No display on Sony Ericsson Z520i

@stanislavaz2584 since your phone is functioning properly in all other aspects, I would definitely go with a new display. Of course, there is always a possibility that this is board related, but you have to rule out a bad display first. It is also possible that this is a flex cable issue. You will need to disassemble it to look at those things a bit closer. Take a look on here for hints about the disassembly.

I am slightly surprised by your question. After all, in your previous answers you have shown some deep knowledge about SE phones. This should be a simple one for you.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!