sometimes it helps to start a new thread with a descriptive title, but we'll see what we can do...

I've got a DE, not a Sega, but I think they are close...

the splash screen - is that the one that says the version # of the ROM's, etc? Or is it a dot matrix fancy title screen?

I'm assuming it's the former. As a little background, there are 2 CPU's controlling the dot matrix. One on the board in the backbox, and one on the DM controller itself. When you turn it on, the DM controller "boots", shows the screen with version #'s, etc.......then it waits for the main CPU to start sending it information.

IF this is what you are seeing, it kind of says "my DMD is booting fine, my power is good, but I'm not getting any signal from the main CPU".

First thing to check? The ribbon cable. Turn your power off. Should be a long computer ribbon cable coming from the mpu to the DMD controller board. Pin 1 on the boards should be marked. Pin 1 on the cable is the one with the red stripe. Disconnect both ends of the cable, carefully align pin 1 on the board with pin 1 on the cable. Push the connectors firmly down on the pins on the mpu and the DMD controller.

75% of the time, this will fix your problem, at least temporarily. If it doesn't, check back and we'll go from there.

couldn't figure out what the heck you guys were talking about until I realized you are replying to a 2 year old posts.

To AKDaddo - this is why I recommended you should start a new thread! The old threads are nice for research, but you deserve a nice shiney new thread to address your problem.