Mega Drive composite sync output?

Started by albino_vulpix, July 12, 2008, 04:28:37 PM

Previous topic - Next topic

albino_vulpix

In an attempt to get a cantered image with my Mega Drive through a scart connection, I'm going to try swapping the composite video on scart pin 20 with the composite sync signal. But before I take it apart, anyone know the MD's csync Vpp? Or more importantly, if a scart TV can use it?

NFG

The MD's sync is compatible with pretty much everything, you should be OK.


NFG

Quote from: viletim on July 13, 2008, 01:37:05 AM
Lawrence, that's crap.

http://nfggames.com/forum2/index.php?topic=2097.0
Never mind the tone of your post, you're quite correct!

What I meant was that it's not using any weird frequencies or voltages, certainly nothing that would harm his TV.

Should definitely add your info to the wiki...  I'll do it later today if you don't beat me to it.

albino_vulpix

So I'm going to need a sync splitter similar to what segasonicfan used?

viletim

Quote from: Lawrence on July 13, 2008, 05:56:15 AM
Quote from: viletim on July 13, 2008, 01:37:05 AM
Lawrence, that's crap.

http://nfggames.com/forum2/index.php?topic=2097.0
Never mind the tone of your post, you're quite correct!

haha - well...megadrive sync does seem to be the one that people have the most trouble with.

albino_vulpix,
I think this is what you really want:
http://members.optusnet.com.au/eviltim/shiftysync/

If you really just want to drive the composite video input with your sync signal then you can buffer it with any non inverting logic gate. A good choice is the 74HC32 - powered by the 5 volt rail. Connect all inputs and outputs together for maximum current and put a resistor of about 470 ohms in series with the output to bring the signal down to video voltage levels.

Tiido Priim├Ągi

On my MD2 (and MD1) I built my own sync signal out of H and V sync the system's VDP provides to get centered image. 2 transistors and 2 resistors. Check last post : http://www.sega-16.com/forum/showthread.php?t=3718&highlight=csync&page=4

Adjust the 120K resistor for image position. Note : it works perfectly for games that use 320 pixel wide res, for games that use 256, the image is not centered anymore (still better than without this), and may be slightly out of shape on upper part (but that maybe just my TV...). Anyway, it works, and its simple enough to try. You can grab the H and V sync from MD cartslot (check the pinout, its on this site).
Mida sa loed ? Nagunii aru ei saa ;)

RGB32E

#7
Quote from: Lawrence on July 13, 2008, 05:56:15 AM
Quote from: viletim on July 13, 2008, 01:37:05 AM
Lawrence, that's crap.

http://nfggames.com/forum2/index.php?topic=2097.0
Never mind the tone of your post, you're quite correct!

What I meant was that it's not using any weird frequencies or voltages, certainly nothing that would harm his TV.

Should definitely add your info to the wiki...  I'll do it later today if you don't beat me to it.

Filtering CSYNC with a 220uf or 100uf cap (just like R, G, or B wo/series resistor) fixed the CSYNC issue for me... so it isn't necessary to do anything elaborate to get a working sync...  (tested NTSC Genesis 2 and CDX connected to a Sony PVM-2030 - for reference)

// Forgot to mention the JVC X'Eye (NTSC/U) as well...

albino_vulpix

#8
I just tried it through a 100uF cap.

Bright.
Stable.
TVs perfectly happy with it.
SHIFTED arg.


I do appreciate the suggestion however :)
I'll try viletim's suggestion when I can get to Dick Smith, hopefully my local one has some.


albino_vulpix


viletim

albino_vulpix,

For a sync driver? Yeah, you could use that...

It's an inverting gate so you have to use one gate to invert the signal then connect the output to the inputs of the remaining gates. That way you invert the signal twice and get the correct polarity on the output.

albino_vulpix

Thanks. So finally, is this how I'd connect everything?



The capacitor is there because the TV needed it to use the unbuffered signal. Would I need it now?

albino_vulpix

So I tried the sync buffer with a 74HC02.
I tried 2 gates in series, with another 2 in parallel:
(sync in-1A-1B-2A-2B), (1Y-2Y-3A-3B-4A-4B), (3Y-4Y-470 resistor-220uF capacitor-TV)
Rolling picture.

I tried just 2 in series:
(sync in-1A-1B), (1Y-3A-3B), (3Y-470 resistor-220uF capacitor-TV)
Just as the composite video gives. Stable, bright, shifted.

Then I tried 4 in series, same as above. So over all, failure :( I was using Turbo Outrun as a test game, if that makes a difference.

I like TmEE's method, except for the select few that don't work with it. I think I'll build the shifter posted, looks fun.

excelsior

#13
I have this issue when connecting the japanese Mega Drive [HAA-2510], non TMSS, in RGB using the GBS-8200 converter:

Problema sincronia Mega Drive [Sega Genesis/Mega Drive issue] HAA-2510

The Snes RGB works perfectly using this converter.
Anyone have any idea? This problem occurs with both csync and composite video pin (i used composite video as sync too)