The Ceramic Disc Capacitor Leakage Testing Secrets

Typical values of ceramic disc capacitor

The ceramic capacitor leakage quite often happened when there is a high voltage applied into it. Under normal testing with a digital capacitance meter or an analog meter will not revealed any symptoms and you may think that the ceramic capacitor that you checked is ok. If you skip that capacitor, the chances for you to repair the equipment are very slim.  In computer monitor, the ceramic disc capacitor and high voltage resin coated type is frequently found in the power supply, high voltage and cathode ray tube monitor area. When it fails, it can cause erratic or intermittent problem to the monitor such as blinking display, no display, missing one of the color bar and etc.

Resin coated ceramic disc capacitors

Using analog and digital capacitance meter won’t accurately test the ceramic capacitor failure even out of circuit. A ceramic capacitor leakage in electronic board can pull down the voltage and cause a lot of intermittent problem to the equipment. I will explain to you my true life experienced about this type of capacitor. In computer monitor crt board, the screen line (G2) has about 200 to 600 volt. The ceramic capacitor in the screen voltage line is usually rated at 102, 103, and 472 and voltage rating of 1kilovolt to 2 kilovolt. If this ceramic capacitor dielectric breakdown, it can pull down the screen voltage to a very low level and causing no display or picture. There is no way for an ohmmeter with 12v output and a digital capacitance with 3v output to accurately check the ceramic disk capacitor that have the voltage rating of 1-2 kilovolt or even 3 kilo volt in certain types of circuit such as the inverter circuit in LCD monitor.

So the right way to check the ceramic capacitor leakage is to use an insulation tester. If you have the analog insulation tester or meter, the meter panel will show a short circuit when certain voltage are applied to check the ceramic capacitor dielectrics or materials. The voltages that you can select is depends on the brand or model you had. Some have the range of 50v to 1000v and some have the range from 100v to 5000v. It is optional whether you should have one.

If you have one then it would be an added advantage to you. The other option that you have is to direct replace the suspected failure ceramic capacitor. In my country, you can get a new one in less than RM500 or you may bid a used unit from eBay. Sometimes you don’t need any meter to test the ceramic disc capacitor because the burnt marked in its coating already proven it has gone through some serious heat or high temperature and need to be change.  

A Kyoritsu Insulation Tester

You may also sometimes see cracking in its body. Ceramic capacitor does not have polarity and when you need a replacement; get the exact or higher voltage rating with the same capacitance value.

To test the small blue resin coated ceramic disc capacitor that have the capacitor marking of 104 50v, besides using digital capacitance tester to check for the capacitance value, I also use an analogue meter. Set to times 10Kohm range that has 12 volt output from the probes to check this type of ceramic capacitor failure. Many times it will reveal the bad intermittent capacitors. You will be shocked to see the digital capacitance meter tested ok when checking the capacitor but show a shorted reading when check with an analog meter.

In the market there is certain brand of analog meter that have the range of 100kohm. If you remove the cover, you can't see the 9 volt battery in it, what you see is only the 2 pieces of 1.5 volt batteries. This type of meter can't accurately detect the ceramic capacitor leakage because the output voltage is only 3 volt!

Ceramic capacitor manufacturer produced many construction and types of capacitors, and if the ceramic disc capacitor always failed even though you had replaced a new one then try another type which is the resin coated ceramic disk capacitor.  Replacing a higher voltage rating than the original one may also help to prolong the life of the ceramic capacitor.