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SC1224 on 8-bit IN COLOR!


puppetmark

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I came across this board on e-bay:

eBay Auction -- Item Number: 1604095706091?ff3=2&pub=5574883395&toolid=10001&campid=5336500554&customid=&item=160409570609&mpt=[CACHEBUSTER]

 

And After an extensive e-mail conversation with the seller (who used to own an 800XL), decided it might make it possible to decode the 8-bit video to RGB. I hooked it up tonight, and it WORKS!

 

I connected it with the composite output from a stock 130XE. The picture looks quite good. I took a couple of pics:

 

post-9166-12844323423_thumb.jpg post-9166-128443235218_thumb.jpg post-9166-128443238312_thumb.jpg

 

The colors are actually brighter than my camera captured.

 

Here is some info on the board:

050415-NTSC+to+RGB+Converter+WP_201.pdf

 

I am running mine with a 9V 300ma wall plug adapter and II have the SC1224 Horizontal and Vertical sync inputs tied together and connected to the composite sync output on the board. the R, G ,B, and ground are just connected as expected.

 

There is more testing to do, like trying to get the C-Y output from the 8-bit to work instead of the composite, which may remove the slight dot crawl that I see. I am also going to test the super video mods. I would like to try and find separate H and V sync outputs instead of using the composite sync. The SC1224 is very forgiving about it's sync inputs, but some other monitors may not be. This board also actually supports PAL video as well, but it has been modded to "force" NTSC mode. The seller said he would explain how to un-mod the board, so It will detect a PAL input. I will post that info once I have it.

 

Eventhough there is a lot to experiment with on this board yet, but RGB converters are almost non-existent these days, so grab these boards before they are gone. It was very easy to get this working and it should be easy to mount the board in a project box. This may be the best way to finally get a matching monitor for our XE computers!

Edited by puppetmark
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Price looks OK.

 

Do you know what decoder IC it uses?

 

Chances are, it'll work just as well by feeding CSync from Atari into HSync, and just leaving VSync alone.

 

Is there any form of saturation control? One of those wish-list items for such a device was to be able to boost saturation dependant on luma level.

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Do you know what decoder IC it uses?

 

Chances are, it'll work just as well by feeding CSync from Atari into HSync, and just leaving VSync alone.

 

Is there any form of saturation control? One of those wish-list items for such a device was to be able to boost saturation dependant on luma level.

 

The decoder chip is a Sony CXA1950Q

 

The adjustable controls (pots):

 

Red Brighness

Green Brightness

Blue Briightness

 

Contrast

Sharpness

Color

Hue

 

There are a few others that have lock-tight on them and I haven't investigated those yet.

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Can you try some of my Interlace stuff... link in my tagline.

 

 

Sure. Good Idea. I ran an interlaced demo last night and I was impressed, no flickering but the scan lines were well defined, kind of a hard edge sort of thing. Still, very close to what my professional JVC composite montor outputs.

 

Definite interference in pic 2... here's hoping it'll look better running via seperate Chroma/Luma.

 

That cross hatch pattern in the picture isn't on the monitor, must be something with my digital camera. There is just a tiny bit of dot crawl.

 

 

 

Do you stick the decoder card into the monitor or into the A8

 

Right now it is laying on my workbench. The board is around 3 inches x 5 inches, and the delay lines stick up almost two inches, so it would be tough to put into an Atari or a monitor. I think a seperate box would be better.

Edited by puppetmark
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Woot! I got this board to work with S-video (the seperate chroma and luma outputs on the Atari). All that has to be done is to cut a jumper and solder the connections for C, Y and Ground. Turns out, This makes a big difference as suspected. There is no more interference! it is a very clean, clear picture. Its better than my professional JVC monitor which has S-video in! It's not as good as a monochrome TTL for 80 column text, but it's pretty close adn its looks amazing on games. The colors are very vibrant. the following testing was done in S-video from the Atari and with a stock 130XE. Taking accurate pictures of a CRT can be tricky, and some of these picture may look like there is a slight dot pattern on the screen, but that is just an anomaly from my camera, the picture has no banding at all. However, I think the pictures should give a good idea of how this is working:

 

post-9166-12845917387_thumb.jpg

This is how to connect the Chroma and Luma lines to the board. This will disable composite video, but a switch could be easily connected to switch between the two types of inputs

 

 

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Here we have flickerterm (all lines are straight and no flickering which makes sense since there is no scan doubling going on here, just RGB decoding), Alley Cat, and Preppie

 

 

post-9166-128459148506_thumb.jpg post-9166-128459150332_thumb.jpg post-9166-128459151466_thumb.jpg

LW does not look so great, but changing the background to black helped a lot. also, removing the color signal helped also. A color / BW switch could be installed for such purposes.

 

 

post-9166-12845915279_thumb.jpg post-9166-128459157587_thumb.jpg

I had to adjust the vertical size on the SC1224 to get the bottom scrolling text to appear. Stellar looks good too, but both of these have a motion blur from my camera.

Edited by puppetmark
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Hard to say if the interlace is working properly there.

 

I did find in testing that the vertical hold on older TVs could affect it to the point where it wouldn't work.

But it does work fine on my 1084s from VBXE's RGB.

 

I am fairy confident that it is. It just had to be adjusted. Is there something else to try in order to be sure? BTW, there is no flicker on the interlace stuff so far, unlike VGA scan converters.

Edited by puppetmark
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The smaller fonts in the Memopad demo should indicate if it's working or not.

 

The lines of pixels should be in distinctly seperate locations down the screen rather than flickering on the one location. I'm not sure if I included the special characters, but ones with sloping lines like / \ can help.

 

To get an idea of what I mean, running it in a recent Altirra version might help, since you can turn interlace on and off easily there.

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The lines of pixels should be in distinctly seperate locations down the screen rather than flickering on the one location. I'm not sure if I included the special characters, but ones with sloping lines like / \ can help.

 

To get an idea of what I mean, running it in a recent Altirra version might help, since you can turn interlace on and off easily there.

 

looks good to me. Its hard to get a picture of it but they look distinct and no flicker.

 

 

Also, I got this board to work on my SC1435 (NTSC) monitor as well! I didn't have to adjust the horizontal size as much and the bigger tube makes Last Word much more readable. The board hooks up easily. I had to do a bit of trial and error on the input pins and as it turns out, Pin 7 is actually composite sync in, even though some internet resources have pin 7 marked NC (not connected) on pinout diagrams.

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Thanks, I am very happy about it. I got a project box for the board today. It's even light grey colored - A bit lighter than the Atari grey but close.

 

Have you tried it with an SM124 yet? It might work out better to use the monochrome for apps and the color for games just like it was intended on the ST.

 

I have not but i doubt it will work anyway. The SM124 is a high resolution Monitor so it has a higher Horizontal frequency. The picture won't sync up.

Edited by puppetmark
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Here are a few pictures of my finished interface. I removed the C-video connector, and the molex pins for easier hookup. Also, I removed the yellow jumper wire which removes the power input from the on-board power jack, allowing me to mount my own on the case. The power input to the board is the connection closest to the voltage regulator vacated after removing the wire. The "extra" yellow wire going to the DIN plug is the audio out from the 8-bit, so I can use the internal speakers of the SC1224.

 

I chose a DIN jack for the output because they are easy to mount, It kind of follows what Atari did with much of there hardware, and this way I can make different cables for different monitors. Other than the LED and wire, parts came from MCM electronics . I really like the light gray case, probably good for other Atari projects. For anyone interested here are the part numbers:

 

6.5" x 4.13" x 2.09" Plastic enclosure [21-4830] $7.31

8 Pin Male DIN In-Line plug [27-675] $1.20

8 Pin DIN Socket Female [27-1620] $1.39

SPDT Mini 1/4" Mount Toggle Switch [26-575] $1.09

 

www.mcmelectronics.com

 

 

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Edited by puppetmark
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