Have a 27In Gauntlet Dark Legend, converted it over to a NBA Showtime/Blitz. Screen worked fine for a while, though now there is no green color.. It comes and goes. Any sugestion?

First thing I would do is make sure the green signal wire from the game is working, swap the green with the red wire and if the red is working the green wire is fine. If green signal is fine then you probably have a bad transistor on the neck board or it needs to be solder a little because its lose. Probably a bigger transistor with a heat sink on it there is three of them one for each color.