Questions about Scart and RGB on BNC's

[CABAL]

Hi all.

My wife loves playing Burnout 2 on the Gamecube, but I have a hard time
relaxing when the image is sent through composit to our 33" Barco
Monitor. Our Dreamcast looks stunning with the VGA cable, so I want
the same for the Nintendo.

I have the RGB Scart cable for the cube, but I hate scart, so I soldered
some BNC's on the leads instead(first removing the leads from the
scart plug). Funny thing is, there's no ground for RGB only for the sync,
that's odd. Furthermore, inside the scart plug, there are some (insert
english word here, please) thingys that say: uF10v 220uF10v on the
Red, green and blue wire. What do they do? (I know they're probably
capacitors, but why do they need to be there)

Anyways, I soldered some BNC's on, leaving the thingys in the chain, and
the pic looked OK, but very dark, and with horizontal lines after some of
the graphics. So, I guess, not very OK.

Should I remove the thingys, or forget about making the cable(very short)
without ground on RGB, or should I use a DB9(TTL) plug instead?

Thanks for your time,

Nicholas

[NFG]

The shape of your plug (or plugs) is irrelevant, the quality of your soldering is more important for image quality.

WHY the capacitors are there isn't as important as the fact they MUST be there.  If you remove them things go funny.

All electric circuits need ground, if you don't use it things don't work.  Note that using a PAL system and an RGB cable will not give you VGA; no PAL games are compatible with progressive/31kHz RGB output.

[CABAL]

Thanks, but how come there's no return for R, G and B on the scart? The
composit do have a return. Is this bad cabling from their part?

Nicholas

[Darklegion]

Its bad cabling but you probably won't notice a difference in any case.All the grounds will be connected internally 90% of the time,some high-end tvs/monitors might have the individual grounds isolated but this is quite rare.

[NFG]

You only need one Ground, typically it's shielding around the cable.  Component (And I assume you meant component, not composite) has a return for each signal because of the connector it uses and the fact it has 3 individual cables, each requiring shielding.  SCART has only one cable, so only one shield is used.

More grounds are better, but only one is required, and since it seems to work just fine, why use more?  Also RGB uses higher voltages for the signals so it's less prone to interference.

As long as one ground connects both the transmitter and receiver, the whole system will be happy.

[Guest]

First of all, thanks for you postings!

So, my composit video/Sync(pin 20 on the scart) has been connected to the
BNC I want to carry composit sync. This has a return(pin 17 from the scart)
connected to the BNC too, so that is OK, the image syncs fine.

Then I have RGB, all with the capacitors, connected to three BNC's, without
return(since it's not there in the cable->scart). The ground pins are just empty.

The pic comes on, but is dark, with long shadows.

Can I take the gorund from, hmm, the audio ground and connect to the ground
on RGB? or maybe sync ground?

Thanks again!

Nicholas

[NFG]

All grounds are the same, and all grounds should be connected.  It doesn't matter WHERE, just as long as they ARE.

[Dr.Wily]

Buy a YUV compoment cable with RCA to BNC convertor. It's work fine !

If you have RGB out on your GC you live in europe ? Wath your country ?

[CABAL]

All grounds are the same, and all grounds should be connected.  It doesn't matter WHERE, just as long as they ARE.

Thanks, I'll split out the ground then.

By the way, one of the ground has a resistor on it, what does that do?
It was connected to pin 18, do I need to do something with that?

Keep in mind that I want to be able to use RGBS on BNC's:)

Thanks again for your time!!

Nicholas  

[CABAL]

Buy a YUV compoment cable with RCA to BNC convertor. It's work fine !

If you have RGB out on your GC you live in europe ? Wath your country ?

I live in Denmark!

Nice forum.

Nicholas

[Zaarin]

Pin 16(not pin 18) is for switching TVs to RGB mode when you turn on the console. Not all TVs require this though. If your TV works without it, you don't have to connect that wire. Pin 18 is the ground for pin 16.

[Aidan]

The pic comes on, but is dark, with long shadows.

Can I take the gorund from, hmm, the audio ground and connect to the ground
on RGB? or maybe sync ground?

Dark with long shadows suggests that there's a grounding problem. I'm a little surprised they didn't ground the RGB returns, as some TVs do not operate well without them. That includes the Philips I have which gets a bit upset if there's no return for RGB. This is where I disagree with Lawrence a bit here, as there should be a ground for each of the RGB signals. The frequencies that are involved don't tend to like taking a roundabout route, and that route often encounters what is effectively a low pass filter.

Taking it from the sync ground is a fair idea, more so than taking it from the audio ground.

[NFG]

Whoah, I never ever said leave it un-grounded, I said everything that is a ground should be grounded!  If you've got 10 grounds on a cable connect them all or suffer the consequences!

[Aidan]

I think we're a little at crossed purposes here! It was just the comment about "You only need one ground, typically it's the shielding around the cable." that I had a little bit of an issue with. It'll work with just the shielding of the cable, but if there's seperate returns for RGB, the image quality tends to be that bit better, even if those returns are connected together at the far end (transmitter end) of the cable. That way you tend to avoid any cross coupling caused in the cable; the longer the cable the worse these effects can be. This is especially so on the cheap and nasty cables that often get used for SCART.  

[CABAL]

Thanks! I'm now in the process of resoldering the leads to my connectors, but
(ARRGH) now I can't remember what goes where!! Sometimes I really hate
myself.

Does anyone know what color the sync lead should be(and sync gound)?

The same goes for audio and audio ground...

Thanks, hope you can help, I simply can't stand watching the GC image after
playing VGA DC:)

Nicholas

[NFG]

The colours of your wires could be anything, there's no standard.  Get out the multimeter and check the other end.  

[Dr.Wily]

I live in Denmark!

If you live in europe you have a PAL GC. And PAL GC have a RGB out. Buy GC RGB cable or use SNES RGB cable.

It's work fine.