Capacitors are critical components in all electronic devices, providing filtering, decoupling, timing, and voltage regulation. Over time, capacitors—especially electrolytic capacitors —can degrade or fail entirely. Recognizing the symptoms of failing capacitors is essential for diagnosing and repairing vintage or modern electronics.
Symptom
Description
Common Devices Affected
Bulging or domed tops The capacitor’s top should be flat. Bulging indicates internal gas buildup from dielectric breakdown.
Power supplies, motherboards, CRTs
Leaking electrolyte Brown, tan, or white crust forms around capacitor base or vents. This corrosive fluid damages nearby components and PCB traces.
Analog boards, vintage computers, audio gear
No power / intermittent startup Failed power filter capacitors cause voltage drops or power-up failure.
TVs, amplifiers, game consoles, PCs
High-pitched whining or buzzing Failing capacitors in switching circuits may cause coil whine or unstable oscillation.
Power bricks, CRTs, LCDs
Image distortion / display anomalies In CRTs or LCDs, bad capacitors in video or deflection circuits can cause image ripple, shrinking, or flicker.
Monitors, televisions
Audio distortion or hum Filtering capacitors in amplifiers may leak or dry out, introducing 60Hz hum, buzzing, or reduced volume.
Audio receivers, speakers, synths
Overheating components Failed capacitors cause voltage ripple, making voltage regulators or power ICs run hot.
Any device with power regulation
Reboot loops or crashing Voltage instability causes CPUs or logic systems to behave unpredictably.
Routers, computers, set-top boxes
Vented Electolytic Capacitor Bulging vent on topLeaking fluid at baseDiscolored PCB area Burnt or corroded leads Lifted or cracked casing Usually fail short-circuit
May exhibit smoke, spark, or explosion
Blackened or cracked shell Rarely leak, but can:
Crack due to stress
Short if physically damaged
May show no outward signs but cause logic instability
Method
Tool Required
Notes
Visual inspection None
First and easiest check
ESR testing ESR meter
Low ESR is critical for power filtering
Capacitance measurement Capacitance meter
Must desolder at least one leg
Multimeter continuity test Digital multimeter
Detects shorts or opens in some cases
Always replace failed capacitors with equal or higher voltage rating .
Use 105°C-rated capacitors in power supplies for longevity.
When possible, choose Japanese-brand capacitors (e.g., Nichicon, Rubycon, Panasonic).
Clean the PCB after leakage using isopropyl alcohol and inspect for damaged traces.
Recap entire groups of capacitors together if failures are widespread. Power up vintage gear periodically to help reform capacitors.
Store electronics in cool, dry environments.
Avoid prolonged exposure to heat, dust, or moisture. 
