Unless you are a better tech and have better tools and have better info than that Sony tech i don't think you can do anything yourself.
In such cases, usually repair is just replacing the broken parts. So it seems he replaced the wrong parts or not enough parts. You didn't pay for that, I assume?
Hi, I have a SONY KDL 55EX710.
We moved the TV to another house and now it has an image failure, the 20% of the screen, on the left side, is totally WHITE, and the colors are shiny.
A Sony service wasked 1.300 € to repair it!!
Any solution to repair by my own?
The firmware is updated and I cleaned the connections on the rear panel.
Thank you so much!