- Appearance inspection method
Observe whether there are scorched places on the circuit board, broken places on the copper coating, peculiar smell on the circuit board, bad welding places, mildew and blackness on the interface and gold finger, etc.
Circuit board maintenance
- Pass kill method
All components shall be tested until the defective components are found, so as to achieve the purpose of repair. In case of components that cannot be detected by the instrument, new components shall be used to replace them, so as to finally ensure that all components on the board are good, so as to achieve the purpose of repair. This method is simple and effective, but it is powerless to solve the problems such as through hole impassability, copper coating fracture, improper potentiometer adjustment, etc.
- Comparison method
The comparison method is one of the most commonly used methods for maintenance of circuit boards without drawings, which has been proved to be very effective in practice. The purpose of finding faults is achieved by comparing the status of good boards with that of good boards. Abnormalities are found by comparing the curves of each node of two boards.
- State method
The state method is to check the normal working state of each component. If the working state of a component does not conform to the normal state, there is a problem with the component or its affected components. The state method is the most accurate one among all maintenance methods, and its operation difficulty is beyond the grasp of ordinary engineers, which requires rich theoretical knowledge and practical experience.
- Grounding circuit method
The circuit building method refers to the method of making a circuit by hand, which can work after installing the missing integrated circuit, so as to verify the quality of the tested integrated circuit. The accuracy of this method can reach 100%, but it is difficult to build a set of circuits for all ICs with various types and complex packaging.
- Principle analysis method
This method is to analyze the working principle of a board. For engineers, some boards, such as switching power supply, can know their working principles and details without drawings. For engineers, things that know their schematic diagrams are extremely simple to maintain.