Resistance of various electronic components
What are the effects of damage on different electronic components?
Like living beings, electronic components have a lifespan that depends on their structure, material properties, usage environment, and role within the circuit. Some components may fail due to environmental stress, while others remain stable for years. Just like people, some are more resilient than others, and this resilience is influenced by their design and how they are used.
Imagine winter approaching, bringing cold winds. Some individuals struggle with temperature changes, getting sick easily, while others remain healthy. This analogy shows that failure or damage in electronic components often depends on their internal "constitution" — their quality, design, and durability.
In circuits, not all components are equally vulnerable. The resistance list of electronic components includes resistors, inductors, capacitors, and semiconductor devices such as diodes, transistors, FETs, and ICs. Among these, semiconductor devices are most prone to damage under normal operating conditions.
Therefore, when troubleshooting, it's essential to check semiconductors first. A common failure mode is breakdown, which can be detected using a multimeter’s diode test function. A good semiconductor should show a forward voltage drop of around 0.5V between any two pins. If the reading is significantly higher or lower, it may be faulty.
Much like how scorpions sacrifice their heads during an attack, certain components in a circuit are exposed to greater risks. Components that operate under high voltage, current, or power are more likely to fail. These are usually critical parts of the circuit, and their failure can lead to system-wide issues.
High current generates heat, following Joule’s Law (heat is proportional to the square of current). Components that generate heat, such as high-power resistors or fuses, are considered consumables. Fuses, in particular, are designed to break easily, acting as a safety measure to protect other parts of the circuit. Once blown, they must be replaced.
Damage to components can occur in several ways: overvoltage, overcurrent, or mechanical stress. Overvoltage events, such as lightning strikes, can cause a bridge rectifier to fail. Overcurrent situations, like thermal breakdown in a display tube, can result in physical damage.
Think of overvoltage damage as a sudden, severe injury — like being stabbed, where the body appears intact but internal damage is severe. Components damaged by overvoltage may look fine but will have altered electrical parameters. Overcurrent damage, on the other hand, is more gradual, like being beaten — the component may show signs of overheating, discoloration, cracks, or even burn marks. In extreme cases, the surrounding PCB may turn yellow or black.
When a component looks abnormal, you can perform simple tests using a digital multimeter. For example, testing resistance is straightforward. Diodes can be checked for PN junction voltage drop, while transistors can be tested for normal PN junction behavior. FETs should be checked for body diode functionality and any short circuits between gate and source/drain.
Capacitors, especially electrolytic ones, may show breakdown, leakage, or open circuits. Non-polarized capacitors might short or lose capacitance. Inductors can suffer from open circuits or desoldering. Integrated circuits (ICs) are complex, and even minor internal damage can cause them to malfunction. Testing ICs involves checking the resistance between each pin and ground, comparing it to a known good one. Poor thermal stability can also affect performance, so cooling the IC with alcohol during operation may help identify intermittent failures.
Whether the fault is due to natural wear or human error, it generally falls into three categories: open circuits, component damage, or software issues. Open circuits, like broken wires or poor contacts, are easier to fix. However, component damage — especially without visible signs of burning — is harder to detect. Technicians often rely on instruments to diagnose these issues. Understanding the characteristics of each component is crucial for efficient troubleshooting and maintenance.
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