Intellivision ntsc rgb mod design help

[emerson]

I was looking into rgb mods for the intellivision and besides the RetroRGB mod kit there isn't much available for ntsc models. I discovered a pal mod circuit here which requires 3 bits for red, green and blue, which ntsc models don't have. Instead, ntsc models have a 4bit code (one nibble for each background color) and the AY-3-8915 does all the color processing. My goal is to design a decoder circuit which takes the 4bit color code and convert it into the 3 bits per color rgb code. To do this I need to know the 3bit rgb codes for each background color so I can design the decoder.

 

Does anyone have a pal intellivision service manual with the rgb color table?

 

Would someone with a pal intellivision be willing to open it up and measure the rgb bits on the LM1886 for each background color? I have included a test rom and truth table for anyone willing to help me out.

 

Thank you!

intv_rgb_color_test.zip

[mr_me]

I don't have a pal intellivision but I wonder how accurate that digital rgb data might be. I only say this because that digital rgb goes through an analog pal conversion, which looks different than an ntsc intellivision.

 

Maybe you've seen this, but there is an internal mattel document that has the yiq colour information sent to their hong kong manufacturer.

 

http://papaintellivision.com/pdfs/CCF10242011_00001.pdf

Edited November 9, 2018 by mr_me

[emerson]

I have not seen that document so thank you posting it! The color code table is in the ntsc service manual, but the yiq table is new information for me. Now to figure out how to use it...

 

I've read that pal and ntsc intellivisions have color differences so I would assume my proposed method would produce the pal color scheme. I want to say dark greens come out brown but I don't remember what else. Maybe the digital rgb codes could be tweaked to help correct this?

 

I came up with a somewhat cumbersome method of guess and check to try and figure out the rgb color codes. What are your thoughts on this approach:

 

- Set my rgb modded crt next to my Commodore 1702

- mod the Solarfox av circuit to handle two outputs or just build two of them

- feed the composite video into both monitors so the 1702 displays the desired color and the rgb modded crt has the necessary sync signals

- assemble the pal rgb DAC and feed the rgb output signals into the modded crt while the input signals are connected to DIP switches

- manually configure the DIP switches and compare the colors between the two monitors

[mr_me]

That's assuming the digital rgb colours remain consistent after going through the analog pal conversion.

 

The guess and check method might work better. Whatever you come up with someone will probably disagree with it. The important thing is the colours are distinguishable. E.g. tan vs yellow vs orange; red vs magenta.

 

I should have posted a link to this discussion.

http://atariage.com/forums/topic/278354-gfx-palette-flag/page-1

Edited November 11, 2018 by mr_me

[emerson]

Wow, I'm glad you posted that link. I should be able to use one of those palettes as a reference. Once again I thank you.

 

Whatever you come up with someone will probably disagree with it.

 

True that, haha. Plus, it isn't my intent to sell a kit or anything, this is just for a one off arcade cabinet I plan to build in the future. I'll post my findings once I get parts ordered and do some testing.

[emerson]

Here is an update.

 

Using the DIP switches to control the rgb lines did not work for me. The signals needed to be switched on and off with the sync signal and can't just stay in a constant state, so I tied the AY-3-8915 bit0 to blue bit0, bit1 to red bit0, and bit2 to green bit0 to produce the image below. The screen on the left is a Commodore 1702 and the screen on the right is a Sony Trinitron KV-13M40 with an rgb mod. Given this is just the LSB influencing the screen colors, they seem match the bits in the AY-3-8915 color table.

 

I'll give another update once the CPLDs arrive in the mail.

 

Left: composite Right: rgb

 

Commodore 1702 (composite)

 

Sony Trinitron KV-13M40 (rgb)

 

The breadboard

 

The "Solarfox Stack"

[emerson]

I had some free time today to sit and work on this more. I spent some time toggling bits around and came up with what I think is a decent palette. Since I removed the rf modulator the channel switch is now able to select one of two palettes.The switch could be useful for selecting between pal/ntsc palettes or whatever you want really. I also replaced the transistors from the pal circuit with a N2563 video amplifier. Below are pictures of how it looks. The pictures with two screenshots are comparing composite (left side) and rgb (right side). Both composite and rgb images are on the modded sony trinitron. The colors are a little darker in the pictures but you get the idea.

 

schematic:

 

breadboard:

 

my color test:

 

tennis:

 

tennis color test:

 

microsurgeon:

 

pitfall:

 

dracula:

 

frogger:

[SiLic0ne t0aD]

That looks great! I really need to dive back into my Inty RGB mod that I started & tried to install a while back. I have one of the retroRGB/Fred K. kits installed but something isn't working right and was never able to get it to display anything. I may have goofed up wiring up the mini DIN connector though, but I'll have to double check all my work. Unfortunately, it doesn't work with an OSSC due to some timing issues IIRC, so a different scaler/converter needs to be used and unfortunately, I don't have a Framemeister or else it would work fine with that, but I do have a cheap scaler from ebay which was also recommended. I'll be using this on a flat panel HDTV after all, at least for now.. but I do have a few CRTs, however they're not RGB modded or anything.

 

If I can't figure out whats wrong, I sure hope you do sell a few kits. Id buy one, since it would be nice to have an alternative option. It's sad that there's presently not any Inty RGB solutions out there.

[emerson]

That looks great! I really need to dive back into my Inty RGB mod that I started & tried to install a while back. I have one of the retroRGB/Fred K. kits installed but something isn't working right and was never able to get it to display anything. I may have goofed up wiring up the mini DIN connector though, but I'll have to double check all my work. Unfortunately, it doesn't work with an OSSC due to some timing issues IIRC, so a different scaler/converter needs to be used and unfortunately, I don't have a Framemeister or else it would work fine with that, but I do have a cheap scaler from ebay which was also recommended. I'll be using this on a flat panel HDTV after all, at least for now.. but I do have a few CRTs, however they're not RGB modded or anything.

 

If I can't figure out whats wrong, I sure hope you do sell a few kits. Id buy one, since it would be nice to have an alternative option. It's sad that there's presently not any Inty RGB solutions out there.

 

Is an OSSC similar to a Framemeister? I've never heard of it... I don't have a Framemeister either but it would be nice to know if it will accept an RGB signal with composite video as the sync source.

[mr_me]

See specifications here.

https://www.videogameperfection.com/products/open-source-converter/

 

They are similar except the framemeister processes by frame and ossc processes by line.

[emerson]

So it looks like the OSSC will accept RGB + cvideo sync through its SCART connector, but who's to say if it will have the timing issues mentioned earlier...

[SiLic0ne t0aD]

So it looks like the OSSC will accept RGB + cvideo sync through its SCART connector, but who's to say if it will have the timing issues mentioned earlier...

It's relatively issue free (actually proven, tested by retroRGB, etc).. I really like it. The OSSC is essentially a line doubler and has no extra image processing, unlike the Framemeister, so it's lag free.. A much cheaper, and possibly better alternative. I haven't messed with SCART cables yet but I use the VGA port on it mainly, for ColecoVision and Dreamcast. I tried using the component input but I think my Wii looks a little better plugged straight into my 43" Vizio HDTV. I will be using SCART soon though, when I RGB mod my n64 and SNES.

[emerson]

It's relatively issue free (actually proven, tested by retroRGB, etc).. I really like it. The OSSC is essentially a line doubler and has no extra image processing, unlike the Framemeister, so it's lag free.. A much cheaper, and possibly better alternative. I haven't messed with SCART cables yet but I use the VGA port on it mainly, for ColecoVision and Dreamcast. I tried using the component input but I think my Wii looks a little better plugged straight into my 43" Vizio HDTV. I will be using SCART soon though, when I RGB mod my n64 and SNES.

 

So RGB + cvideo sync is proven with the OSSC through SCART, nice! From the spec page, the OSSC also supports composite sync at the vga input which is useful. I'm curious if you could inject cvideo into the composite sync of the vga and have it work or if the extra video information will interfere with the sync processing...

[SiLic0ne t0aD]

So RGB + cvideo sync is proven with the OSSC through SCART, nice! From the spec page, the OSSC also supports composite sync at the vga input which is useful. I'm curious if you could inject cvideo into the composite sync of the vga and have it work or if the extra video information will interfere with the sync processing...

Hmm, I'm not too sure as far as injecting extra video information in there. I'm no wizard when it comes to video processing, that's for sure.

I'm pretty much a noob when it comes to Rgb, though I understand understand some of the basics, but anything beyond that is still a little over my head at the moment. I just tinker around with things but I need to study up on Rgb again, for upcoming projects.

[emerson]

This is my first RGB console mod truth be told, and I only modded my Trinitron so I would work on projects like this and learn more about RGB.

[SiLic0ne t0aD]

Right on! You gotta start somewhere.

 

I'd like to try Rgb modding one of my CRTs someday too, and I already have a 27" Trinitron KV-27FS120 that would probably be the ideal candidate for such a thing. I already have some Crt experience, so no worries there.. I've partially recapped my 36" Toshiba, which fixed a shutdown/overheating problem it had and I've been inside one of my Vectrex's several times to fine tune the picture, debuzz and recap the integrator circuit. Anyways, I'll stay tuned to this thread to keep up on progress.. Things are looking good so far! :thumbsup :

[rayik]

I really need to dive back into my Inty RGB mod that I started & tried to install a while back. I have one of the retroRGB/Fred K. kits installed but something isn't working right and was never able to get it to display anything. I may have goofed up wiring up the mini DIN connector though, but I'll have to double check all my work.

You might want too double check the wiring. I installed that kit and it works great.

[SiLic0ne t0aD]

You might want too double check the wiring. I installed that kit and it works great.

Well, that's exactly what I did tonight and I got it working. Woo hoo!

As I suspected, I made an error on the mini DIN connector, which I replaced and rewired.. I think I had the Sync and +5 lines switched around. Though it looks great, it still pisses me off that I can't use my OSSC and am forced to use a cheap Chinese converter. However, if Emerson gets his version finished and available to the public, I'll switch over to that since palates will probably be an option, along with stereo sound.

 

[emerson]

Nice work! If you can plug that SCART cable into a Sega Genesis model 2 and it works then the cable will be compatible with my mod as well.

 

As far as palette switching goes, the two default palettes will be the standard NTSC palette and a palette with colors that better match what they're called in the datasheet. The palettes are switchable with the channel switch and if you have a TL866 programmer you can download WinCUPL and create your own palettes. I think it would be cool to have a collection of palettes created by everyone uploaded here. Then people could pick which they like best and update their firmware.

 

I'm putting the finishing touches on the pcb now so hopefully I can get in the garage soon and make a prototype board.

[emerson]

I did a bit of research and it looks like a standard VGA port requires RGB signals at 0.7Vp-p with sync signals at TTL levels. Therefore, I would assume injecting composite video into the sync pin on the OSSC will not work. Looks like a job for the LM1881.

 

 

Edit: Here is an excerpt from the OSSC documentation

 

The AV3 input is a VGA/HD-15 connector which supports video in RGBHV, RGBS (pin 13), RGsB and YPbPr formats. RGBHV and RGBS modes require clean TTL-level sync signals and cannot extract sync from composite video or luma. AV3 is best suited for high-quality input sources as video LPF functionality is limited (the AV1 and AV2 inputs are routed through a dedicated LPF chip). Therefore, it is generally recommended to connect older consoles and arcade boards to these other inputs.

Edited January 25, 2019 by emerson

[emerson]

A quick update. I've finalized the pcb design and am ready to make some prototypes. I decided to make two different circuit boards based on the needs of the end user. Some of the features include:

 

- either mini din9 (RGB + C video) or dsub15 + 3.5mm audio out (rgb only) for AV output

- stereo audio with optional blend knob and/or dual mono switch

- the channel switch selects between two different palettes

- optional switch to select either TTL or attenuated composite sync signal (stripped from composite video via LM1881)

- optional switch to select the 0.015uF capacitor in the solarfox composite video circuit

- all unused pins of the GAL22V10 are connected to solder pads for end user development

 

Parts are in the mail now and I will give another update once I get things working.

[SiLic0ne t0aD]

Awesome! This sounds like quite the project. I hope everything turns out well and I'm sure it will. Fingers crossed.

[emerson]

Success! I now have a working prototype for the mini din9 board. When I was creating the footprint for the mini din9 connector I was measuring the pins from the bottom but assigning pin numbers from the top, therefore reversing the pinout and rendering my first board useless. Well, it actually worked fine, it just didn't follow the Sega Genesis model 2 pinout.

 

However, my second board works well. Currently there are female pin headers where the wires will be soldered. That allows me to work on the board without having to desolder a bunch of stuff. I decided to omit the voltage regulator and just pull +5v from the mainboard, it just runs too hot. Below are some pictures of the board and a staged install. I don't want to solder it in until I make the dsub 15 board.

 

I should receive the scart to hdmi scaler I ordered in about a week or so and just received my Genesis model 2 rgb scart cable, so I will post some pictures of that when it arrives to demonstrate sega pinout compatibility. I will also post pictures of the dsub 15 board when I get that built. Once I'm comfortable with both boards I will have them made professionally then begin work on the mod instructions.

 

The ptototype

 

Top side

 

Bottom side

 

The alignment is almost perfect!

 

The black line on the left will cut off the +12v leg

[SiLic0ne t0aD]

Nice work, Emerson!

Looks like some very tricky soldering on the bottom there with those SMD components.

Is the old channel switch on the bottom of the console still going to be used for swapping palettes?

[emerson]

The soldering did take a few hours with a pencil iron and thin solder. It's a little ugly because I had to pull the parts from the old board and most of the SMD parts still had solder on them. And yes, the channel switch still swaps the palette.