My philips 240b powervision tv, about 10 years old, while watching, all of a sudden the screen video turned into slanting horizontal whilte lines. the input is from setup box. I guess it happened when i was tying to put the volume down from setup box remote.

Slanting horizontal lines indicate that the horizontal hold is out of adjustment. As the components age they change values and don't have the same effect on the circuit. some units have a horizontal hold adjustment pot on the back that can be adjusted to bring the horizontal back to the middle. If the adjustment pot is not on the back the only way to bring the horizontal hold back is on the inside of the unit and this is not a safe proceedure. If the picture was really good before it went bad then it might be worth the cost of repair. If the picture was getting weak (light colors, washed out look) then the repairs are not cost effective (not worth the money to have the unit repaired) There are some tv repair people that work quite a bit cheaper than others. It would be worth a few phone calls to get an estimate and make an informed purchasing decision.