RGB gaming questions

Ok, I'm hooked.

I have a Sony PVM with RGB+Sync connectors so I'm set on displays.

I know SCART supplies RGB and after finding this link ( http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm) I feel I could build a SCART cable for any console I want to use on my PVM.

Thing is, I'm in the US, SCART is kind of useless here so building SCART cables for all my systems only means I need to build a SCART-> RGB unit to actually plug anything into my display. Would I be better off making some custom instead?

Heres the main questions I have.

1. According to that site above, all those consoles regardless of region, supply RGB through their normal output jack, you just need a cable that actually runs the correct lines to use them, no internal modding needed?

2. If all those consoles supply RGB through their normal output, why are there guides to solder leads onto the CXA1145 chip in a Genesis/Neo Geo to get RGB? Is it somehow better?

2. for RGB+Sync on the back of my PVM, Sync is actually just composite video, its just used for sync instead of picture data? For instance if I'm making a custom non-SCART cable for a genesis, I connect the pin normally used for composite to the synch input on the PVM?


I'm thinking of building a little box that stays connected to the PVM that gives me easy access to RGB and Sync without having to reach behind the monitor. The idea would be to have some sort of standard plug such as SCART or RCA jacks that I can connect some standard cable to when I build new AV cables for my consoles. The box would also have connections to accept bare wires (like on the back of speakers), so If I'm working on an Arcade board I can connect it to the monitor without having to solder any connectors.

thoughts? corrections?

Finch said:

Ok, I'm hooked.

I have a Sony PVM with RGB+Sync connectors so I'm set on displays.

I know SCART supplies RGB and after finding this link ( http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm) I feel I could build a SCART cable for any console I want to use on my PVM.

Thing is, I'm in the US, SCART is kind of useless here so building SCART cables for all my systems only means I need to build a SCART-> RGB unit to actually plug anything into my display. Would I be better off making some custom instead?

Heres the main questions I have.

1. According to that site above, all those consoles regardless of region, supply RGB through their normal output jack, you just need a cable that actually runs the correct lines to use them, no internal modding needed?

2. If all those consoles supply RGB through their normal output, why are there guides to solder leads onto the CXA1145 chip in a Genesis/Neo Geo to get RGB? Is it somehow better?

2. for RGB+Sync on the back of my PVM, Sync is actually just composite video, its just used for sync instead of picture data? For instance if I'm making a custom non-SCART cable for a genesis, I connect the pin normally used for composite to the synch input on the PVM?


I'm thinking of building a little box that stays connected to the PVM that gives me easy access to RGB and Sync without having to reach behind the monitor. The idea would be to have some sort of standard plug such as SCART or RCA jacks that I can connect some standard cable to when I build new AV cables for my consoles. The box would also have connections to accept bare wires (like on the back of speakers), so If I'm working on an Arcade board I can connect it to the monitor without having to solder any connectors.

thoughts? corrections?

Click to expand...

First, Tim Worthington is the fucking MAN! I have built several of his SCART to arcade monitor circuits and they work fantastic

1. Yes, the consoles that Tim lists output RGB from their stock connectors, no internal modding needed. However, some consoles need 220uf caps or 75ohm resistors put inline with the RGB signals, he indicates this on his site.

2. Well, as it was described to me in the Genesis case, the RGB is output from the CXA1145 chip, then it goes through a voltage divider before it hits the connector on the back of the console. So tapping the RGB right at the chip should lead to brighter colors. What I have found in my testing is that tapping the RGB before the voltage divider does yield brighter colors, however, it made all the colors look like crap. For example in Sonic 2, sonic was more Grey than blue, however adequately bright. The best results I have found is tapping the RGB at the rear connector (after the voltage divider) then adding the 75ohm resistors and the 220 uf caps. This gives a nice blended color, but it is too dark for arcade monitors - using the amplifier schematics Tim provides, the picture ends up looking great and plenty bright on my arcade monitor.

2a. As far as the SYNC signal is concerned, the SYNC signal will be stripped off the composite connector. So you just hook up the normal composite connector and inside the TV there is a LM1881 or similar to strip the SYNC signal off the composite.

Hope that helps

Thanks!

yup, that helps. Good to know the source of those SCART schematics is good. Not sure if I'll bother with actually using SCART but it'll work the same through some custom cable.

I see your cleverly addressed the stupid fact that I had 2 question #2's whoops.

For a multi console application it is best to standardize your setup. If you do make a scart cable I think a box would be better that has the inline 220uf caps and 75 ohm resistors with switches for bypass on the RGB lines so you can switch it on and off.

good idea, It looks like there are only a few combinations of resistors and caps that one would need on the RGB lines anyways, bypass switches would be easy, and fun to play with.

Xian Xi said:

For a multi console application it is best to standardize your setup. If you do make a scart cable I think a box would be better that has the inline 220uf caps and 75 ohm resistors with switches for bypass on the RGB lines so you can switch it on and off.

Click to expand...

For literally the best quality RGB you actually want to get it off the DAC and buffer it with an amp (simple voltage follower and only depending on the pixel register logic family) or remove the encoder entirely and simply AC couple/directly drive the TV.

You also don't want sync from composite video unless absolutely necessary... It's better to find the digital sync source and once again directly drive. TTL rises to a bit over 3V, TV wants .3V into 75 ohm, all you need is a 680 ohm series resistor. You can't rely on a display to be intelligent and in this case there isn't even a need to...

Edit: *sigh* duplicate post

Kyuusaku said:

Edit: *sigh* duplicate post

Click to expand...

Hey whats up! Long time no see.

I don't know if it's the best solution, but what I've done for my RGB setup is use standard SCART cables for everything, run them into a SCART switchbox, then use a homemade SCART->15 pin cable from the switchbox to the monitor. Unofficial SCART cables are cheap, SCART switchboxes are cheap, and you don't have to mess around inside consoles at all. Search ebay.co.uk for sellers that offer various SCARTs and you should be able to get every console SCART cable in combined shipments from 2 or 3 sellers. Just need to make sure you get a SCART switchbox that's fully wired for RGB, some are wired for composite SCART only.


The biggest problem that I had, using an NEC XM29, is that it won't sync on composite video. It was easy to change most of my SCART cables to re-route sync directly from each console's A/V connector sync pin to the monitor sync input. I just swapped sync output onto the cvideo pin. (20) But, the sync signal from some consoles (like NGCD & Nintendo consoles) isn't compatible with the XM29... I had to use LM1881's on those. I don't think you'd hit any of those issues on a Sony PVM though since it can just use cvideo for sync. Should just be able to use standard SCART for everything and build one custom output cable to get to the monitor.

EDIT: A couple other comments...
Even though I have a model 1 Genesis, I went with a custom model 2 -> SCART cable that pulls audio from the headphone jack. I can use the cable directly with my 32x or CDX and if I want to use the bare model 1 Genesis, the 32x model 1 adapter cable can connect directly to the model 2 -> SCART. The headphone jack connector will pull stereo from any configuration, even 32x audio is pushed back through the Genesis 1 for mixing and 32x stereo comes out of the model 1 headphone jack.

My NGCD cable is also custom, with 2 RCA audio inputs. The NGCD doesn't output stereo through the A/V connector, so the RCAs plug into the back of the console and feed audio to the SCART connector.

I probably could have built my own, but I got both of those custom made-to-order cables from:
http://www.retro-accessories.co.uk/ourshop/cat_150582-RGB-SCART-cables.html
(aka pcenginesales on ebay.co.uk)
Quick replies, great quality, and they even wired up my sync to SCART pin 20 configuration.

Got a few other cables from this seller:
http://shop.ebay.com/gamekingno1/m.html?_nkw=scart
Just keep in mind that their cables are built for the European PAL resistor & capacitor configurations. ie their GC cable has the 220uF caps that you'd need for RGB on a US SNES.

Along the same lines, If I wanted to make a CMVS that used a Neobitz for S-video and Composite, but then also have an AES style port delivering RGBS and Audio for use with an AES SCART cable, do I run into weird issues? Is there anything wrong with running RGB and Sync to an external port and into a Neobitz?

I wouldn't be using both at the same time.

Also, I see a lot of Neo Geo CD SCART cables on ebay, are the same as a Neo Geo AES SCART?

NeoGeoCD and AES RGB cables are the same. Thing to note though is the cables' country or origin. Japanese 21pin RGB cables and Euro SCART RGB cables use the same connector and look the same. However they are wired totally differently.

So if you want to use Euro SCART cables, be sure those NeoCD cables are in fact Euro NeoCD cables.