Scart-to-Scart RGB Mod Tutorial

[huwwatkins]

Cheers - After a bit of research it seems that some tv's only work with composite sync. Any idea why that is? I am tempted to try and see what the differences are on a scope.

[zyrobs]

You'd have to ask an engineer for a real answer to that.

[huwwatkins]

I've managed to aquire a scope and the ear of somone who knows that they are doing with one. Will be interesting to see how different the two sync lines are.

[buckoa51]

After a bit of research it seems that some tv's only work with composite sync

You mean with composite /video/ for sync? I've never known a TV to not work with raw sync, but I've not exactly tested hundreds.

[huwwatkins]

Yes- when using the composite video out for sync (TP8) everything is ok ( although I get some odd scrolling lines in the image) but using pure sync (TP4) it doesn't like it and flickers as in the video I posted.

[huwwatkins]

Fixed the problem by putting a 500ohm resistor on the c-sync. I think the tv was not linking the higher dc voltage on the c sync compared to composite

[buckoa51]

Ah, thought you'd already tried that, yes that's needed on some TV's

[huwwatkins]

I'd tried putting a 180 ohm resistor on an then two in series but it didnt work. Magic number was 3 in series for a grand total of 540ohms

The two signals looked totally different on a scope though!

[Paianis Harper]

Apologies for thread resurrection, but wouldn't it have been a bit easier to mod the video for component out? I mean, that reduces the chance for interference even further because like Composite and S Video, the audio and video signals are separated entirely. Its also easier to drill the spaces for the 5 RCA plugs on the back.

Maybe I'll try this out one day...

[buckoa51]

The audio and video are separated entirely with RGB too. Plus component would require transcoding (you going to fit a transcoder internally?) and would actually very very slightly degrade picture quality over RGB.

[zyrobs]

I think he means that they use separate cables. Scart just has them in separate pins, but in the same cable, so unless the cable is properly shielded there is chance for crosstalk (that causes the audio buzzing).

And yeah, the Saturn doesn't output component, so you can't just drill some RCAs to it.

[Paianis Harper]

Well actually, I think it would technically be possible butI don't know of any TVs that would except an RGB signal through its Component input, which I think is a real shame because Scart connectors are rubbish. Not to worry though; there is always VGA (D-Sub) and I'm pretty sure RGB is a standard for this, just as it was on the Dreamcast.

[zyrobs]

VGA is indeed a standard, but it's a standard for 31khz signal, while scart rgb is 15khz. So it will be almost entirely useless unless you own a multisync monitor that can take 15khz signal, like certain Amiga ones.
Or, use it with one of those cga to vga converters, but those are of questionable quality.

There are also certain projectors that take 15khz RGB input through vga connectors.

[buckoa51]

I don't know of any TVs that would except an RGB signal through its Component input

Some projectors and video processors can, but where on a normal component input would you connect the sync cable anyway?

[zyrobs]

It could take sync from the composite signal. My projector does that; the RGB pins on the d-sub input can take either 31khz RGB+H/Vsync, 15khz RGB+Csync, or YPbPr component. I had to make a hefty dongle for that thing...