If you like your games to look the best, as myself, you probably already know that VGA is the only true solution for the Dreamcast. VGA-boxes aren't rare at eBay, but the only VGA box to deliver 100% perfect signal, is the original one. Those can be rather expensive these days. Therefore, we want to add an internal VGA port, and attach it directly to the mainboard - it gives the same perfect signal, as the original box, it's much cheaper and most 3rd party VGA-boxes sucks, compared to this solution. Of course, this requires to rip your machine appart, and make cosmetic changes as well.
Most people are already aware of mmmonkey's guide, but his print-schematic seems to contain some errors. E.g. V and H sync have to go through the 150 ohm resistors, as the first thing from the Dreamcast board, and they don't on his print.
Anyway, here's what I've made. I started drawing a schematic myself, which is 100% correct.
The best thing would probably be starting with the board. As the image above says, you'd need these components:
2 x Diodes
2 x 4700 ohm resistor
2 x 150 ohm resistor
3 x 220uF capacitors
The next thing I did, was to solder the first bunch of wires, to the VGA pins, as shown on my drawing. The last thing I did, was to solder the last bunch of wires directly on the back of the Dreamcast motherboard. Ain't no big deal really, but to make it all fit, was more of a challenge. I might have used to big wires for this.
Anyway - I solved the problem, by only keeping the switch on the back of the case. Next, I placed the VGA and Minijack -sockets in the old modem (I never used it anyway)
The results *trada*
Any problems or questions, please feel free to ask ;-)