Step down the voltage of Mains AC 127VAC to 12VAC or so, I try to use a regular transformer, but it distort the signal ( I will be sending a small 100Khz near the zero crossing of each sine wave, and that is the signal I want to keep.

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This is the original project:

https://forum.allaboutcircuits.com/...n-on-a-led-amplify-stage.162725/#post-1434452

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So in this another question;

Members of this nice forum point me; I need a pulse transformer, or a ferrite core one, to keep the signal integrity.

So I have to make a job and one of my clients donate my an ATX power source, so I disassembly and retrieve the transformers, and the fer rite inductors, the biggest one is the one I foccus on;

This is the ATX before remove the components.

This is the small, yet the bigger transformer I can remove from the supply, I was hoping this has a 10:1 relation or so, but my measurement differ;

So, they are the inductances and the resitance of the coils, I think It 5296uH and simetrical coils to a common tap o the rigth. ( I messure from the center tap, the bigger wire in the middle, to each of the pins on the transformer)

Sadly I calculate the reactance of the primary winding and I get 1.99Ohm at 60Hz.

So I got this questions;

This small reactance on the 60Hz intended frequency of use, means I can not power this device over the 127VAC that I was needing.

Even If I try to use one of the taps at 198uH I got a Reactance of 74.97Ohm at 60Hz.

Are my calculations correct?

After I calculate the reactance, I just use the formula I = V/R to estimate the Amperage on the primary coil correct?

Since I can use this transformer directly and I just need it for signal ( 100mA or so) would be possible to add some resistor divider to attenuate the mains voltage, still getting the response?

If this is not feasible, I can try to re-wind this core, it has 11 x 11mm at the core, I get this simplificated formula of "Ampletos" site, they use the 42 as constant, I dont know from were yet.

The site: http://www.videorockola.com/tutoriales/como-calcular-el-transformador-para-su-amplificador/

Can please verify this?:

I got the core area;

1.1cm x 1.1cm = 1.21cm2.

Square the core area gives the maxium aviable power; (Ampletos assumption)

1.21 x 1.21 = 1.46Watts.

Number of turns per volt = 42 / core area (Ampletos assumption)

Nt = 42 / 1.46cm2

Nt = 28.76 turns per volt.

Since the smaller diameter wire I got here is 30AWG, I will be using this.

So; primary 127VAC x 28.76 = 3653.42 OMG ------it mus be a joke.

seconday 12VAC x 28.76 = 345.12

The main Idea is to replace the ferrite core, cheap transformer, with a more suitable one, for high frequency, Im aware my calculations may be are wrong due the fact I pull up the formulas from an over simplyfied site, and also I know it may be a comercial transfomer, But this is for me a great learning excercsie, so I like to know more and correct theory and make some practices.

Im a industrial contractor of refrigeration, I work all day with mains voltages of 220 and 480VAC, in a hundred amps ratio, so I know how to keep me safe. Still a newbie on electronics, and far more new in the Analog side.

Thanks for the insights, correction and lectures.

-Alex.