Sony Bravia Black light issue

you probably have to take the set apart a bit... ie get access to the back. Its either a failing backlight element (bulb or LED depending on the model design). BUT once you have access to the back, check / reseat all the connector especially those going from and to the power supply which has the inverts for powering the backlights. Having to replace / repair the backlights can be done but it is usually pretty expensive unless you undertake the "delicate operation" yourself.
 


Thank you, I will open it later today with assistance from a professional in the field. He used to work mostly on CRTs though. This one is an LED, and has been behaving itself since last night. It's odd, this problem is very intermittent - it comes and goes.