SMG - TV Displays "No Signal" or "Weak Signal" Error Message
Turn on the external device.
Confirm that the external device is turned on.
Confirm the right source is being used.
Be sure to check the TV source, as well as the source of the external device. Some devices such as cable boxes and home theater systems have multiple sources.
Check the cable connections.
Check that the connections are secure and connected to the correct ports.
Replace the connection cable with a new cable.
If the issue is resolved, the original cable is defective.
Test a different external device on the same source.
If the new device works, the issue is with the original device. Contact the manufacturer of the original device for further assistance.
If both devices do not work, and all other steps have been completed, the TV requires service.