Bondwell 8 is a nice little portable 8088 computer. It has a LCD screen with grayscale that isn't great for gaming. Since it has Composite and RGB ports I was curious to see if i could connect it to a TV. The composite port did only carry black and white signal so to get colour the RGB port was the only option.
Since the signals are TTL level (5V) it has to be reduced to 700mV. Thes signals are digital and to produce more colors it has an intensity signal that needs to be combined with the RGB data. I made the circuit below to ha this. It is inspired by a design on H2Obsesion. I was a bit lazy so instead of combining hsync and vsync to composite sync I simply used the composite video output. Turns out that it works great!
I cut of a standard Scart cable that i zip tied to a prototype board with the circuit.
I started Pinball Magic in CGA mode and hey we got color!