MY TV PICTURE HAS GONE A LITTLE DARKER AND ADJUSTING BRIGHT, CONTRAST, COLOR,ETC. DOES NOT HELP

How long u have this RCA analoge tv?Around 10 years or more and used it like about 5 or 6 hrs everydays?Yes,than ur tv it is losing CRT tube radiation cohetion.As times go bye years in years out the tv CRT-(tv tube) radiation will slowly dying out,Tv actual pictures will lost some of it luster and it brightnesses to the tv auctual pictures.Brightnesses of CRT tube will get darker and darker until the tv actual pictures barely it is watchable anymore.Contrast,Brightness and Colors adjusting more will help some.But u have to take this tv aparts and take a Flat scerw driver turn up a little bit more of the tv HV-(high voltage) SCREEN button on the FBT-(flyback transformer) to make any big differences of the CRT tube brightnesses.The FBT-(flyback tranformer) is the big block of plastic with a red wire with a black cap hook up to the tv CRT-(tv tube).This adjustment on of the FBT,HV-SCREEN button will help the tv CRT-(tv tube) last another year or two.