Dreamcast/JAMMA/RGB question

Prythee,

I'm currently trying to make a SuperGun for my ST-V board. As I didn't have a SCART connector lying around, I decided to sacrifice one of my Dreamcast RGB leads (can still get loads for 1e apiece so no big loss). After quite some time spent measuring and subsequently soldering, I decided to hook the whole thing up to my TV... and now I've got a perfectly black image :angry

Using my voltage/impedance/whatever meter I checked all the relevant connectors - R,G,B,Sync and GND. They all seemed to be connected just fine, but I did notice a rather irregular reading on the R, G and B pins - turns out there are capacitors in the SCART connector! Now that made me wonder, are they only required for the Dreamcast - because it has a higher voltage level, perhaps - or should they be there in all cases? I've tried looking for data on the JAMMA and Dreamcast voltage levels, apparently JAMMA is up to +2VDC but I couldnt find any info on the Dreamcast's voltage level.
Should I take out the capacitors?

 

btw, the caps are 220uF.

 

I've had PS1/2 RGB SCART cables with the same cap's - I don't know what difference it makes, if any. The one with the cap's seemed to look better, but maybe it was just because it used better cable.

Did you remember about the RGB blanking singal thingy? Pin 16, I think?

 

thanks, the blanking signal could very well be it - I got impatient so I removed the caps, but still no result. Then I tried it on my other TV (which doesnt even support 60hz) and I got a very garbled B/W view of the ST-V's service menu, barely readable. I'll mess a bit with the blanking signal.

 

Yeah, you need to put 1-3V DC on pin 16, otherwise the TV won't know it's an RGB signal so it'll be black or barely visible. I think I put 5 or 12V on it when getting the RGB out on my Spectrum to work, but I doubt that's good for my TV...

 

Yeah, he's right :smt023
You forgot the RGB pin, but I think you have to put more then 3V. Do like I did, just wire it directly from the +5V on the power supply.
And while you're at it, you could also wire the +5V to Pin8(?) so it automatically changes the channel on your TV to AV/Scart when you power on your board.

@Zilog Jones, I think most tv's are ready to handle up to 15V/16V, so 12V should be alright.

About those capacitors, all my systems have those capacitors in their respective cables, but when I made my supergun I didnt bother to put them in.
It works flawless on my tv, the colors are a bit 'stronger' then on the consoles, it looks just like an arcade monitor.
However you might experience different results on different tv's, like bleeding colors and some distortion from flashes and bright images.

 

Oh, great, thanks - so the 12V isn't slowly killing my TV! I think my Spectrum might need those cap's though - the colour bleeding is hideous! One bright colour would tint most of the screen that colour too!

Maybe my TV's just shite. It may be a Panasonic, but it's made in the Czech Republic...:smt009

 

From my personal experience the big brand tv's and modern tv's are the most picky with stuff like this

My tv (a cheapo Crown btw) works fine with every system and survived all sorts of abuse with all sorts of consoles, jamma boards, damaged jamma boards, 31khz rgb video through the scart (dont ask) and some heavy experimenting on a saturns video chip, clock and encoder chip (again, dont ask).

However I frequently see friends of mine with Sony and other big brand tvs with weird problems, like weird colors, some rgb cables dont work at all with them, off centered picture with some systems, etc

 

Its late so I can't think straight, but let's see....

pins 7, 11 and 15 for R,G,B. Hook the R,G,B grounds up (5, 9, 13) if you like.

sync to pin 20

video ground to pin 17

+5V to pin 16 THROUGH A 100OHM RESISTOR!

Why the resistor? Cuz actually, SCART standard says this pin accepts 1-3V. So let's not feed it 5V and DEFINATELY not 12V.

Don't forget that some systems use HSYNC and VSYNC and others have a combined sync or just use one. You should be fine going like this, though.

And yes, take the caps out.

 

OK thanks! I actually did put the 100ohm resistor on the 5V line coming from the PSU but I havent set soldered it to the SCART, as I thought it would be in the connector anyways seeing it was a DC SCART cable... but then I remembered... I didnt wire the +5V line of the SCART cable so the pin is getting no power *doh* :smt1062

 

Boy, am I really glad I live in an NTSC region, and my near-blindness allows S-Video to look beautiful enough...

I don't think I might be able to do all that custom SCART and RGB wiring without truly damaging one of my babies...

 

The problem would be that a JAMMA board outputs only RGB... it is pretty much SCART-ready, but to get it to output S-video or something else requires additional circuitry... damn, why does the Naomi have VGA and the ST-V only has line out :angry

 

W00T I wired up pin 16 and now it displays fine! Though the colours are a bit oversaturated at times, seems like my careful desoldering of the caps was in vain :smt009

 

Xerdo, arcade hardware isn't NTSC, it outputs RGB. You'd HAVE to do lots of soldering - and what's more, you'd need to build a circuit to convert that RGB signal to s-video!

People in SCART countries have it easy when making superguns ;-)

 

Whoa.

I hope there's schematics for you guys....

I don't know but I'm not really into very complex hardware modification, not because I don't like them but because I really don't trust my abilities with the soldering iron.

 

You're not really modifying anything when doing all this for SCART connections - you're just wiring up some cables...

 

Then I'm being overly paranoid??

... wait. This means I can actually get the guts from any arcade, from the 80s or 90s and hook them up to my TV??? Does something like System 16 or the "universal" class conversion have a "standard" console one can get and hook up?

This is what they call a "supergun"?
Then the STV is that saturn thing with cartridges.... wow.

Can superguns' guts be exchanged...?
Are new arcade systems supergun compatible?

Whoa.

 

A supergun is JAMMA standard. It will take standard JAMMA boards ONLY. It is a means of connecting that board to your TV instead of an arcade machine.

To play ANY other board, e.g. ST-V, MVS, playchoice, CPS, JAMMA+...... or anything older than the JAMMA standard or not conforming to it (yes space invaders, galaxian, defender etc.), you need an adapter.

 

That's an adapter to play that board into the supergun, or an adapter like the one Anti built, that goes directly from the ST-V board to the TV?

 

That depends - sometimes you can get adapters that convert a board's proprietary outputs into JAMMA, or sometimes it goes directly to the TV. My Supergun is very simple (I will put pictures up soon) - just a JAMMA connector that I bought in Tokyo with several wires soldered to it, hardly any components - there's a female molex connector (like on hard drives) for the power - so I can hook up any PC PSU - 2 wires running to a salvaged PC internal speaker, and about 6 wires from a cannibalized Dreamcast SCART lead. And yes the ST-V is sort of a Saturn with cartridges, but I have heard rumours of additional RAM and even anti-aliasing (?)