What is wrong with my bigscreen TV?!?

Question

we turned it on yesterday, and it had a lot of green in the picture, and looked like the only colors were gray, green and black/white. We can still see the picture, but it is really messed up. The weird thing is, this only happens when its in "cable" mode, when I hook my xbox 360 up to it it is in perfect HD. The TV is about 8 years old and has definately had its use, could the TV just be going bad? we have another cable box in another room, and it doesn't do this, so I don't believe its the cable box.

Answer 1

How is your cable box hooked to your TV?

If they are composite/component cables, check to see that the cables are in the right jacks.

Connecting a composite output to one of the component TV inputs would cause this symptom.

Answer 2

The problem is likely the circuit that splits the incoming TV signal into the different colours for display on the picture tube.

I am presuming that when the TV is in Cable mode, it is getting its signal from the Cable TV connector, the s***w-on plug from the Cable TV company cable.  Inside the TV, once the tuner selects the Cable TV channel, the signal has to be pulled apart into Red Blue and Green signals.  The Red Blue and Green signals are provided to the picture tube.

Now I don't own an xbox, but I am guessing that the output from the xbox is component video, and this is what is being fed to the TV.  The green blue and red RCA input jacks labeled Y Pb Pr need a different type of decoder circuit. I presume the decoder circuit for component video still works, so you still get a proper picture.

Try hooking up an old vcr, etc using the yellow jacks (yellow output on vcr to yellow input on TV).  This is composite video.  Composite Video is the same signal the TV's internal tuner outputs, and so probably uses the same malfunctioning decoder.  If the signal is the same greenish picture, this is likely the problem.

I cannot give more insight without an extensive lecture in Electrical Engineering, so I will leave my educated guess at that.