A capacitor, also known as a condenser or condensator, is an electronic component that stores electrical energy.
When electric current is applied to a capacitor in a circuit, energy begins to accumulate on the capacitor plate. The capacitor is fully charged when the capacitor plate cannot accept any more charge. When the circuit demands this stored energy, the capacitor begins to discharge.
Like any other electronic component, capacitors are extremely sensitive to voltage spikes. Voltage fluctuations can permanently damage capacitors and cause them to fail.
Electrolytic capacitor and ceramic capacitor are the two main types of capacitors. The electrolytic capacitor contains an ionic liquid. Ceramic capacitors, on the other hand, have a thin ceramic layer as the dielectric medium.
Electrolytic capacitors become unable to hold a charge due to excessive current discharge in a short time or drying out over time. Ceramic capacitors usually fail due to interlayer leakage.
There are different methods to test if a capacitor has failed.
When capacitors begin to fail, they often swell, crack, discolor, or begin to leak. Therefore, visually inspecting a capacitor is the easiest way to detect the fault. Even if the capacitor looks flawless, it could be faulty.
Method 1
The fastest and most accurate way to test a capacitor is to use a digital multimeter with a capacitance meter feature. Most mid-range and high-end multimeters have this function.
To test the capacitor, it is necessary to disconnect it from the circuit board. The multimeter button is placed in capacitance measurement mode (symbol with two vertical lines or letter F). Multimeter probes are connected to the terminals of the capacitor, paying attention to polarity. The capacitance read on the multimeter screen is compared with the capacitance (farad F, microfarad µF) value on the capacitor. The capacitor can be considered a good capacitor if the multimeter readings are close to the values indicated on the capacitor. If there is a large difference between the measured value and the actual value or if the measured value is zero, the capacitor is faulty and must be replaced.
Method 2
The vast majority of entry-level multimeters do not have a capacitance measurement feature. Even if the multimeter does not have a capacitance meter feature, it is possible to test the capacitor and distinguish between good and bad capacitors.
Similarly, in this method, it is necessary to remove the capacitor from the circuit board to test it. A digital multimeter is set to measure resistance (ohms). Multimeter probes are connected to the ends of the capacitor, paying attention to the polarity. A slowly rising resistance reading is shown on the multimeter display, and after a short time infinite resistance, meaning an open circuit, is displayed. This test is repeated several times and the resistance readings are noted. A good capacitor shows similar results on every try. If a constant resistance is read in subsequent tests, the capacitor is faulty.
Extreme care must be taken when testing capacitors. If the capacitor is not discharged before testing, touching its terminals may result in electric shock. High power rating resistors called discharge resistors are used to discharge the capacitor. It is also possible to discharge the capacitor by touching a screwdriver between the capacitor terminals. Since this is a dangerous procedure, it should be used as a last resort and should be done with care.
Capacitors are inside many electrical devices and perform various functions. Failure of one or more of the capacitors will cause the circuit board to fail. There are many ways to test capacitors, including the methods mentioned here. The procedures shared here are the most effective.
