How to test a Ceramic Cap

bertus

Joined Apr 5, 2008
20,655
Hello,

It is a safety capacitor.
Read this article:
https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/

From the article:
If a Class-Y capacitor, also known as the "line to ground capacitor" or "the line bypass capacitor"—the capacitor placed between line and ground—fails short,
this could lead to a fatal electric shock due to the loss of the ground connection.
Class-Y safety capacitors are designed to fail open.
A failure will cause your electronic device to be subjected to the noise and interference that the capacitor would normally filter out,
but at least there will be no fatal electric shock hazard.

Bertus
 

ronsimpson

Joined Oct 7, 2019
824
A capacitor meter will probably read 2200pF. (more or less)
A ohm meter should read "open".
Meters measure at a very low voltage. This is a high voltage cap and probably should be tested for leaks at 100 volts or more.
Because of all the power parts in this part of the circuit, the caps need to be tested out of circuit. Pull one leg out of the board.
A shorted cap will measure near zero ohms even in circuit.
Often "Y" caps show damage if the are bad. These look good.
If these caps were removed your power supply will still function. So a open cap will not effect your circuit much. A shorted cap will pop the fuse.
 
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