Electrolytic Capacitor Lifetime and Capacitance Loss After 30 Years Storage

Electrolytic capacitors age over time even when not in use, primarily due to electrolyte degradation, operating voltage proximity to maximum ratings, and temperature conditions. This aging results in reduced capacitance and potential failure modes such as leakage or short circuits, especially in aluminum and tantalum electrolytics. Re-forming capacitors by gradually applying voltage can partially restore capacitance, a technique used in vintage radio restoration. Replacement of all electrolytic capacitors in circuits older than 25-30 years is generally recommended to ensure reliability, as aging capacitors may cause circuit malfunction. Non-polarized capacitors like polyester, mylar, mica, and paper types tend to be more stable but paper capacitors can become leaky over time. Large electrolytic capacitors may initially show abnormal charging behavior and capacitance readings that stabilize after repeated measurements. The Sprague brand is noted for high-quality capacitors, with some older Sprague 15,000µF capacitors measuring above nominal capacitance after long storage. Tantalum bead capacitors can fail short-circuit after storage, posing risks such as transformer damage. Testing methods include capacitance measurement and simple smell tests for leakage. Overall, proactive replacement or re-forming is advised for long-stored electrolytic capacitors to maintain circuit performance.
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