Mega Drive color encoding

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TulioAdriano
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Mega Drive color encoding

Post by TulioAdriano » Fri Oct 12, 2007 1:51 pm

Allright, I have a Brazilian Mega Drive that gave me most of the unforgetable moments of my life, when I was a teenager.

When I moved to USA, of course I couldn't leave it behind... I can't blame those guys that bring dogs and cats to other countries... I brought two suitcases full of videogames, games and accessories. My whole Sega collection is here.

Yesterday, after 4 months, I finally plugged the Mega Drive in the TV. I was planning to install my Flash Writer so that I can test TRPG Cartridge version (while it doesn't exceed 24 Mega), also to revive my old games.

Surprise, surprise! The TV is not PAL-M compatible. On Brazil most of the TVs are PAL-M, PAL-N and NTSC compatible so all my consoles work great, but it seems that USA industry don't care a lot to South American TV standards (I wonder why... :wink: ) so as a result I got black and white picture. PAL-M frequency is 60 Hz so the picture is not out of sync. Just black and white.

Sad, sad... I have two basic resources: first and easy, buy a Sega Genesis, second and not as easy is mod my MD to output NTSC signal.

Now the question: Is it possible to simple mod my Mega Drive to output NTSC? Will it be cheaper to buy a Genesis?

Thanks.
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Shiru
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Post by Shiru » Fri Oct 12, 2007 2:06 pm

How about RGB mod instead?

TulioAdriano
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Post by TulioAdriano » Fri Oct 12, 2007 2:10 pm

I don't have a spare monitor to use with my Mega Drive. It would be a good idea in that case.

But all I have is a spare 20" CRT TV, perfect for my Mega Drive.

So is it possible?
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Shiru
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Post by Shiru » Fri Oct 12, 2007 2:20 pm

Your TV does not have SCART?

You can build NTSC color encoder which you can connect to SMD through RGB mod. There is many schematics based on different encoder chips. Check AD724 chip, it needs very simply schematic.

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Post by evildragon » Fri Oct 12, 2007 2:20 pm

TulioAdriano wrote:I don't have a spare monitor to use with my Mega Drive. It would be a good idea in that case.

But all I have is a spare 20" CRT TV, perfect for my Mega Drive.

So is it possible?
Do what I do, get the JROK RGB to Component adapter. When I hook up a PAL MegaDrive to it on my TV, it's in full color.

Mainly, it takes RGB, but converts it to Y-Pr-Pb, which doesn't have color encoding like NTSC or PAL, it's the same for every scanrate. And the JROK does both 60Hz and 50Hz. (and some of the TVs here in the US can do 50Hz.. my fathers KLH does)

TulioAdriano
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Post by TulioAdriano » Fri Oct 12, 2007 2:23 pm

The TV is not older than 2001, but it doesn't have anything but an 75 ohm antenna connector and a single (MONO!) AV input (composite video).

So no video component, no SCART.

Any ideas?

Thanks for helping.
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evildragon
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Post by evildragon » Fri Oct 12, 2007 2:30 pm

You can RGB mod the TV. :p

I've done it, it's just a tad dangerous.

(I only did it because I'm building a TV right now, from scratch, to look like a 50's color TV. So I right now fresh in my mind, know how to build a TV, and thus, how to mod one.)

Shiru
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Post by Shiru » Fri Oct 12, 2007 2:41 pm

I already said idea that in case your TV don't have SCART you can build NTSC encoder. You can mod built-in encoder, but I think that more difficult and that destructive way (with external encoder you always can go back to PAL easily).

For example, check this schematic of NTSC/PAL encoder based on AD725 chip. With AD724 it will be even simpler because it can work with oscillator directly (look to datasheet to get idea). There is many other encoder chips, including that ones which used in SMD, but they need bigger schematic.

TulioAdriano
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Post by TulioAdriano » Fri Oct 12, 2007 2:42 pm

I've researched on PAL-M to NTSC converters and those have prices around $300. Considering that Ebay has offers of Genesis at $10 (buy-it-now) it might be a better option to buy a genesis and switch the circuit board (of course I don't want that giant Genesis logo).

It seems more complicated than I thought... not just a matter of wiring some jumpers and resistors like the 50 - 60 Hz mod.

If someone has a solution or an idea, I will be glad. I still need to get a set of KSS-210b to fix my Sega CD so maybe I could buy the components together. Who knows...
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Post by evildragon » Fri Oct 12, 2007 2:52 pm

TulioAdriano wrote:I've researched on PAL-M to NTSC converters and those have prices around $300. Considering that Ebay has offers of Genesis at $10 (buy-it-now) it might be a better option to buy a genesis and switch the circuit board (of course I don't want that giant Genesis logo).

It seems more complicated than I thought... not just a matter of wiring some jumpers and resistors like the 50 - 60 Hz mod.

If someone has a solution or an idea, I will be glad. I still need to get a set of KSS-210b to fix my Sega CD so maybe I could buy the components together. Who knows...
http://www.jrok.com/hardware/RGB.html

RGB to NTSC.

Oh, btw, if you use an American 32X on your MegaDrive, it will output NTSC no matter what scanrate.

TulioAdriano
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Post by TulioAdriano » Fri Oct 12, 2007 2:55 pm

That's another problem. My 32X is also Brazilian.

I once rented an imported 32X which was NTSC and it really didn't work colorful on my old 90's TV.

I guess I will have to mod both then... :'(
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Post by evildragon » Fri Oct 12, 2007 3:26 pm

NTSC 32X's are known to have cleaner than NTSC genny video output, which is true.

For me, it works great.

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Post by Chilly Willy » Fri Oct 12, 2007 4:56 pm

TulioAdriano wrote:That's another problem. My 32X is also Brazilian.

I once rented an imported 32X which was NTSC and it really didn't work colorful on my old 90's TV.

I guess I will have to mod both then... :'(
If you get the RGB to component converter, you'd only need to put it in the 32X. Remember, the RGB from the Genny is input into the 32X which then mixes that with it's own RGB and then outputs that, so you'd only need to convert the final RGB output from the 32X.

TulioAdriano
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Post by TulioAdriano » Fri Oct 12, 2007 6:24 pm

Chilly Willy wrote:(...) so you'd only need to convert the final RGB output from the 32X.
Except when I play the Master System power base converter. In that case I need to have the 32X out of the way... :(
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Post by evildragon » Fri Oct 12, 2007 7:02 pm

I was going to mod my 32X for PAL output, and I remember all I had to do was replaced the crystal, AND remove a jumper. I still know the region modding for the 32X, and I can take apart my 32X if you guys want to know that "trick".

For the crystal, that's for the color sub carrier.

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