LG 75UK6500PTB.AAU tv, no picture

A few small vertical lines were located on bottom left corner of the screen, so removed power source/stands/rear cover/speakers. Checked a few connectors & timing control board, each time I was also returning to view the front of the TV screen checking for signs of improvements. Lines were  disappearing with just a couple left so on the last task I checked some yellow wiring and TAB bonds at the back of the tv. Checked the tv screen  no vertical lines just perfectly clear,  but now there is no 'on screen display'....please let me know what I need to do to have this issue finalized I would greatly appreciate it