Here's a draft pdf of my latest Sega SC-3000 component video daughterboard design. It performs just as well as the previous one, but it is a lot simpler.
http://www.sc3000-multicart.com/downloa ... EagleD.pdf
Main changes are:
1. I got rid of the THS7314/7316. If you did not have to get rid of the R-Y and B-Y back porch pulses then this would be awesome (eg. for a TMS9928A). But it just complicated things once I had to get rid of the back porch pulses. Also it requires a 5v supply which means soldering a supply wire from the SC-3000 motherboard.
2. Uses 3 x AD828 op amps
3. It averages R-Y and B-Y together to give Vnocolor and get rid of the pulses in the back porch / burst interval area of the R-Y and B-Y signals instead of the sample / hold technique of my earlier schematic. This works because the pulses have the same amplitude but opposite phase. Same end result as the sample hold circuit approach - this is just a different solution to the same problem.
4. DC coupled input and output. You could easily add 47uF or larger capacitors to the output if you want, but the DC range should be reasonable at the TV so I haven't bothered. The input MUST be DC coupled for the averaging to work without a DC restore.
5. The first circuit required you to solder a +5v feed from the Sega SC-3000 motherboard. This one runs directly off the horrible 10V +/- 1v input with 100Hz ripple feed from the unregulated 9v Sega power brick (that is what is passed to the daughterboard connector by the motherboard). That 2v / 100Hz ripple sounds awful, but if you think about it the supply voltage only changes a tiny fraction across a single horizontal line scan, so it seems to be well within the capability of the AD828 to adjust.
This gives beautiful output on both my 32" Bauhaus LCD and my 29" Panasonic CRT TV. Stunningly good (well, for a 16 colour palette anyway). I never knew the Sega SC-3000 games looked that good
![Smile :)](./images/smilies/icon_smile.gif)
I will tidy up the schematic and draw up a PCB for it when I get some spare time.
Note: Your TV has to support a 288p (progressive scan) signal rather than a standard 576i (interlaced) signal for this to work over component. But if your TV works over the standard composite AV input with a Sega SC-3000 then there is a good chance it will also work over component. However like anything your mileage may vary. One of my TVs has two component inputs. It supports 288p on one component input but not on the second component input.
Cheers