Thank you for asking your question on JustAnswer. More than likely it is not the picture tube. This model of TV has over 2,000 parts which includes millions of transistors inside the integrated circuits. The capacitors will change value, leak and become defective. Resistors will change value and burn. Diodes and IC can go bad. This may have a domino effect and cause other parts to fail. Replacing one defective part may make the TV operate for a short time but the part will fail again if the parts that caused the failure to begin with are not replaced. The only way to know for sure which parts that are no longer within factory specs and for a proper repair all the electronics must be diagnosed by someone with the correct electronic test equipment specifically designed for TV service and the skills to use the test equipment. I wish I could tell you there was a quick fix or button to push that would fix the TV but that is not the case or the solution needed to get the TV operating correctly. Do you wish to repair this yourself or are you looking for an idea of what the cost to repair the TV will be? If you wish to repair it yourself what type of electronic training do you have? What type of TV test equipment do you own?
Honestly the TV will cost more to repair than the value of the TV. An LCD HDTV will provide a better picture and will cost less to operate. I am sure there are more than one part that is no longer withing factory specs, once repaired the TV can fail again due to it's age. Many parts will no longer be available. You would be best off spending the money on a new TV.