I've been trying to get my Cobra Command boardset (Bega's Battle conversion) up and running. I have no official wiring harness, so I've been making my own wiring + PCB adapters, including power, serial, and RGB video. When I tried powering up Cobra Command and plugging it into Dexter I got nothing.
So I did what anyone who loves tedious troubleshooting work would do. I sniffed the 6502 CPU to see where the program was getting stuck.
I found that the program was looping endlessly at a subroutine at 0xE176:
The game is communicating at 1200 bps! I've never seen a game communicate this slowly to the laserdisc player!