I've got a similar problem. I bought an old Nintendo DS and I wanted to repair it. It turned on but randomly turned off. So I opened it, I cleaned all the contacts and I tried to assembly everything. The problem is that now, when I turn on, the green light appears just for a few seconds and the screens are black. How can I check if I broke some cables or the cables are wrongly connected? I noticed that the flat cable of the top screen doesn't "close it" very well... It seems too "loose". Any suggestion?