O.k then one thing is for sure is that if the menu is also affected then were not talking about external equipment or wiring , this is internal and from you description the video circuit or its supply voltage is affected .
Again this could be about a broken solder joint if I go by the indications you gave me but for a tv of this age it could also very well be that you got a defective component in that circuit , I`m sure that just about every capacitors inside the tv are out of specs by now and troubleshooting this will not be an easy task and certainly not a DIY type of job .
To have a tech. at home working on this could very well cost you $300+ and you will need to find an older tech. like me so that means some shopping around .
If i may be frank , considering the age of the tv and the fact that you can get a new 50" tv with all the bells and whistles for around or less than $500 .
I would think twice before investing that kind of money into this one , your money would be better invested in anew one but again that is up to you so if you need to find repair shops near you then look at the link below and enter your zip code ;
This will give you a list of NESDA member repair shops in your area.
This list may be limited though and you may find more by simply using the yellow pages or simply google "tv repairs" and the name of your town .
You could give a call to different shops in your area to get an idea of their rates , it pays to shop around.
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