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Testing Electrolytic Capacitor


electrolytic capacitors

The best way of testing a capacitor will depends to the type of capacitor you are going to test. Electrolytic capacitors that are leaky are not so common. You can take each capacitor out on the circuit and test it using a cap checker or using your VOM, but in-circuit testing of the capacitor is quicker and save a lot of time.

Do a visual observation and inspection to the capacitor and see if there are any electrolytic capacitor are bulging (they are leaky and commonly get hot), or physically leaking (corroded terminals). Next, if the unit will power up, search for indications of an open filter caps, hum bars in the display/picture, hum in audio, flickering displays, low B+ but nothing gets hot, etc.

If you have an noticeable fault, like a lowered vertical scan on a TV set or monitor for example, to locate the capacitor that is starting to open up, you can bridge each of them with another capacitor, one at a time and see if it fixes the problem. (Experience has taught me that bad electrolytics will not -usually- kill vertical sweep completely.) In a TV set that is several years old or more, there could be more than one cap dried out (open). Check them all.

As mentioned before, leaky caps are actually quite rare, but it does happen. Shorted tantalums and electrolytics capacitors in a power supplies can actually explode. Obviously, leaky caps must be taken out from the circuit to replace them for test reasons.

Most of the other types of small capacitors: mylar, disc ceramic, etc. are pretty rugged. It is rare indeed to find them bad. It happens just often enough to keep a tech humble. But I also encounters that this small caps are the culprit, and the problem is that they are get leaky.

Posted by Ronelex 4 Responses

4 Responses to “Testing Electrolytic Capacitor”

  1. lamperd says:

    I’m very old ronelex’s Blog reader. I like maximum Articles. Its great effort of writer. Now i’m going to share a Capacitor , Resistor, Inductance etc calculator, By using Online. pcb calculator is the best calculator for Engineers and Electronics students.

  2. vilas khare says:

    Sir, I am having SONY TV ( Triny Tron 21″ ) and having problem of Stand by condition. Unexpected timely the TV goes in stand by condition with big loud noise. Will you give me advise in which section the fault is created. Some times it works 1/2 hours without any problem and some times problem create within 15,20 minutes. ( I tried to resolder all the pins of vertical IC ) Please Advise.

  3. kassaw says:

    tel me how to know faulty capacitor,transistor,vdr resistor,ic to test with digital multimeter

    • ronelex says:

      set your tester in capacitance range and test if the reading is still on its accepted value reading with its tolerance. You can also try to use and ESR Meter which can be used in circuit :)


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