How To: Build your own Composite / S-video > RGB Decoder (HACK)

[segasonicfan1]

To be more specific, this is info on how to repurpose a decoder circuit so you can have regular TV inputs on your favorite arcade cabinet.  Other than the obscure Wells Gardner ones, I don't know where these are available to purchase, so I built my own.

Video:
Pics: http://s18.photobucket.com/user/Segasonicfan/library/CRT%20Mods/Composite%20Decoder%20Hack

Theory:  There are 2 commonly used decoder circuits you can find in older electronics.  The most common is the sharp IR3Y28 and IR3Y29 series of ICs.  These are PURE glorious analog and so they are usually large circuits with many pots for adjustment.  They can be found in Hip Gear LCDs, the PS2 Game Glass, and many other old portable TVs and such.  The circuit I just hacked was the less common TDA8361.  It uses a microcontroller but it also outputs wonderful pure analog RGB signals.

Simply input your own composite / S-video signal following the respective datasheets and pull RGB from the outputs, it's pretty simple.  It gets a little more complicated if you need a C Sync, since these are often configured to only output H+V Sync.  Info on that is over here:
http://www.epanorama.net/circuits/vga2rgbs.html

You also may need a video amplifier in some cases, like the THS7314.  This will depend on your monitor and how strong you need your RGB signals to be.

These are also nice to have if your RGB monitor doesn't have many configuration controls on it for a composite source.  These chips have everything you need for setting levels and are fun to tweak with to get the most out of a non-RGB source.

-Segasonicfan