can't turn the knife properly, can't sharpen the knife.

Analysis and maintenance: power on the test machine in a quiet environment, the correct operation of each function switch on the panel can work flexibly. At the same time, carefully observe each function indicator light, on, off is normal, carefully listen to the machine relay, travel switch, mechanical transmission parts, no abnormal sound, also did not smell any burnt smell. From the above inspection can be determined that the control circuit is basically normal, so disconnect the power supply, open the front panel to check the internal fault point. When the power is on, the knife turning motor runs normally, but the knife sharpening motor does not move at all. Take off the transmission belt, and at the end of the knife turning action, the finger gently moves the knife grinding motor flywheel, at this time the motor can operate at a normal speed. Measuring the dc resistance of the main winding (M,C end) of the motor is about 80, the winding (S.C end) of the motor is about 216,(M,S end) of the motor is about 295, which indicates that the motor is normal, and then start the capacitor at both ends of the capacitor C, the capacity is positive infinity, indicating that the capacitor has been open, remove it and look as expected the outer wall bulges up a large block. Pull the same type capacitor after the test machine, the whole machine resumed normal work.

Special hint: do not power on the test machine for a long time when this kind of fault occurs, so as not to destroy the motor winding because of heavy overload.

2. Fault Symptom:

Can't grind normally, but can only choose 5s or manual shift.

Analysis and maintenance: Connect the power test machine, the function switch on the front panel is flexible. When you press 5. The function indicator on the rice is on and off normally. And it can automatically turn the knife after 5s, and the grinding disc stops turning in the process). When pressed down for 10s or 25s, it can only keep grinding the knife in the position where the knife stopped for a long time on one side. However, it can also turn the knife normally when the manual shift is pressed. According to the above phenomenon, it can be preliminally determined that the fault occurred in the control circuit of the front stage. Open the front panel and find the key components on the switch according to the circuit diagram. There are no virtual welding, diswelding and wire breaking points.