Getting S-Video from Minigun supergun

[mehguy]

I wanted to get S-Video out of the minigun supergun. Is it possible to use something like an AD725 or Sony CXA2075/CXA1145/CXA1645 video encoder (video encoders used in the Mega Drive and PS1)? Do these IC's expect the RGB signal coming straight from the arcade pcb or is it ok to feed the RGB output of the minigun (which is buffered with a THS7374) into one of these IC's?

[NewSchoolBoxer]

I don't touch arcade boards but I wanted to weigh in for lack of anyone else helping. Open to corrections or improvements.

The short answer is if your arcade boards output 15 kHz horizontal sync, this is a circuit you can build yourself. If 24 or 31 kHz, you need a specialized downscaler found here to drop the sync to 15 kHz that S-Video and Composite expect, as well as the corresponding RGB signals. Be aware that NTSC and PAL S-Video and Composite are not compatible with each other: http://scanlines.hazard-city.de/

15 kHz?

So we got the AD725, CXA2075 and additionally the BH7236AF encoder chips to choose from. More for older versions. Reading the specs sheets, they all expect TTL level sync inputs.

The THS7374 chip is used for console mods pushing to consumer television. Definitely looks like it outputs lower voltage 75 ohm sync so you need to step up to TTL. Extron devices do this, as does the LM1881 sync separator (though it would add noise being redundant).

NTSC and PAL signals for S-Video and Composite are different beyond just 60/50 Hz. Can read right on the AD725 specs page that Y and C carrier frequencies are lower in NTSC than for PAL. Each chip can output NTSC or PAL video based in pin configuration.

I see sub $3 AliExpress and Monoprice converters that I wouldn't trust. I assume they pull 5V from pin 9 of VGA but the parts alone to make such a converter cost more.

AD724/AD725
Our EU friends have an entire circuit for you to use and note the pin differences for NTSC versus PAL.
http://www.cpcwiki.eu/index.php/RGB_SVideo

Found the link from a site that shows an impressive amount of testing with shop link at the bottom. DIY kit (FOR PAL) at $22 USD:
https://retrohax.net/rgb4all-composite- ... eo-module/

The AD725 specs page's has a full recommended circuit for RGBS to S-Video and Composite. In fact, the above links seem to copy it 100%. Adds 75 ohm resistor and 0.1 uF (= 100 nF) capacitor on R, G and B input lines and leaves sync alone. Y, C and Composite output lines each have 75 ohm and 220 uF. The resistor is for impedance matching and capacitor is for AC coupling.

If you buy someone's completed kit then you don't need to know any of that, except if it's configured for NTSC or PAL. Should assume it outputs 75 ohm voltage level sync.

I see the Jrok Arcade RGB to Composite + S-Video Encoder has these limitations: (http://www.jrok.com/hardware/RGB.html)

To work with the unit, games MUST have:
15kHz horizontal line frequency. It is NOT designed for medium resolution games or for VGA cards.
Positive RGB output ( ie. black = 0 volts )
For example - Nintendo games such as Popeye, DK, DK Jr., DK3 and Mario Bros all use inverted video - these require a separate video inverter to work correctly.
Negative Standard Resolution composite sync. ( 15kHz horizontal line rate )

Also out of stock at every link.

[Josh128]

^

Nice post. Thanks.

[NewSchoolBoxer]

Thank you! Was afraid of a pro arcade modder coming in and saying I left out XYZ details and options. There were more things I wanted to add but I was less confident in the information.

The hazard-city link mentions the Extron VSC 700 but doesn't elaborate or mention the 700D model. These two are your all in one solution for 24-100 kHz. They convert RGBHV/RGBS/RsGB straight to Composite or S-Video or even Component on the D model! I don't really get why they skip 15 kHz but there are many options for that vsync. https://media.extron.com/public/downloa ... d_revC.pdf

AD723
European Antonio Villena uses the older model AD chip to convert VGA to S-Video and Composite with a switch for NSTC and PAL to boot. Actually has 3 in stock at €35 with no need for assembly. Doesn't specify the vysnc but from the AD chip we know is for 15 kHz only.
https://www.antoniovillena.es/store/pro ... o-adapter/

CXA2075
This chip is made by Sony and used in the Sega Genesis / Mega Drive 1. Has a feature to turn R and B into R-Y and B-Y for Component out as well. My Life in Gaming shows in their SNES video the Genesis RGB being superior. I found one downscaler not on the hazard-city link that uses CXA2075: Micomsoft XAV-2s

Micomsoft products are famous for two things in retro gaming: high quality and not being cheap. Also makes the Framemeister. The XAV-2s sure enough takes in RGB and outputs Composite and S-Video. I wasn't sure at first that its DSUB-15 (VGA) input could work on American computers versus Japanese. Seems the first DIP switch turned on is for the Japanese FM Towns computer and off is standard VGA, so we're good. Other input is for JP21. Also outputs stereo AV. I can't confirm if it's able to output PAL video though.
https://gamesx.com/wiki/doku.php?id=av:micomsoft_xav-2s

Giving credit where it's due, RetroRGB publicized the release of the RGB-2YC, which does what it sounds like: RGB to Composite and S-Video, at 15 kHz of course. Supports both PAL and NTSC with no less than 4 RGB inputs (only uses one at a time). I guess you pay for that convenience since it costs $90 + $35 shipping to the US. http://www.axunworks.com/RGB-to-Composi ... 41706.html

[Fudoh]

The Extron VSC machines are scan converters to convert from ED and HD to 15khz interlaced. Not what the OP is looking for. (the D model adds 15khz SDI output).

The CXA route is good for an internal mod. The new RGB to Composite/S-Video solution that bob recently showed (don't recall the name right now) seems like a good external add-on to any supergun that outputs RGB already.

[RGB0b]

There's actually three that I know of which should work, all listed in the post: https://www.retrorgb.com/will-light-gun ... video.html

I didn't show Mike's open source design in that video, cause I'd modified it to be part of my lag testing kit. I should probably buy another one, to have in these videos. All work similar in that RGB-to-S-Video should be fine, but composite will most likely give you problems with color.

[Fudoh]

Axunworks, right. Don't know why I can't seem to remember that. It looks like a really nice solution, I just simply don't have any use for it. Otherwise I would have gotten one already.

[NewSchoolBoxer]

Two legends building on my comments as I live and breathe. Thanks for explaining, I couldn't actually find specs stating if the mini supergun will take 24k or 31 kHz. The PCB demand must squarely be on 15 kHz. I glossed over the D model's Component being SDI. I guess the best uses of it are to the BVM A series where you don't have a BKM-68X or convert from HDMI. Found 900 and 900D VSC models listed on eBay but it seems 500/700 ones are the newest.

I looked at RetroRGB's page beforehand and watched the video. First link is Axumworks that I covered, second I didn't find any Composite/S-Video devices on the Linuxbot3000’s eBay shop. Bob does say in the video they usually don't have the downscaler in stock so can message the store. Third link is Mike Chi's device but I admit I read “15KHz VGA to SCART” adapter as RGB SCART and not Composite/S-Video over SCART.

Now actually clicking the link, VGA2NTSC uses AD725 to convert RGBS/RGBHV to NTSC Composite or S-Video as the name suggests. Rather than selling it, he released the design for free and links to an OSHPark PCB for $46.40. So no one making these products for the money. Also links to jft's GitHub link that adds a switch between NTSC and PAL and another for CSYNC and HV. Super cool but also not selling it.

Analog Devices including the completed circuit on the AD725 datasheet was genius. I'd like to try the CXA though as Fudoh suggests since the world has enough AD725 converters.

I didn't show Mike's open source design in that video, cause I'd modified it to be part of my lag testing kit.

Interested in future lag testing content.

[Fudoh]

you're right, sorry. Missed you mentioning the Axunworks. The name just didn't click, so I didn't associate it with what I saw on Bob's video before.

I also forgot that I have a Wega CRT sitting here (from before Sony bought the brand. One with the original design by Hartmut Esslinger). I wanted to get this running with some modern sources, so I might be getting the Axunworks after all.

[SnowCake]

Thank you! Was afraid of a pro arcade modder coming in and saying I left out XYZ details and options. There were more things I wanted to add but I was less confident in the information.

The hazard-city link mentions the Extron VSC 700 but doesn't elaborate or mention the 700D model. These two are your all in one solution for 24-100 kHz. They convert RGBHV/RGBS/RsGB straight to Composite or S-Video or even Component on the D model! I don't really get why they skip 15 kHz but there are many options for that vsync. https://media.extron.com/public/downloa ... d_revC.pdf

AD723 mcdvoice
European Antonio Villena uses the older model AD chip to convert VGA to S-Video and Composite with a switch for NSTC and PAL to boot. Actually has 3 in stock at €35 with no need for assembly. Doesn't specify the vysnc but from the AD chip we know is for 15 kHz only.
https://www.antoniovillena.es/store/pro ... o-adapter/

CXA2075
This chip is made by Sony and used in the Sega Genesis / Mega Drive 1. Has a feature to turn R and B into R-Y and B-Y for Component out as well. My Life in Gaming shows in their SNES video the Genesis RGB being superior. I found one downscaler not on the hazard-city link that uses CXA2075: Micomsoft XAV-2s

Micomsoft products are famous for two things in retro gaming: high quality and not being cheap. Also makes the Framemeister. The XAV-2s sure enough takes in RGB and outputs Composite and S-Video. I wasn't sure at first that its DSUB-15 (VGA) input could work on American computers versus Japanese. Seems the first DIP switch turned on is for the Japanese FM Towns computer and off is standard VGA, so we're good. Other input is for JP21. Also outputs stereo AV. I can't confirm if it's able to output PAL video though.
https://gamesx.com/wiki/doku.php?id=av:micomsoft_xav-2s

Giving credit where it's due, RetroRGB publicized the release of the RGB-2YC, which does what it sounds like: RGB to Composite and S-Video, at 15 kHz of course. Supports both PAL and NTSC with no less than 4 RGB inputs (only uses one at a time). I guess you pay for that convenience since it costs $90 + $35 shipping to the US. http://www.axunworks.com/RGB-to-Composi ... 41706.html

The THS7374 chip is used for console mods pushing to consumer television. Definitely looks like it outputs lower voltage 75 ohm sync so you need to step up to TTL. Extron devices do this, as does the LM1881 sync separator (though it would add noise being redundant).

NTSC and PAL signals for S-Video and Composite are different beyond just 60/50 Hz. Can read right on the AD725 specs page that Y and C carrier frequencies are lower in NTSC than for PAL. Each chip can output NTSC or PAL video based in pin configuration.