While this sounds like a possible LED issue, that work is for folk with some electrical or electronics background. Since you wrote it was at operator level, this has to be given to the shop for an estimate.
TV has sound from the cable input but the screen is black. The red light (power on) indicator flashes 2 times and stays lit. When operating properly it flashes 1 time an stays off. there is absolutly no display. No channel numbers or remote selections are visible on the screen. The video input cable is connected, but I know from the lack of dispay it is a problem with the divice not the input. I am looking for an operator level troubleshooting procedure to identify and fix any external problems. Also to determine if I need a technican or just a new TV. I was an army auto tech and am able to follow troubleshooting steps, but lack modern electronics knowledge.