Thank you, that's a good idea!
By rainbow cable, are you talking about the cable that connects the two boards to each other and juts runs from board to board? That is in place. As for the gray ribbon cables, I don't remember seeing any ribbon cables...could it be it's missing it possibly and...
I hate to hijack this thread or anything, but I'm having a (somewhat) similar problem.
I'm restoring a DK machine and when all the parts I had were first put in, it turned on and worked...briefly...then it stopped working and the screen turned to something like the middle of this monitor...