1: Press the Clear key on the operation panel. Please refer to the next item, 2: Disassemble the back cover, and you will see a motor vertically fixed in the middle part, next to a compass and a pole, and a thick spring (actually two springs, one at the back) is hung on it. Inspection: firstly, check whether the spring is broken (this is easy to see), and secondly, check whether the teeth of the compass and rod are scratched. Check the gear under the motor again for serious wear. Take your time.