Here is my Dreamcast Internal HDMI mod. I decided to go with a RGB Scart to hdmi adapter, I know VGA is better resolution, and I initially had a VGA to HDMI adapter installed, but I didn't enjoy how it didn't want to display some of my games. So for better compatability I changed to scart. This is the one I used from Aliexpress. This is the circuit I used, plus I added 220uF capacitors on the RGB lines. I wired to the bottom of the board and routed the wires along the back and up the side. My power wires are a bit long in this pic as I was still prototyping it. Hers is the back with the HDMI connector cutout, and a resolution select button above the AV port. Here it is connected and running Bangai-o. Good times. This was an fairly easy modification, only took an hour or so, and am pleased with the result.