Phil,
You need to call the people in New York who distributes Ketron products. They are Bell Duovox. I would suggest you call Lou Lazaro at 845-268-1001 and explain exactly what you wrote here to AJ. There have been many SD1's experiencing display problems as you have mentioned and I would think Bell Duovox would like to know of your problems and might be able to resolve them for a more reasonable price. Just taking your keyboard to a local service dealer who has perhaps not had many SD1's come back to him, and might not have been aware of the display problems in the past makes me think it is important for you to communicate directly with Bell Duovox in New York. It might be a little more difficult to pack up your SD1 and ship it to New York, but it might save you a lot of money.
George Kaye
kaye's Music Scene
Reseda, California
You can email Lou at BellSolton@aol.com