As asked you find a repair shop, get a quote and decide if it's worth it.
You may have really wanted to ask if there is a non-technical fix which could be the old unplug it and wait method. Or you wanted someone to guess what part to replace which is what it is, guessing. A tech wants the set on the bench, the service manual and uses these items along with bench gear and their experience to decide what to replace.
At 8 years there are few parts at times so the cheapest fix is usually a new set. That can really upset those that are used to repairing everything.
does anyone have a solution for our problem:
Our Sony bravia (about 8 years old?) a few minutes after turning on, the picture disappears, but the sound remains on?