Fix a single girder overhead travelling crane, discovered upon examination can only be falling not rising, rising AC contactor doesn't pull-in.

Jog control schematic diagram as shown above. Limit switch contacts inside see figure below. Check control circuit and rise of AC contactor is not abnormal. For a short time back to work, will increase control circuits and control circuits for the test increased by contactors or not to snap. Although this has been basically ruled out the possibility that contactor failure, but in order to further confirm that happen to have the same type of AC contactor, replacement fault found intact.

Repair deadlock. So while pressing up and press down. Accidentally discovered by sparking up time limit switch, opening limit switch and found contact limit switch up bodies burned, identified as limit switch failure. Replace the model with the LX44-40A fault of firearms (limit switches) the test run after returning to normal.