Resistance of various electronic components
What are the failure characteristics of different electronic components?
Every component has a lifespan, and some can last for a long time. The longevity of an electronic component depends on its design, material properties, environmental conditions, and its role within the circuit. Just like humans, some components are more robust than others. For example, in cold weather, some parts may not withstand temperature fluctuations and fail, while stronger ones remain unaffected. This is similar to how human health is influenced by one's constitution.
There are also "strong" components in a circuit. Among them, semiconductor devices such as diodes, transistors, field-effect transistors (FETs), and integrated circuits (ICs) are more prone to failure under normal operating conditions. Therefore, when troubleshooting, it's essential to check these components first. When a semiconductor device fails, breakdown is common. Using a multimeter’s diode test function, you should see a minimum voltage drop across any two terminals—typically around 0.5V. If the reading is significantly higher or lower, the component may be faulty and should be tested further.
Just like scorpions that risk their lives to protect the group, certain components in a circuit are placed in high-risk positions. Components operating under high voltage, current, or power are subjected to greater stress and are more likely to fail. These are often critical parts of the system, so their failure can lead to serious issues.
Heat is a major factor in component failure, especially when large currents flow through them (Joule’s Law: heat is proportional to the square of the current). Components with heat sinks are considered consumables, and high-power resistors are also wear items. A larger physical size usually indicates a higher power rating. Fuses and circuit breakers are among the most vulnerable parts, as they are designed to melt quickly and protect other components. Their low melting point makes them susceptible to failure, but this is part of their protective role.
Components can fail in several ways: overvoltage, overcurrent, and mechanical damage. Overvoltage failures, such as those caused by lightning strikes or rectifier breakdowns, often result in internal damage without visible signs. Overcurrent failures, like thermal breakdown in display tubes, usually show visible signs such as discoloration, cracks, or even burnt areas on the board.
When testing components, a digital multimeter can help identify issues. For resistors, a simple resistance test is sufficient. Diodes can be checked by measuring the voltage drop across the PN junction. Transistors can be tested by checking the condition of both PN junctions. For FETs, the body diode and gate-source/drain connections should be examined. Capacitors may show leakage, short circuits, or open circuits, while inductors may have open windings. Integrated circuits are more complex, and damage can be either total or partial. In cases of poor thermal stability, cooling the IC with alcohol during operation can help determine if the failure is temperature-related.
In general, faults can be categorized into three types: open circuits due to poor contact, component damage, or software issues. Open circuits, such as broken wires or loose connections, are usually easier to fix. However, component damage—especially subtle issues like internal breakdown—is harder to detect without proper tools. Understanding the behavior of each component is crucial for effective troubleshooting and improving repair efficiency.
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