How to Troubleshoot an LG TV for Flickering Lines
1. Reset the LG TV by unplugging the power cord from the outlet into which it is plugged for a full 30 seconds and plugging it back in. Allow the LG TV to fully reboot before powering it back on, and check the picture to see if the lines still appear on the screen.
2. Unplug the audio and video connection cables that attach the device you are trying to watch to the TV and plug them back in. If you are using a DVD player connected via component cables, for instance, unplug all 5 component cables from both the TV and the DVD player and plug them securely back into the TV. Once again, check the picture for any improvement.
3. Scan all of your channels and video inputs in order to determine the scope of the problem. If the flickering lines appear on some or all of your cable TV channels but not on any of your video inputs, your cable TV provider may be experiencing a service outage or degradation and you need to contact its technical support department. If the flickering lines appear on all of your channels and video inputs, the TV will most likely need to be serviced for a failure of its picture components.