Step 2: Wind the transformer
1. take about 1.5-2 meters of copper wire, bend it in half and wind the coil with it. in this case it took around 50-60 windings arranged in two layers.
2. after the winding is done - cut the double end, so that you have 4 loose single tips.
3. clean the tips from the isolation lacquer with sanding paper
4. with a multimeter set on conductivity test, find two separate windings
5. twist two opposing ends of different windings into one contact
6. pre-solder the tips of the transformer.
your transformer is ready!