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Electronics Engineering QUESTION #11697
Question 1
Which parameter best identifies a degraded electrolytic capacitor in a switching power supply output filter without desoldering it?
  • Capacitance value with a DMM
  • Leakage current with a power supply
  • Equivalent Series Resistance (ESR) with an in-circuit ESR meter✔️
  • Dielectric absorption with a megohmmeter
Correct Answer Explanation
ESR rises significantly as electrolytic capacitors age or degrade, long before capacitance value changes noticeably. An in-circuit ESR meter can measure ESR at high frequency without removing the component, making it the most practical diagnostic tool. High ESR causes excessive ripple voltage, heating, and SMPS instability.