This is a quick video on how to override the Mega Drive ISA card for PC only mode. By doing this you can troubleshoot issues on the PC side with access to the entire motherboard. I am fairly sure I’ve covered this previously in a post but without accompanying video.
Usually with the Mega Drive ISA card removed, you will get no video at all as the front switch that goes between Mega Drive and PC mode is no longer interfacing with the computer at all as it is on a daughter board that connects into the Mega Drive ISA card and then onto the PC. With the ISA card removed, that interaction is gone and you get no video! So enjoy the video and photos below. And as always there is more in the photo gallery in the menu bar above.