Good Capacitor, Bulged Capacitor: Visual Comparison

Nix McRetro // 5th April 2013 // Repairs, YouTube

Here’s a useful visual comparison between a brand-new electrolytic capacitor and one that has failed badly enough to bulge at the top.

A swollen or opened pressure vent is an obvious warning sign.

The internal pressure of an aluminium electrolytic capacitor can rise under abnormal electrical or thermal conditions, causing the safety vent to deform or open.

One important catch:

a capacitor does not have to bulge before it is bad.

Electrolytics can lose capacitance, develop excessive losses or leakage, or dry out without presenting such a wonderfully obvious visual clue.

So the damaged capacitor in this video is an easy diagnosis.

The innocent-looking ones can be considerably more annoying.

Sources

Nippon Chemi-Con - Precautions and Guidelines for Aluminium Electrolytic Capacitors - manufacturer guidance covering electrical degradation, leakage and pressure-vent operation.

AI-assisted revision: This post was reviewed and edited with OpenAI GPT-5.6 Sol on 29 September 2026 for fact-checking, sourcing, and editorial cleanup. Final editorial responsibility remains with the author.