RGB NES Jamma adapter

[Drakon]

This project is a commission. This's an av famicom using the rgb ppu chip from a playchoice 10. This system has been modded to include true rgb, s-video, stereo sound with bass boost, powerpak compatibility, and I built an adapter that lets you play this system on a jamma arcade machine connecting through regular ports.

 

[Ashen]

I love your mods man, picture looks lovely on that TV.

 

[Drakon]

I love your mods man, picture looks lovely on that TV.

I feel the same way about your mods! It does look lovely I just wish I had a way to fix the video ringing. Anyway the client is so impressed with this that he's commissioning me to build the same thing for a turboduo. So I guess that's the next thing I'll end up posting.

Also here's some interesting things I discovered while building this. 1: Arcade rgb levels are around 4x the strength of scart rgb. So I had to come up with a rgb amp circuit to take the rgb from the cxa2075 circuit and make it strong enough for my arcade setup. Here's how the image looks without the amp:

With the amp:

And the schematic of the amp I built:

Also for audio these systems I build include a switch to go between stereo and mono sound. Since jamma is mono when it was switched to stereo the audio would buzz because of mixing both channels together straight. I added a 10k ohm resistor to each channel and then they mixed perfectly.

 

[nuke]

This is awesome.

 

[public-pervert]

This is really awesome!