Capacitor electrolytic blown

Blown electrolytic capacitor: common causes, symptoms in circuits, and how to prevent failures in electronic equipment.

About this subject

A blown electrolytic capacitor is a common failure on printed circuit boards, especially in power supplies and high-voltage circuits. These components, characterized by their cylindrical shape and aluminum casing, store energy electrostatically through a liquid or gel electrolyte. When subjected to adverse conditions such as overvoltage, reverse polarity, excessive temperature, or natural aging, the electrolyte can heat up, generate gases, and increase internal pressure until the safety vent or casing ruptures, resulting in leakage, deformation, or explosion.

Symptoms of a blown electrolytic capacitor include bulging on the top (cross-shaped or swollen), leakage of brown or yellowish fluid, a characteristic fishy or ammonia-like odor, and in advanced stages, short circuits or excessive noise in the circuit. In equipment such as computers, switched-mode power supplies, monitors, and amplifiers, a damaged capacitor can cause instability, sudden shutdowns, abnormal heating, or total failure.

Main causes include: use of low-quality capacitors with inadequate temperature tolerance, insufficient voltage rating for the circuit, operation in hot environments without proper ventilation, and voltage spikes on the mains. The so-called "capacitor plague" occurred in the early 2000s when manufacturers adulterated the electrolyte, reducing lifespan to a few months.

To prevent failures, it is recommended to use reliable brands (such as Rubycon, Nichicon, Panasonic), respect voltage and temperature specifications (105°C is standard for longevity), replace capacitors in equipment older than 10 years, and install surge protection. Preventive replacement in PC and server power supplies is common practice in advanced maintenance.

Frequently Asked Questions

What causes an electrolytic capacitor to blow?

Common causes are overvoltage, reverse polarity, excessive heat, natural aging, and defective manufacturing (as in the 'capacitor plague' of the early 2000s).

How can I identify a blown electrolytic capacitor?

Visual signs include bulging top (convex surface or ruptured vent), leakage of brown/yellowish fluid, and a fishy or ammonia smell. In operation, it may cause noise, instability, or circuit failure.

Can I replace a blown electrolytic capacitor with a different value?

No. Replace with the same capacitance (μF) and a voltage rating equal or higher (never lower). Temperature rating should be equal or higher (e.g., 105°C can replace 85°C).