Capacitor electrolytic blown

Blown electrolytic capacitor: common causes, visible signs, and how to prevent failures in electronic components.

About this subject

Electrolytic capacitors are essential components in electronic circuits, used to store electrical charge and smooth voltage fluctuations. They are characterized by high capacitance relative to size and defined polarity (positive and negative terminals). When an electrolytic capacitor "blows," it typically suffers a catastrophic failure due to overvoltage, reverse polarity, electrolyte aging, or excessive heat. The liquid or gel electrolyte may leak, causing corrosion on the circuit board, and internal pressure opens the safety vent at the top (cross-shaped notch) or deforms the aluminum casing. Visible signs include a bulged top, dried electrolyte residue (brownish or yellowish substance), and, in extreme cases, a fully detached cap. These failures are common in power supplies, computer motherboards, and inverters, especially in equipment over five years old or exposed to high heat. Replacement with capacitors of the same capacitance and voltage rating, preferably with longer lifespan (105°C instead of 85°C), is the typical remedy. Prevention involves ensuring adequate ventilation, not exceeding voltage ratings, and verifying correct polarity during assembly.

Frequently Asked Questions

What makes an electrolytic capacitor blow?

Common causes include overvoltage (exceeding rated voltage), reverse polarity, electrolyte aging (loss of capacitance), and overheating. Internal pressure increases and ruptures the safety vent or deforms the casing.

How can I identify a damaged electrolytic capacitor?

Visually, look for a bulged top, electrolyte leakage (brownish or yellowish residue), corrosion on leads or PCB, and in extreme cases, a detached cap. The circuit may exhibit power supply noise or malfunction.

Can I replace a blown capacitor with one of higher capacitance?

Not recommended. Use the same capacitance value and voltage rating equal to or higher (but never lower). Changing capacitance can affect circuit behavior and cause instability.