Sorry to hear that the screen went blank again after the Factory Data Reset during the setup. I presume blank as black meaning it seems to be off. Now that it is more clear as to when and what is occurring, I’m afraid that the cause is a hardware malfunctioning. The suggestion is to contact Sony Customer Support and describe for them in as much detail as possible the issue and the steps you have taken so far to correct it.
Just as small footnote, would it be possible for you to execute again the Forced Factory Reset process but this time without ANY CABLE except the mains connected to it. Just to rule out the slightest chance that it could be due to some faulty device/accessory connected to the TV.
