Thank you so much to all of your answers! They were really great! The one thing I tried a lot is changing the transformer and the connector. But, not with another orginal Casio connector tho. I tried with many other, some that are from other pianos, some that were creater by my father from connectors of computers or scaners, etc. And some from the tech that I went. And with some of them the piano worked, just for a while, and for the other ones it just didn't worked.
I also think that the tech was not that competent and said that just to get free from my piano! That's why I thought to bring my piano to another tech, but every musician from my country told me that "that tech" that I brought before, is the best one in my country. Thing that I'm not really sure! I live on Ecuador and there's no much where I can go to fix it. So I don't really know what to do.
Maybe I should buy another original connector from Casio, and see if that works?
Thank you again for all of your answers, you're great guys!
PS: And yes, Haedo is my fathers surname, and he is from Bs, Argentina!