How to tell positive and negative poles in circuit boards?

The way to find the ground on the circuit board:\x0d\1, large area copper foil line is the ground. Usually the ground copper foil is thicker than the average line, and the entire circuit board is connected everywhere \x0d\2, the component metal shell is the ground. Some components of the shell is metal material, such as switch parts, they are in the circuit shell ground wire. \x0d\3, shielded wire metal mesh is the ground. If the circuit board has a metal shield wire, its metal mesh wire is the ground in the circuit board. \x0d\4, the negative plate ground wire of the largest electrolytic capacitor. \x0d\\\x0d\Another: according to the color of your wire to determine the general red to the positive terminal, yellow to the negative terminal. You can compare yourself to see should be clear.