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Dial-up card's transformer voltage? Answered

Can anyone tell me about the input and output voltages of the transformer found in dial-up card? I saw some project need it but I don't know any info about it

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Jack A Lopez

Best Answer 4 years ago

I think that is an isolation transformer, and it is not made to handle a lot of power. I am also guessing the turns ratio is 1-to-1.

Try pulling it off the modem card. Then measure the DC resistance across each winding. Also inspect the little transformer to see if tell if there is any difference in size of the wire used for each winding. Sometimes the transformer will be so small and tightly wrapped, or entombed in plastic, so there is no way to actually see the wire it was wound with. Other times you'll be able to actually see a little bit of the wire, and it will be obvious; e.g. this winding has thicker, or thinner, wire, or it looks like they're the same thickness.

If you have two windings, with the same resistance, made out of the same gauge (thickness) of wire, it kind of suggests those windings are the same length, and likely the same number of turns.

Of course, the real diagnostic way to test a transformer to find its turns ratio is to apply a small AC signal on one set of windings, then look for that signal on the other winding, for to see if the voltage is bigger, or smaller, etc.

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Mad FoxJack A Lopez

Answer 4 years ago

yeah, thanks. I set my multimeter to measure the resistance, and the ratio is 1:1 just like you said. And how can I measure the winding turns? Does I have to take it apart?

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Jack A LopezMad Fox

Answer 4 years ago

In your question you wrote, "I saw some project need it but I don't know any info about it"

And I am guessing that means you read about some project that needed an audio transformer, but you did not know anything about the part you had, the transformer pulled off this modem card.

As far as the project is concerned, I suggest just trying the part you have to see if it works, or rather to hear if it works, since its probably some kind of audio project.

Trying to discover the actual number of turns on each winding, will be tricky, and probably not all that helpful. I mean not all that valuable to know.