Identifying a component on a PCB requires more than recognizing its shape. The same package can contain many different devices, and a short marking may not be a full part number. Combine the board documentation, component markings and electrical context before selecting a replacement or drawing a conclusion about a fault.
Start with the board reference
Find the reference designator beside the component and locate it in the schematic or BOM. References such as R, C or U are useful conventions, but their exact use depends on the design. Confirm the board revision and assembly variant so the documentation describes the fitted unit.
If the marking is difficult to read, use suitable lighting and magnification without scraping the package. Record the full marking, logo, package dimensions and pin count. A photograph of the whole surrounding circuit is often more useful than a cropped image of one code.
Use manufacturer lookup tools
For known TI devices, the TI part-marking lookup accepts package markings or part numbers. Similar manufacturer resources can help narrow candidates. A match must still be checked against the package and pin functions; short codes can be ambiguous across manufacturers.
| Evidence | What it can establish |
|---|---|
| BOM entry | The part intended for that reference and revision |
| Top marking | A candidate device or production identification |
| Package drawing | Pin positions, body dimensions and orientation |
| Surrounding circuit | Whether the candidate function fits the connections |
| Electrical measurement | Behavior under the measurement conditions |
Recognize what cannot be read visually
Small passive components may carry no usable value marking. Color and size alone do not establish capacitance, voltage rating or tolerance. Even when a meter measures one property, it may not reveal the original specification or suitability in the circuit.
Measurements made in circuit can include parallel paths and semiconductor junctions. Disconnect power and discharge stored energy before resistance or continuity checks. Interpret the result using the schematic rather than assuming every low reading means a shorted component.
Approve a replacement deliberately
- Confirm the intended part and the reason it is suspect.
- Compare electrical function and operating limits.
- Verify package, pinout and polarity.
- Review application-specific properties and required approvals.
- Record the substitution and test the affected function.
A damaged component can be a symptom of another fault. Check the surrounding circuit and supply conditions before replacing it repeatedly. For an undocumented or safety-critical assembly, obtain qualified repair support rather than improvising a substitute.
The component selection guide explains the specifications behind common parts, and the BOM guide helps make future identification less dependent on markings alone.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist