How to monitor the damage of capacitors in the DC screen control cabinet

The following are some methods for

 monitoring the damage of capacitors in the DC screen control cabinet:

1. **Appearance Inspection**:

    - **Check the Housing**: Examine whether there are obvious deformations, burn marks, swellings, bulges, etc.

 on the capacitor housing. If an electrolytic capacitor has a bulge, it usually means that the internal pressure has 

increased, and the capacitor may be damaged.

    - **Check the Marking**: Confirm whether the marking of the capacitor is clear. If the marking is blurred or lost,

it is possible that the capacitor has experienced abnormal conditions and further inspection is required.

    - **Check for Leakage**: Pay attention to whether there are any leakage traces on the surface of the capacitor.

 Leakage will lead to a decrease in the performance of the capacitor or even failure.

2. **Measurement with a Multimeter**:

    - **Resistance Mode**: Set the multimeter to the resistance range. After ensuring that the capacitor is fully 

discharged, connect the probes of the multimeter to the capacitor terminals (positive to positive, negative to 

negative). If the capacitor is normal, a digital multimeter will first display a value and then immediately return to 

OL (open line) or infinity "∞"; an analog multimeter will initially show a low resistance and then gradually increase

 to infinity. If the reading does not conform to the above situation, it indicates that the capacitor may be damaged.

    - **Capacitance Mode**: If the multimeter has a capacitance measurement function, turn its knob to the 

capacitance mode. After removing the capacitor from the circuit board and discharging it, connect the capacitor

 terminals to the leads of the multimeter (red to the positive terminal, black to the negative terminal) and read the 

capacitance value. If the reading differs significantly from the nominal value of the capacitor (beyond the tolerance

 range of ±10% or ±20%), it indicates that there may be a problem with the capacitor.

3. **Detection with an Oscilloscope**: Connect the probes of the oscilloscope to the positive and negative poles of

 the capacitor respectively, and start the oscilloscope to observe the waveform on the screen. If the waveform shows

 abnormal conditions such as oscillation and distortion, or if abnormalities are found when using the phase function 

of the oscilloscope to detect the charging and discharging process of the capacitor, it indicates that there may be a 

problem with the capacitor.

YouTube：https://youtube.com/shorts/_42d9GRiNQY

4. **Detection with a Power Tester**: Connect the output port of the power tester to one terminal of the capacitor, 

start the power tester, and observe the voltage value at the output port. If the voltage value is abnormally low or 

fluctuates greatly, it indicates that there may be a fault with the capacitor.

5. **Measurement of the Time Constant**: Given the capacitance value of the capacitor (in microfarads printed on

 the capacitor), the quality of the capacitor can be judged by measuring the time constant. Connect a resistor with

 a known resistance value in series with the capacitor, apply a known power supply voltage, measure the time required

 for the capacitor to charge to approximately 63.2% of the applied voltage, calculate the capacitance value according 

to the time constant formula τ = R x C, and compare it with the value printed on the capacitor. If there is a large 

difference, the capacitor may be damaged. It is also possible to measure the time required for the capacitor to 

discharge to about 36.8% of the peak voltage to calculate the capacitance value for judgment.

6. **Testing through the Continuity Test Mode**: Set the multimeter to the continuity test mode, disconnect the power 

supply and remove the capacitor from the circuit board. After fully discharging it with a resistor, connect the positive

 probe of the multimeter to the anode of the capacitor and the common (black) probe to the negative terminal. If the

 multimeter shows signs of normal conduction (beeping sound or LED light) and suddenly stops showing OL (open circuit)

, it indicates that the capacitor is in good condition; if there is no conduction indication, it means that the capacitor is

 open-circuited; if the LED light is on and emits a continuous beeping sound, then the capacitor is short-circuited.

7. **Detection with Professional Instruments**: For example, use an LCR meter, which can more accurately test the 

parameters of the capacitor, including the capacitance value, inductance value, and resistance value. Connect the 

two leads of the capacitor to the test leads of the LCR meter and read the capacitance value. If it differs significantly

from the nominal value, it can be determined that the capacitor is damaged.