Page 106 - Testing Electronic Components

Testing Ceramic 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 analogue 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 colour bar and etc.

Resin coated ceramic disc capacitors

Using analogue 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 Cathode
ray tube (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

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