Intermittent Wired Signal
With the TV connected to an indoor antenna, the picture and sound comes and goes on one or more channels. Depending on the make and model, a message may appear on the screen saying something like "No connection", "Check Your Cable", "Invalid Signal Format" or "Weak Signal".
With the TV connected to an antenna or a set-top box, the picture and sound comes and goes on one or more channels (perhaps more frequently during windy or rainy weather). Depending on the make and model, a message may appear on the screen saying something like "No connection", "Check Your Cable", "Invalid Signal Format" or "Weak Signal".
Disconnect, inspect and reconnect the coaxial cables starting from the TV or set-top box and working your way outward. Loose connections can cause poor signal problems, especially when they are outdoors where rain or moisture can get in and short out the signal. If you find a wet connector, a quick fix may be just to blow forced air into it to displace the water. A better solution would be to replace the connector with a new, dry one. This would require a special tool and a little know-how which you can learn by searching your favorite search engine on the web. The best solution, if you find a loose or weathered coaxial cable connector, is to replace the cable.
Note: Coaxial cables that are exposed to the elements of nature should be of the kind made for exterior use. If you are having to replace the coaxial connectors, these cables are easily identifiable as having a metal foil that is tacky to the touch between the insulation of the center conductor and the ground (earth) return wire.
The picture and sound could have been just fine, but then all of a sudden the picture and sound disappear, and then come back again (regardless of what channel you are watching). Depending on the make and model, a message may appear on the screen saying something like "No connection", "Check Your Cable", "Invalid Signal Format" or "Weak Signal".
First you need to rule out any possibility that the problem is not the TV. If you have a DVD or Blue-ray player connected to your TV, watch a movie and see if the same thing happens. If movies play okay, then the problem is probably not the TV. But if it does happen watching movies, and if you are using an HDMI input for the player, skip to the next paragraph. If you are NOT using an HDMI input for the player, then You'll need to arrange to have a TV service technician come and look at your TV.
To dig further, you will need to know how your TV is hooked up. You may read, How Is My TV Hooked Up? for assistance. What is the name of the input or source displayed on the screen when you watch TV? If it’s the "TV" or "ANT" input, then it will either be 1.) a weak signal coming from your antenna, cable box, or satellite receiver, or 2.) a loose or faulty cable connection somewhere between the TV and the where it goes. Try changing channels. The problem may occur on all channels, some channels, or just a few channels. If you use a set-top box, or if you use an antenna and live in the city where you should expect to have good TV reception, the cause is usually a bad cable connector. If you found that the problem began when the weather was rainy or windy, that’s good clue that the faulty connector is somewhere outside.
If you watch TV using an HDMI input or source, and the DVD or Blue-ray movie played fine, then the causes could be either 1.) a bad cable connection upstream from your set-top box, or 2.) that there is an HDMI incompatibility issue at play between the TV and the set-top box. If it’s a bad cable connection, follow the advice from the previous paragraph. If it’s an HDMI incompatibility issue, this means that your cable or satellite TV service provider has done something to change the software in your set-top box. There may be a software update that can be performed on the TV that will cure the problem. You can read, Updates on how to do that. If the latest software is installed in your TV and you still have the same problem, then you need to contact your cable or satellite TV service provider, because the problem is not with your television.
The picture or sound is intermittent because of a faulty cable connected to the TV, or because of a faulty connector on the TV itself.
Cables can become intermittent or go bad at their connectors. This can happen when the cable is disconnected repeatedly by grabbing it by the cable itself and tugging, rather than grasping the connector to disconnect it. Repeatedly unplugging and plugging in cables can also damage the female connector on the TV causing an intermittent connection as well. To tackle this problem you will need to gain access to the printed circuit board (see How Do I Get To the Circuit Boards in a TV?).
If the connector does not feel loose when you rock it back and forth, but the connection comes and goes, then there is probably a hairline fracture on the printed circuit trace to which the connector is soldered. If this is the case, then the board will either need to be repaired or replaced. It can be repaired by locating the broken trace, scaping the solder-resist off of the trace on either side of the fracture to expose the actual copper trace, and then reinforcing the trace with solder. If the connector feels loose to the touch, then it is likely that the printed circuit board has a crack in it, and will need to be replaced.
The printed circuit board in your TV that would most likely cause these kinds of issues is called the 'Main Board', or 'Signal Board'. It is generally the one that is populated with all those connectors for connecting various devices to the TV that are accessible in back of the TV.
Sometimes the failure could be caused by the actual connectors (jacks) on the printed circuit boards themselves. They can become electrically intermittent due to excessive mechanical stress from either 1.) the wear and tear of constantly plugging and unplugging cables into them, or 2.) the constant physical weight or tension imposed on them by the cable.
Whether the problem is with the board-mounted connectors, or some other component on the Signal Board, the board would definitely need to be replaced, and this web site can show you how to replace it. The articles How Do I Get to the Circuit Boards? and Replacing Circuit Boards in a TV provide useful information.