Eight methods to reconstruct the PCB schematic diagram following the specifications of the PCB board

1. Choose electronic components with a large volume and multiple pins, such as integrated circuits, transformers, transistors, and others that are crucial in the circuit. Then, proceed to derive from the chosen reference pins to minimize mistakes.
2. If the PCB is labeled with component identifiers (like VD30, R790, C863, etc.), it’s important to note that these identifiers follow a set pattern. Components that share the same numerical digits after the initial letter(s) belong to the same functional group. Therefore, when creating the PCB layout, it’s essential to accurately identify and differentiate between components within the same functional group.
3. In cases where component serial numbers are not indicated on the printed board, it’s advisable to assign your own numbers to the components to facilitate straightforward analysis and verification. Typically, when designing printed circuit board components, manufacturers will position components that are part of the same functional unit in close proximity to reduce the length of copper foil connections. Identifying the core functional device is key; once located, it becomes easier to locate the remaining components belonging to that same functional unit.
4. It’s important to accurately identify the ground wire, power line, and signal line on the printed circuit board. Let’s consider the power supply circuit as an example. The negative terminal of the rectifier, which is connected to the power transformer’s secondary, serves as the power supply’s positive terminal. Typically, a high-capacity filter capacitor is connected between the ground and the ground, and the capacitor’s casing has a polarity indicator. The power line and the ground wire can be identified from the pins of the three-terminal voltage regulator. When the printed circuit board is routed in the factory, the ground copper foil is usually made the widest to prevent self-excitation and interference (high-frequency circuits often have a large area of grounded copper foil). The power copper foil is the second widest, and the signal copper foil is the narrowest. Furthermore, in electronic products that contain both analog and digital circuits, the printed board often separates its ground wires to create an independent grounding grid. This can also serve as a basis for identification and judgment.
5. To prevent the circuit diagram from becoming cluttered due to excessive component wiring and overlapping circuit lines, it’s advisable to make extensive use of terminal markers and grounding symbols for the power line and ground wire. If the circuit has numerous components, it can be helpful to draw the unit circuits separately and then merge them together.
6. When creating a sketch, it’s suggested to utilize transparent tracing paper and color-code the ground wire, power line, signal line, and components using colored pens. As modifications are made, intensify the color gradually. This approach enhances the visual impact of the drawing and simplifies circuit analysis.
7. Becoming adept at understanding the fundamental structure and traditional sketching techniques of certain unit circuits, such as rectifier bridges, voltage regulator circuits, operational amplifiers, and digital integrated circuits, is beneficial. These unit circuits are sketched directly to establish the circuit diagram’s framework, thereby enhancing the efficiency of the drawing process.
8. While sketching a circuit diagram, it’s beneficial to refer to the circuit diagrams of analogous products. This approach can yield double the output with just half the input.