It sounds like it has dryjoints(bad solder connections) although components will be changing value after this period of time and the tube will be a bit tired. It should however work if the joints are seen to be going over them with a soldering iron.
As it has been causing problems for some time it my be obvious with a ring around the joint and may even be a bit black.
If difficult to locate you could turn the lights off to see a spark to locate but really shouldn't use the set in this condition or more permanent damage will result.
sparky
November 2005