1. Visual inspection method

By observing whether there is a burnt place on the circuit board, whether there is a broken place in the copper coating, whether there is a peculiar smell on the circuit board, whether there is a bad soldering place, whether the interface, gold finger is moldy and black, etc.

2. Total inspection

Check all the components until the problematic component is found to achieve the purpose of repair. If you encounter a component that cannot be detected by the instrument, replace it with a new component to ensure that all components on the board are good. The purpose of repair. This method is simple and effective, but it is powerless to solve problems such as blocked vias, broken copper, and improper adjustment of the potentiometer.

3. Contrast method

The comparison method is one of the most commonly used methods for repairing circuit boards without drawings. Practice has proved to have very good results. The purpose of detecting faults is achieved by comparing the status of the good boards. The abnormalities are found by comparing the curves of the nodes of the two boards. .

4. State method

The state method is to check the normal working state of each component. If the working state of a certain component does not match the normal state, there is a problem with the device or its affected parts. The state method is the most accurate method of all maintenance methods, and its operation difficulty is not that ordinary engineers can master. It requires a wealth of theoretical knowledge and practical experience.

5. Circuit method

The circuit method is a method of making a circuit by hand, which can work after the integrated circuit is installed, so as to verify the quality of the tested integrated circuit. This method can achieve 100% accuracy, but the tested integrated circuits have many types and complex packaging. It is difficult to build a set of integrated circuits.

6. Principle analysis method

This method is to analyze the working principle of a board. For some boards, such as switching power supplies, engineers can know the working principle and details without drawing. For engineers, it is very simple to repair things that know the schematic.