complete DUO S-Video mod

[Tatsujin]

does someone know a guide for a complete s-video modification of the DUO?

i allready collected some pieces of information (rgb to s-video converter IC etc..) but never found a complete mod from the scratch to its working end.

here my researches about the CXA1645P IC with NTSC-circuit >  http://www.gamesx.com/rgbadd/cxa1645.pdf
do i need a TTL converter for the Pin 10? from where i will take the external clock?

thx in advance

tatsu

[herr-g]

I've never seen a complete guide and doubt it even exists for public.
As the PCE's video processor has no output for croma and luma you'll have to use a RGB => SVideo IC (like the one you ment above).

I know D-Lite has done it before (with the help of matt from gamesx) and even modded some PCEs for forum members. I suggest contacting D-Lite if he can hand you out a draft.
If you're gonna build it by yourself it would be great to publish it to Lawrence for the public.

Rgds
 herr-g

Btw. It's a damn mess that RGB is still such an alien in all those NTSC regions.

[grahf]

Tatsujin, you need an LM1881 sync seperator IC to get an imput for pin10. http://www.selectronic.fr/includes_selectronic/pdf/NS/LM1881.pdf
You then feed the composite video signal from the duo into that.

I already built my own circuit, using a smd cxa1645. However, I did not finish it. I still need to input the sine wave to pin 6. I could not find any solid information on what type of oscillator I needed to use, or how to use a crystal. I found a digital IC that is supposed to be a replacement for oscillators, but havnt tried it yet.

In any case, a writeup of this would not be hard. The hardest part is finding the cxa1645s in dip package.

[grahf]

I finally finished my CXA1645 based chroma encoder. I managed to squeeze the entire thing into a 4.5cm square project board. Video quality is EXCELLENT compared to the original composite video.

[Tatsujin]

wow, thx a lot for the pics grahf that's awesome!! may you have a complete shematic of your device to share?

[GUTS]

That's awesome, you should post that on Gamesx and get it added to their mods.

[Mortis]

That is indeed swell Boy do I wish I'd be able to see the difference in picture quality!

[Tatsujin]

it's almost like a RGB signal, but not that clear in matter of contrast and colors. but nearly almost.

[grahf]

I dont really have a schematic, I just worked off of the cxa1645 datasheet. I could have built it a lot easier If i used a bigger board.  If anyone has any questions about building their own, check aout the datasheet first, then feel free to ask.

[Michael Helgeson]

Looks really good. If you decide to ever do another,do a step by step guide for building the encoder on here for people. Alot of people have problems with reading schematics but can go off of visual guides perfectly fine.

[grahf]

Thanks for the compliments guys. I just wish everyone could get to see a PCE with decent video   If only I knew where to get the CXA1645s in dip package (the bigger, through-hole ones). These surface mount ones are really hard to work with. On the sdm chip there are two pins of the chip for every hole on the project board. I just split each hole into two with a razor knife. Then removed the contacts on the next row to give myself some room. Also, I tried to arrange everthing so that it was small, and didnt use many jumper wires. If you dont care about this, it will make things easier.

I was thinking about just getting a custom PCB made if I decide to build another one. In the mean time, I may draw up some pictures that better explain what components have to go where on this encoder for those interested in tackling this as a project.

[kspiff]

To whoever eventually makes a schematic of this: you are my hero.

So is this mod pretty much as simple as providing the needed inputs as directed on the datasheet (not including the input from the crystal), then routing the output?  If so I may have to try this out.

I wonder if there would be room for the s-video mod, a region mod, and composite output (RCA) in a regular old US Turbo Grafx-16?  I guess I could always remove the RF modulator and some of the casing/shielding...

[grahf]

I'll start drawing up a simplistic schematic in paint shop when I have time. Its not really hard to build, but people without experience in reading datasheets might have a hard time knowing what type of components to use and such. I'll see if I can clear some things up.

[kspiff]

Any help you can offer would be appreciated.  In the meantime I'll try to figure things out myself and will make a schematic of my own.  If I can figure most of it out maybe you can look it over and help me make some corrections instead of having to make a schematic yourself.

And if anyone else is interested I made an offer of $13.95 for a CXA1645M from a seller on eBay (the only guy who is selling these chips right now) and he accepted, so if anyone else wants to try the same thing you can probably get the chip for $20 even shipped.

[GUTS]

That would be awesome, I was going to pay someone to do mine but Mike said it was a pain in the ass to do Duos so I'd actually like to try and build one myself as a challenge, the only thing I need is some instructions.