There are several possible reasons for this:
1. Whether the transformer of the electronic scale is burned out.
2. Whether the power socket is in poor contact and burned out.
3, D2FR155 diode voltage difference should not be greater than 1V
4, foot about 9V-10V, 4TIP31C triode is bad (E foot about 7V. B pin 8V or so)
5, the battery voltage is too low or bad can not be charged.
6, poor welding.
7, if it does not change color, please check whether the Q5Q6Q7 transistor is good. It is recommended to take it to a repair shop.
Electronics call internal wiring problems
Check the internal lines and replace or repair the corresponding lines. Some cheap electronic scales are shaken during transportation, which will cause the battery line or other lines to break, and it is OK to weld well.