If you have fuzzy picture on all channels only on ONE tv, the first obvious step is to check all the wires from the outlet to the TV. This is usually the problem.
Next, determine the wiring scheme of your home (Home Run or Loop, or a combination of both).
If you have a junction, determine which line at the splitter feeds the TV you're having problems with. Make sure that the connector on it is in good shape, is screwed onto the splitter properly, etc.
If everything checks out, then the line running from the junction or splitter to the cable outlet may need to be replaced.
If your scheme is Loop, see if any outlets AFTER this outlet has the same problem. If there are outlets AFTER this one, and they look good, then there is either a problem with your TV, a problem with the cables running from the outlet to the TV, or in very rare cases, one of the legs of the splitter may be bad.
If this is the very last outlet in a loop system, you may have just run out of signal. Please read my definition of Loop System and consider running a new line to the FIRST splitter to send more signal that way.
(Read my section on Splitters to understand this better.)
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