LG47LX9900 suddenly can’t see channels on coax aerial, displays “no signal”. Tried another tv on same aerial cable and it work ok.

SOURCE: Sharp LC-52D62U HDTV won't tune-in channel 21.

I finally got Sharp to repair the TV. It was under warenty but they said if the problem wasn't with the TV they were going to charge me for the service call. I told them I wanted a new TV. They sent the tech instead of a new TV. He replaced the turner card and it worked!! Now I get all the channels as well as channel 21.

SOURCE: When in Antenna mode (DTV from the Aerial) some channels do not tune in....

I found I needed at least 80 percent.

SOURCE: Suddenly the Tuner mode reports "No Signal"

Just a solution.

I attached a video recorder., and selected the video channel.
I was able then to see the channels through another AV slot extension.
Then I reset the TV to factory settings.
Samsung full HD reset code is 0000.
I used the original remote control.
I pressed the button TV/DTV to switch between mode., and from the menu I started
the option to scan the channels automatically.
Because the VCR was still connected it looks like it was forced to admit the channels.
I turned off the VCR and click on the TV the remote control for a known channel ( alternative control used) and surprise ... The TV started to react according to expected.
I disconnected then physically the cabling from the VCR and plugged in directly on back on the
wall connector. All is ok.
What was the reason ?
My wife dropped the alternative remote control ( not the original one) on the floor, and apparently an strange code was sent to the TV., which suddenly displayed " No signal".
I hope this can work for you.

Kind regards
Sanchez

SOURCE: digital - Weak or no signal digital coax when hdmi dvd player on

if u have placed your DVD next to your tv ... just maintain distance between then and check out

SOURCE: on a Daytek 46 in LCD TV, no AV Digital Cable Signal, but HDMI OK

Had the same problem.
Fixed by unplugging everything from the power source, leaving for 2 minutes then plugging back in.
Works fine now.