How to Make a Fryback!




About: Physicist
Here is an instructable on how to make a fryback, the kind of all flybacks!

Materials needed include:
  • Two large ferrite U cores. TSC international is my favorite place for getting ferrite cores. 
  • Plenty of magnet wire, 28 gauge is preferred.
  • Electrical tape, any color but black. Get the really nice 3M stuff, the cheapo dollar store stuff is crap.
  • Teflon pipe thread tape.
  • Liquid electrical tape.
  • An exacto-knife.
  • Super glue.
  • Regular wire, preferably silicone insulated.
  • Lots of time.

This is mostly a pictorial instructable, because pictures are a lot easier to follow than words.


Step 1: First...

...find a cardboard or PVC tube that fits on your ferrite core. 

Then wrap that tube in about 6 layers of electrical tape, and then proceed to wrap some magnet wire around it.
  • Do not take the magnet wire all the way to the ends of the tube.
  • Don't make the entire winding layer more than a half inch wide. If you do there will be insulation issues.
  • Wrap tightly and make no crossed turns.
After that, put a dab of super glue on there to hold the wires in place. 

Step 2: Second...

...wrap 5 layers of teflon plumber's tape around the coil. This will provide most of the transformer's inter-layer insulation, something critical to prevent it from going up in flames. 5 layers should be good for 4kV, but I personally wouldn't trust it with more than 2.

To calculate your inter-layer voltage, take the output voltage you're aiming for and divide that by the number of layers, then multiply that by 2.

Say I want 30kV and I have 40 layers. (30,000/40)* 2 = 1.5kV inter-layer voltage, not too bad considering I used 4kV worth of teflon. 

Step 3: Third...

...put on one layer of electrical tape, then start winding again.

Secure the wire with super glue, then cut strips of electrical tape and place beside the coil. In the picture there is only one strip (on the left), but two are needed to support the next layer. 

Step 4: Fourth...

...repeat until your brain melts!

I decided to put 40 layers in my fryback, a task that took me 25 hours! Albeit I was watching TV at the same time, but it's still a daunting task. 

Take care to not break the wire coming out of the center! If you do, fun's over. 

Step 5: Fifth...

...solder wires to the magnet wire and glue the ends in place with super glue.

This will prevent you from breaking the fragile magnet wire. I chose to use silicone insulated wire because it absorbs super glue like a sponge, but it's not necessary. 

Step 6: Sixth...

...cover the newly made secondary coil in liquid electrical tape, about 4 coats.

The liquid tape preforms 4 functions:
  • Prevents water from getting in.
  • Prevents the electrical tape from sliding off of the cardboard tube.
  • Adds some insulation.
  • Makes the thing look that much better.

Step 7: Seventh...

...make the primary coil.

This isn't too tricky, all you need is some wire and craft skills to make one. I chose to make a 4+4 turn primary (wires' doubled up so it appears like 8+8).

Step 8: Eighth...

...assemble your fryback!

I used the friction of the paper tubes to hold my cores in place, and when powered up the magnetism clamps the ferrites together. One tip, don't use a metal fastener. It will inductively heat and steal most of your power!

Step 9: Addendum and Video

That's about it! You can power your fryback up with any driver you want, be it a zvs or something else. Remember though, if you attempt to generate too much voltage the fryback will die an untimely death. This is mostly a higher current transformer rather than a higher  voltage one, but nonetheless it sure is impressive.




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    46 Discussions


    2 years ago

    very nice,impressive and informative.thank you.


    5 years ago on Step 9

    Hi is the output of this AC right? however when I make a smaller version of this I only get pulsed DC

    1 reply

    Reply 4 years ago on Introduction

    Probably, but I wouldn't recommend it. You'd have huge energy losses from eddy currents and problems with heat.


    5 years ago

    try it on a half bridge.


    5 years ago on Introduction

    if i want to use this
    but i need realy high voltage

    what must i change?
    i ask this becaus thes looks good enough for my vacuum tube flyback

    Hi nice transformer, I have made a few as well but only a few kV like 4kV.

    I would like to know if you think that shellac soaked card would be a worthy insulator rather than tape for HV?

    2 replies

    It could work, but it won't work well. I'd just invest in a roll of kapton tape; might as well given the time and expense of winding all that wire!


    6 years ago on Introduction

    Hi, could you please post the dimensions of your transformer core , I need to prefer one

    I've found, even when working with 38 AWG wire, that only 2-4 layers of Teflon tape is enough insulation (and, with 26 AWG, it isn't necessary at all).


    Reply 6 years ago on Step 9

    that was smoke from the metal he was using ... its harder to see below a certain point


    7 years ago on Introduction

    Just wondering could you measure the DC resistance of the one you made and post it here?


    7 years ago on Step 3

    After each layer, should I bring the wire back to the beginning of the coil, or can I just continue back and forth?

    1 reply

    7 years ago on Step 9

    nice instructable. it looked like you had either 3 or 4 outputs on the "primary" was one of those a feedback coil? or is this a pure a/c transformer with a centertapped primary? and when you said you doubled up the wire. did you wind two sets of wire on each lil "8 wind" and solder the ends together? also was that regular stranded wire or solid wire used on the primary? could you possibly provide a diagram of exactly how you winded the secondary? was it from left to right and right to left? or did you start over and make a continuous pattern from left to right (as an example) also, what kind of current can you draw from this without destroying it? also what kind of circuitry would i need to just plug this thing into the wall? i know a straight short would not be good so any pointers you could give would be great! feel free to mail me or simply update the instructable a bit! :D