Why Reverse Engineer a PCB?
When faced with a broken or outdated Printed Circuit Board (PCB), you may consider reverse engineering it. Although it may seem like a time-consuming and challenging process, there are several reasons why you may want to invest in it.
- Essential Functionality: If the PCB powers a crucial electronic component or piece of machinery, it may be worth preserving. For older equipment and vehicles, replacements for outdated PCBs may be unavailable or out of your budget. Therefore, reverse engineering may be a cost-effective solution.
- No Documentation/Data Exists: When you lack the documentation to repair a PCB, reverse engineering may become necessary. While modern PCBs usually have CAD data or some type of documentation, older models may not. In such cases, reverse engineering allows you to create your own data.
- No Professional Knows What to Do with It: Sometimes, no professional or manufacturer is available to troubleshoot and repair a PCB. This may be because the manufacturer is no longer in business or the engineer is deceased.
How to Reverse Engineer a PCB
To reverse engineer a PCB, you need to follow three primary steps:
- Reverse Bound Constructing: You need well-lit and accurate images of both sides of the PCB to create a layout for developing a schematic. For a basic board, you can use graph paper to draw the layout. For more complex PCBs, you can create a line drawing or use photographs to capture the details.
- Build the Layout: For complex PCBs, you need to convert bitmap images to vector graphics and perform multiple editing steps before creating a schematic. Editing steps include painting the holes and solder pads, removing trackpads, marking free holes, and adjusting layers and saturation.
- Derive Schematics: The final step involves deriving a schematic using specific programs such as AutoTrace or a PCB layout CAD program. You need to combine both sides, label components with symbols, and arrange tracks in a sensible and easy-to-interpret way. However, hidden connections may cause discrepancies while troubleshooting.
Conclusion:
Reverse engineering a PCB can be a cost-effective solution when replacements for outdated PCBs are unavailable or out of your budget. With well-lit images and accurate data, you can create a schematic that preserves the essential functionality of the PCB.