Jamma differences

[TuZhao]

Hi all,
I just put my hands on the Raiden DX board and, surprisingly enough, it doesn't work on my setup that I use for Raiden. How come that Raiden runs great, and on the same setup with the same voltages and cables (I just swap the boards) the only thing I get from Raiden DX is a rolling series of small colored squares?
The only thing that makes sense is that when I ground the COIN wire I hear the typical sound for the inserted coin. But then again, I'm not able to start the game with any of the START wires, nor I can hear the demo sound (the dipswitches are ok).
Maybe the demo is not starting because the game is displaying some warning or such, which I can't see.
Does anyone know something about Raiden DX? I never saw it in the arcades so I don't know its "boot sequence".
One clue about the video is that my TV keeps displaying the "AV1 input" on the OSD, when I see the colored garbage on the screen. Usually that writing is NOT displayed when the video signal is present on the SCART.
So should I assume that Raiden DX uses a very different video signal scheme than that of Raiden? And the TV is not getting the sync correctly?
How can I tell if the board maybe got damaged in the shipping (Germany -> Italy)?

Thanks for any help!