Sorry to say but the Toroid may be the only re-usable item in that controller unless you have the electronic skills to fault find and replace the defective components.
I don’t know of any ‘Plug n Play’ or EZ replacement controllers they all require some knowledge and skills to connect and set-up. The cheap Chinese controllers / boards offer no customer support and quite often the just don’t work at all and so are best avoided.
Please take a look at the Gecko G540 and have a read of the support information available on their website – this will give you a good idea of what is required and the degree of complexity etc.
https://www.geckodrive.com/g540-4-axis-digital-stepper-drive.htmlThere is much to learn but, as a hobby, the journey is great fun (some tears along the way) and the rewards are more than worth the effort.
Tweakie.