Engineers frequently have trouble locating the drawings while repairing electronics products, especially older models. There might no longer be any circuit diagrams available at present. Drawing a circuit diagram based on the actual products is therefore required in order to analyze and improve the product. There are different processes used to execute this process few of which are given below. 1. Reasonably divide functional areas When reverse designing the schematic diagram of an intact PCB board. Dividing up functional areas can help engineers avoid unnecessary problems. It also improves the efficiency of drawing. In general, the same functional components on an electronic circuit board will be placed centrally. Dividing areas by function can provide a convenient and accurate basis for reverse analysis of schematics. However, the division of this functional area is not arbitrary. It requires engineers to have a certain understanding of electronic circuit related knowledge. First, find out the core components of a functional unit, and then find out the same function according to the wiring connection，  Other elements of the unit. Form a functional partition (the formation of functional partition is the basis of schematic drawing). In addition, In this process, don’t forget to use the component number on the circuit board wisely, they can help you to partition the function faster. 2. Find the right reference components This reference component can also be said to be the main component for reference at the beginning of schematic drawing. In determining the benchmark , The components are then drawn according to the pins of these reference components. The accuracy of schematic diagram can be guaranteed to a greater extent. For engineers, the determination of reference components is not very complicated, in general, can choose to be the main circuit.  The components to be used as reference components, they are generally larger, more pins, easy to draw, such as integrated circuits, transistors and so on. Can be used as appropriate reference components. 3. Correctly distinguish lines and reasonably draw wiring To distinguish ground cables, power cables, and signal cables, engineers also need to have knowledge of power supplies, circuit connections, PCB wiring knowledge and so on. The distinction of these circuits can be analyzed from the connection of components, the width of copper foil and the characteristics of electronic products themselves. In cabling drawing, in order to avoid line crossing and interspersing, ground symbols can be widely used for ground cables. Various lines can use different colors of different lines to ensure clear discernable, various components can also use special signs, and even the unit circuit can be drawn separately, and then combined. 4. Master the basic framework and refer to similar schematic diagrams For some basic electronic circuit frame composition and principle drawing method, engineers need to master, not only to be able to some Simple, classic basic composition of the unit circuit to draw directly, but also to form the overall framework of the electronic circuit. On the other hand, do not neglect that the same type of electronic products have certain similarities in the schematic diagram.  Engineers can according to the accumulation of experience, full reference to similar circuit diagram to carry out the reverse analysis of the new product schematic diagram. 5. Check and optimize After schematic drawing is completed, testing and verification should be carried out. To calculate the PCB schematic of the reverse design end.  The marking values of components sensitive to PCB distribution parameters need to be checked and optimized, And the schematic diagram should be carried out according to the PCB file diagram Contrastive analysis and check to ensure that the schematic diagram, And document diagram are completely consistent.