Black Screen

My screen goes completely black after a few minutes of being on. Here are some specifics: It happens on all the inputs and with a variety of sources. IF allowed to cool down (rest?) the images come back then the problem reoccurs at about the same time. It almost feels like a warmup issue. Here is the real issue. I live about 100 miles from a city. I can do alot with repair of electronics due to that very fact of being so far away, but in this area i do not know where to start. I would probably not mind buying a service manual but if the thing is irrepairable, id rather not and just sell it for parts. Ok thanks and i look forward to hearing from ya'll. Reuben