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How can i tell if a transformer is a dc or ac? Answered


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12 years ago

By themselves, all transformers are AC devices by their very nature (AC in -> AC out.)

If it's a wallwart or similar power source that includes other circuitry, such as a rectifier, filter capacitors, voltage regulator, etc., then it's probably DC output.

The best way to tell for sure is to use a VOM (volt-ohm meter), and test it for both DC and AC voltages.