- 1). Look for any capacitors showing signs of discoloration or charring. Sometimes a failure is obvious. Look for cold solder joints that may indicate the presence of heat at one time. Use a magnifier and look for any cracked capacitors, a sure sign of failure.
- 2). Test capacitors in the circuit with a multimeter set to measure resistance. Be aware that other current paths may exist on the board, making the multimeter results unreliable. If a capacitor is connected between the gate of a MOSFET and ground, for instance, and the mulitmeter shows a short circuit, either the capacitor or the MOSFET could be bad.
- 3). Remove the capacitor from the circuit to test it. Capacitors are readily removed with thermal tweezers or a hot-air de-soldering hand piece. Test the capacitor with a multimeter set to measure resistance. A good capacitor will test over the limit (OL) of the meter display. Multimeters usually have no more than a few volts on their leads, but capacitors will occasionally break down under higher voltage while testing OK on the multimeter.
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