Do you have reset and clock? Bust out a logic probe and start checking for activity.
Also check continuity on the 5V to the clock from the iron ferrules on the bottom of the board (L12, 13, 14). I had a similar problem on my SE/30 (no video or bong), the issue was that it didn't have clock...
I returned home this evening, reinstalled the logic board into its proper Mac, and all is well. I'm not sure how the ferrule cracked. This SE/30 was stored in its original box in a basement for decades, as it was allegedly barely used before being put back into said box. I doubt the case had...