55ls4500 - vertical colored lines

[buytamil]

When I switch on the TV, power led blinks twice and see these colored lines. It doesn't go away. I bought a replacement t-con board (6870C-0421A) and installed and still the same issue. Gently taping doesnt change anything. Do I need to replace the ribbon cables ?

 

[buytamil]

any steps to identify the issue ?