In following video you can see how to make an isolation transformer using two regular 220/12v transformers, and then modified them to work as a single isolation transformer 240v to 240v or 120v to 120v .
Video:
In following video you can see how to make an isolation transformer using two regular 220/12v transformers, and then modified them to work as a single isolation transformer 240v to 240v or 120v to 120v .
Video: