TV has sound no picture

I have a Panasonic vierra tx-37lzd81 lcd tv my wife was watching the tv next minute there was sound but no picture,I’ve turned it on & off thats fine the green light comes on too after about 10 flashes[maybe a few more as very fast] still no picture any idea’s please? with the back cover off there’s a white light on the rear of the screen..I was told it could be the TCON board so changed that still the same great sound no picture