Options for RGB to s-video and/or composite

[martianviking]

I'd like to explore the options for converting the RGB output of a JAMMA board for display on a North American television set.

I am not considering the option of finding an RGB monitor to accept the RGB video from the JAMMA board; I specifically want to output to a standard North American television set.  I am going to use NTSC s-video and composite video as the preferred output methods, but I would also like to consider the option of converting to SCART first and then converting to a standard NTSC s-video or composite video (or perhaps even Y, Pb, Pr component video).  I've listed the methods that I can conceive of; perhaps some of you can offer some input on the merits of (or problems with) each.


Option 1: Buy a converter from Jrok.

This would seem to be the easiest method.  Do a search or two for RGB and JAMMA, and you'll undoubtedly be led to his site over and over again (directly or indirectly).  He will sell you a small circuit board that accepts the red, green, blue, sync, and ground wires from a JAMMA video output (plus ground and +5v for power) and outputs s-video and composite video.  At the time of this posting, Jrok's board has gone through a number of refinements and is at "v3.1" (it comes highly recommended from a number of sources and seems to be the only professionally constructed product of its kind).

The only drawback I can see to this option is the cost; the last quoted price I saw was $95 (United States dollars).  This is a bit too much for some people (including me), but the option has to be mentioned, at the very least.

Jrok's "RGB to TV converter" can be found here:
http://www.jrok.com/hardware/RGB.html


Option 2: Build a converter yourself.

This will be difficult (Jrok doesn't sell his schematics), but it apparently has been done.  A person with decent soldering skills and some relatively basic electrical enginering knowledge would probably be able to do it.

I found a brief description (but no detailed instructions) here:
http://www.mikesarcade.com/cgi-bin/spies.c...FAQ.rgb-vga.txt

Several chips exists to do this conversion, and require only a crystal, and some termination resistors. However, it should be noted that unless you are willing to pay for the more expensive chips, the picture isn't that great, sort of like a cheap video camera image.

Analog Devices' AD720 chip is the most expensive, but will give very good results.  It is a little under 20 UK pounds. Sony do three cheaper chips, each one with a different price, and different picture quality.  I tried the 1645 which is about 6 UK pounds.

Instructions can, I believe, be found on the packaging, but suffice to say that you connect up the crystal or clock source to the pins indicated, terminate the RGB into 75 Ohms to ground, and feed them into the RG and B inputs on the chip, along with the composite sync in.

The composite video out can then be taken and fed into your TV or video. For those with S-Video equipment, the chips also output seperate luma and chroma so you can get an improvement in picture quality by not having to combine them.

Option 3: Output to SCART then convert to NTSC.

This option looks like the best combination of low cost and relative ease, assuming that you can find a cheap SCART to NTSC converter.  Apparently it is very easy to channel the output from a JAMMA board to a standard SCART plug.  I found directions on doing so in a couple of places.

Here is one brief description of the JAMMA pinout relationship to SCART:
http://www.solvalou.com/messages_view.php?mid=127

The source of this quote can again be found here (please forgive the screwy ASCII art in my quote):
http://www.mikesarcade.com/cgi-bin/spies.c...FAQ.rgb-vga.txt

Simply connect the RGB out from your game to the RGB in on the socket (buy a plug, it's a *lot* easier than poking wires in the socket). Next, connect the video ground to the RGB grounds, and connect the composite sync output to Composite Video In on the SCART socket.  This last stage is because the TV doesn't care which channel it gets its sync from, RGB or composite video, it all goes to the same circuit.

On some TVs you must tie the blanking pin low, but for most this will work straight away.  And that's it.  Just select the correct channel on your TV for SCART input.  You can also feed the sound in through the SCART port, but be careful not to turn the volume up on your game board, you could damage the TV.  Keep it low, and it should be fine.

Here is the pinout for a SCART plug, courtesy of John Keay.  Again, you use this information at your own risk.
     
[size=8]                   +---------+
Audio Output B     |  1      |
                   |      2  | Audio Input B
Audio Output A     |  3      |
                   |      4  | Audio GND
Blue GND           |  5      |
                   |      6  | Audio Input A
Blue               |  7      |
                   |      8  | Function switching
Green GND          |  9      |
                   |      10 | Comm data line 2
Green              |  11     |
                   |      12 | Comm data line 2
Red GND            |  13     |
                   |      14 | Comm data GND
Red                |  15     |
                   |      16 | Blanking
COMP video GND     |  17     |
                   |      18 | Blanking GND
COMP video output  |  19     |
                   |      20 | COMP video input
Common GND         +--21-+   |
                          \  |
                           \ |
                            \|
     
     
Game                 TV
Board          Pin name   pin number(s)       
-----        -----------------------
Red            Red          15
Green          Green        11
Blue           Blue          7
GND            Grounds       5, 9, 13, 18, 21
SYNC           Video input  20
+5             Blanking     16[/size]
     
The RGB inputs are active high (i.e. "standard" RGB levels) and the SYNC signal needs to be an active low combined vertical and horizontal sync (i.e. a JAMMA-like SYNC). The only problems I had were when I didn't connect the blanking pin (the picture synced up but everything was nearly black). Pins 8 and 16 on a SCART port as supposed to be used to select different kinds of source signals (UHF, RGB or Composite video), my TV didn't seem to care so I left them unconnected, but here is the coding table just incase.
     
[size=8]Pin 8  Pin 16
   0      0   UHF
   0      1   RGB
   1      0   Composite video
   1      1   RGB[/size]

After you have a working SCART plug from your JAMMA board, you can use any standard SCART to NTSC converter.  These can be very expensive (more than Jrok's converter), but I have also found them for as cheap as $3.49 (United States dollars).  Undoubtedly these cheap converters will not give you optimum video quality, but if you use s-video, it should be at least acceptable.  Also, this at least gets you up and running and leaves you the option of buying a higher-quality SCART converter later (since you would simply need to unplug the one you have and plug in the better one).

SCART to NTSC (composite and s-video) converters can currently be had for cheap from the following places (I do not endorse any of these vendors, they are provided for reference only):

http://www.lik-sang.com/?click=pi-121-1467-link
http://www.play-asia.com/paOS-13-70-14r-4-1-71-t.html
http://www.the-console-corner.com/xbox_scart.htm
http://www.js-technology.com/rgb-svideo/
http://www.audiovisualonline.co.uk/dynamic...oo/display.html
http://www.gadgetsuk.com/xcart/catalog/Sca...or-p-16140.html


So, can anyone offer any insight?  Have I made any drastically incorrect assumptions here?

[NFG]

Excellent question, bonus points for covering all the bases.  Half a point lost for length, I tuned out and napped a few times while reading it all.

I'd like to make something very clear to everyone who wants to play arcade games at home:  It's a sign of madness, and it will result in one of three things:  

1. You'll go broke
2. You'll learn mad technical skills
3. You'll get sick of the inconvenience and flog it all.

These things aren't necessarily mutually exclusive, you can go kinda broke while learning a few skills, but there's a trade-off here: if you're not willing to make and break your own hardware then you're gonna have to pony up the dough to buy someone else's solution.

The scart-before-encoder thing is kind of irrelevant, since most/all encoders have RGB passthrough and you can put your scart output after the encoder.

A $3.50 SCART->Composite device is an ADAPTOR, not an ENCODER.  The SCART plug can be used for composite, S-video or RGB, for that price all you're getting is a physical connection changer, not a video encoder.

You've not mentioned the XRGB upscan route, presumably this VGA-monitor solution doesn't coincide with your desire to use a normal TV.  What about the (also from Micomsoft) XAV-2s adaptor?  It's the same price as a jrok but comes with an actual encloser.  It's a consumer-level all-purpose device with two RGB inputs, S-vid and composite output, stereo audio output, and a power LED!

Only available in Japan of course, but you can get one through me if you want one.

[martianviking]

Excellent question, bonus points for covering all the bases.  Half a point lost for length, I tuned out and napped a few times while reading it all...

I completely agree.  Even my eyes were glazing over while I was writing it, but I really wanted to get all that information out there so that it could be examined, refuted, and maybe used by someone else.  I don't know if I'm going to do any better with this one.  

...I'd like to make something very clear to everyone who wants to play arcade games at home:  It's a sign of madness, and it will result in one of three things: 

1. You'll go broke
2. You'll learn mad technical skills
3. You'll get sick of the inconvenience and flog it all.

These things aren't necessarily mutually exclusive...

Again, quite right.  Three things everyone should consider.

...A $3.50 SCART->Composite device is an ADAPTOR, not an ENCODER.  The SCART plug can be used for composite, S-video or RGB, for that price all you're getting is a physical connection changer, not a video encoder...

I suppose that's my "drastically incorrect assumption" right there.  I thought this thing would let me get some sort of picture on my TV, even if the quality would be pretty bad (like those cheap Radio Shack svideo-to-composite converters).  The capacitors in my cabinet's monitor are going out, so rather than buy a new one, I figured I'd just put my MVS next to my VCR like a "normal" person.  Huh.  I guess "Option 3" just won't get it done.  Oh well.

...What about the (also from Micomsoft) XAV-2s adaptor?  It's the same price as a jrok but comes with an actual encloser.  It's a consumer-level all-purpose device with two RGB inputs, S-vid and composite output, stereo audio output, and a power LED!...

Interesting.  I hadn't found that one yet.  I'm assuming you're talking about this:
(Babelfish translation of www.micomsoft.co.jp/xav-2s.htm)

And yeah, if I've got to either do "Option 2" (build a converter myself) or spend US$100, the XAV-2s looks like a solid competitor to Jrok's board.  Only reason I can see going for Jrok is if you want to fit it inside a small case.

Only available in Japan of course, but you can get one through me if you want one.

I guess I've got some decisions to make (like I didn't know that already).

[martianviking]

Just to reiterate:

"Option 3" will not work at all with a North American television unless you get a "real" SCART to s-video converter, which will cost a minimum of US$90, correct?

[NFG]

I don't know anything about the pricing, you may find a bargain, but yes - North American TVs generally don't have RGB inputs so you'll need some sort of encoder.

[martianviking]

Yeah, I had no idea.  I guess the key was that I didn't understand that there are different forms of SCART.  I thought that SCART was SCART was SCART.

Now I see that the SCART format includes many different configurations, some of which do include luminance and chrominance signals.  It looks like if I had that sort of SCART connection, I'd be fine with a $3.50 adapter.

Unfortunately, what we're talking about here is one RGB-only SCART connection, minus the luminance and chrominance signals that s-video needs.  It looks like that cheap adapter would essentially be connecting the s-video output to pins on the SCART connector that have nothing hooked up them on the other end.

So, "Option 3" is essentially like "Option 1" in that I still need to buy an expensive RGB to s-video encoder.  The only difference is that Jrok's adapter is a bare board that accepts wires and a simple plug, while "Option 3" would allow me to use more mainstream RGB to s-video adapters that are packaged in a nice plastic box and expect an input from a standard SCART plug with a live RGB signal.  And then there's always the PAL vs. NTSC issue of most of those ready-made encoders.

It looks like a person either needs to spend about US$100 on a converter or figure out "Option 2" and just build one.  Too bad the guy in that link is building a PAL converter; maybe I'll check out that last part of his notes page and see about making an NTSC version.

[davidleeroth]

Option 2 seems the most interesting

I've used CXA1645M from an early PlayStation to build a RGB SCART to S-Video circuit and it worked well. I believe Jrok uses 1645 too. You might find the schematics for the chip on the Gamesx main site?

[martianviking]

The RGB to s-video encoder that I linked to above does include schematics, notes, stripboard layout, and photos.  The last sentence in the notes section lists the three modifications to the design that the author believes would be necessary for use in an NTSC environment instead of a PAL environment.

For this specific project, since the sync signal is from a JAMMA board and does not include composite video mixed in, you could leave out most or all of the LM1881N "sync separator" section of the schematic, correct?


EDIT:  I found another RGB to s-video converter for sale (in Japan, of course):
http://www.gametech.co.jp/products/catalog/2103/2103_1.html

"This product is horizontal synchronization frequency 15 k Hz analog RGB signal exclusive use."

[NFG]

That gametech device is a phenomenal bargain, but it's not very compatible.  Its claim to work on arcade PCBs is a flat-out lie, it worked on about one of six I tried, refusing to operate with either an MVS or CPS-2 board, and a few others.  I don't remember which one it DID work on, but it's a VERY intolerant bit of kit.  I have a few here, for a hacker it's nice but for someone who expects things to work it's just not worth it, 'cause you'll be re-wiring it anyway.

[martianviking]

Gotcha.  It does look pretty cheap & plasticky, but interesting anyway.  By the way, thanks for everyone's input and straightforward attitudes.  Much appreciated.

Back to the project of building this thing; it would seem to me that the next steps are to figure out whether or not the "sync separator" sub-circuit can be omitted (in whole or in part) and what the parts cost would be.

After all, while of course I do want to learn something in the process here, the original inspiration was to save a little money (and help others to do the same).  Any input on the cheapest source of these parts?

Qty   Type
(2)      33pF Capacitor
(      100nF Capacitor
(3)      10nF Capacitor
(1)      10pF Capacitor
(2)      47uF Electrolytic Capacitor
(1)      100nF Electrolytic Capacitor
(1)      10uF Electrolytic Capacitor
(6)      220uF Electrolytic Capacitor
(1)      4.7M Resistor
(4)      1K Pot Resistor
(1)      47K Resistor
(1)      20K 1% Resistor
(6)      75 Ohm Resistor
(1)      680K Resistor
(1)      CXA1645P Video Encoder IC Chip
(1)      LM1881N Video Sync Separator IC Chip
(1)      74HCT04 Hex Inverter IC Chip
(1)      3.579545 MHz Parallel-Cut Crystal
(1)      21x44 (21 strips) Stripboard

[fragment]

well for RGB to S-video converting, board member D-lite would be a good resource. He sometimes has custom made boards for sale that he claims work better than the Jrok device, and a lower cost. He was also going to share some more info on making your own converter. Here is a comparison of his converter (left) next to a JROK (middle). I will see if he can check this post out.....

[martianviking]

Very nice.  And it looks like his design is much simpler than the one I was linking to.


EDIT:  I'm not sure I deserved any bonus points for "covering all the bases" just yet.  If I would have just used some different search terms, I would have discovered:


Option 4: Use the pre-made circuit from a dead gaming console's motherboard.

A lot of gaming consoles already contain a circuit that takes an internally present RGB signal and converts it to composite video, s-video, or component video for output.  It would appear that this has been discussed on these forums before.

The fourth option is to simply remove the motherboard from a Sega Saturn or other suitable console machine (a dead PlayStation 2 maybe for component out?), then solder the R, G, B, sync, and power leads from a JAMMA board to the correct pins on that console motherboard.  After that, a person could just use the output from that motherboard to provide a signal to their television (they might even be able to use a standard video cable for that console).  I realize that this could leave you with a huge extra circuit board (unless you cut it up), but that's fine.  The easiest and cheapest way to convert RGB to s-video is still the goal here; aesthetics and space-saving are far less important at this point.

It doesn't need to take a lot of space. The part of the Saturn or Genny board that houses the encoder circuit is very small - maybe 1.5" square. You don't need to keep the A/V out port unless you want to for aesthetic reasons. Aside from the oscillator, everything's there and you barely need to rewire anything. I've used this method a number of times in my supergun projects.

If you don't feel like making your own oscillator circuit (which is very easy), you can buy ready-made ones for $2-3. 3.58 mhz is a very common frequency and should be widely available...

...It's not surprising that you're having mixed results with your homemade circuits. The RGB converter circuit is rather finnicky, and if you're not experienced you will run into problems that you know nothing about. Not knowing anything about the basics of RGB or S-Video before going into this project really has the odds stacked against you.

This is why I suggested using the RGB converter circuit from a Saturn - most of the components will already be mounted for you (in a properly designed circuit to boot). Not only will it be a lot less work, but you won't have to worry so much about your own mistakes.

I realize that there are a few mods listed on the main site for getting RGB out of a few popular consoles, but are there any guides anywhere for putting it in for the purposes of converting to s-video?  Of course I'll keep searching, but if anyone can point in the right direction, I'd be nice.

[fragment]

nope, his design is supposed to have that hole circuit implimented. It is all there.

[fragment]

Here is an email from him in regards to building the circuit:

From: owner-turbo-list@joyce.eng.yale.edu on behalf of
d-lite@neo-geo.com
Sent: Saturday, April 03, 2004 9:29 AM
To: turbo-list@joyce.eng.yale.edu
Subject: RE: Turbo/PCE S-Video mod

I use the CXA1645P chip, which is the same as on that UK webpage.  The
CXA2075 is possible too, but haven't tried the AD725 yet (in the very
near future though).  Should be generally the same. Yes, the website you reference is for the PAL format encoder.  The
crystal for NTSC is 3.579....., but I just use a oscillator since is
saves time and space from building your own clock.
To make the circuit, you'd need basically everything on that webpage,
but I would go straight to the Sony Tech Doc for the CXA1645 (easily
found with a Google search for "CXA1645") and use that.  And please
note, EVERYTHING in the tech doc should be implemented.  Every ground,
resistor, cap, ALL of it.
You'll need lots of parts:
680K metal resistors
75 ohm resistors
0.1 uF caps
47 uF caps
10 uF caps
LM1881N chip - sync separator
3.579 MHz oscillator
and various other parts.

Here's a pic of my encoder next to the JROK 3.0 (commercial), next to
an 8PDT switch (3 inches long, for reference): http://home.earthlink.net/~ddragoli/sitebu...SVidCircuit.jpg

The key, obviously, is getting the CXA1645 chip.  My source is
definitely going to be different from yours since I got the larger "P"
chips from NOS sale.  All gone BUT, 2 other easy sources:
Sega Saturn
PlayStation, early models (1001, 5001, 5501)

Those are the "M" chip, SMT's so they're a bit smallish to work with. 
I plan on doing a FAQ on those chips too since it'll be what nearly
everyone uses.
To answer your other question, Yes, I'll be offering premade boards if
people want them in the future.  At the moment, I don't have many to go
around (most sold into mods for people).
Remember, this mod takes PATIENCE!  Even if you're good and everything
works the first time, building the whole circuit from scratch will take
you minimum 3 hours.  Getting the chip from the Saturn is a different
story since you'll probably be able to keep some of the resistors and
caps intact.
More info in the future!
D-Lite

[martianviking]

...Getting the chip from the Saturn is a different story since you'll probably be able to keep some of the resistors and caps intact...

It sounds like picking up a busted Saturn to start out with is definitely the way to go for maximum ease and reduction of total cost.  Now I suppose it's time to find some info on how to modify a Saturn motherboard to do what we need.

Thanks for the info, fragment.

[fragment]

since I couldn't find a dead saturn, I picked up a PSX 1001 and ripped that sucker out! D-lite said that you can use an oscillilator instead of a crystal for the clock. So to start off, what are we looking at for the following parts:

CXA1645 from a console: $5-15 for a dead Saturn, PSX 1001, 5001, 5501

Oscilliator:

LM1881N: - I know some of you will know this one

Caps, resistors and misc: probably another $8-15 (having to buy in bundles)

and of course, it will cost you alot of patience!  :blink:

[martianviking]

There also seems to be this kit, originally linked to by D-Lite:
http://akizukidenshi.com/catalog/items2.ph...1&page=#K-00018

It looks like the right kit (and at a cost of 2,600 yen it's pretty cheap), but I can't figure much more than that out from the page (I can't read Japanese and Babel Fish only gets you so far).

At this point I'm still thinking that modding a Saturn or PlayStation board would be the easiest and cheapest way.  I'm looking for instructions on how to do it and I will post anything that I find (of course).

[NFG]

Modding a saturn or playstation is easy.  Take the existing PCB, find the RGB and Sync input pins on the encoder and lift them from the PCB, attach your own input wires and you're done.

[DarthCloud]

I think that can help you if you are not allready found it berore

http://www.gamesx.com/rgbadd/cxa1645.pdf

[martianviking]

Thank you and thank you.  It looks like we have a winner in the "cheapest and easiest" contest.

But of course, I'm going to ask another question.    What would be the chances of success using a motherboard from a broken PlayStation 2 so that you could get composite, s-video, and component video (Y-Pb-Pr), depending on what cable you used?

[NFG]

AFAIK the PS2 uses a sony-custom encoder that has no pinout available, tho I confess I haven't looked into it for years.  I'd be prepared to write off the idea out of hand, but there's a chance I'm wrong.

[martianviking]

I see.  It would be handy to be able to make a cheap Y/Pb/Pr component video encoder out of all of the busted PS2 systems people have lying around, but I can see how that could be difficult without pinouts.

I guess the next thing to do is to try to figure out how and where exactly to supply power to a board made from a Saturn or PlayStation motherboard.  I just got a line on a busted SCPH-1001, so I should be able to to start actually fiddling around soon.

Thanks again to everybody for all the input so far.