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krupkaj

8bit on VGA with S-video

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I have got new LCD LG M208WA. It is VGA with TV tuner and s-video input. I have tried it with several Ataris and it works nice with Jaguar, S-video modiffied VCS or ST.

 

But unfortunately there is a problem with 8bit machines. My XL with super video upgrade works very nice, but XE cannot synchronize on both composite and S-video. What is interesting it display very nice grayscale picture when Luma is connected to composite input. I made super video XE in that machine and it is still the same.

 

Maybe the super video XE shoud be fixed slighly but I am not expert in that technology. Has somebody similar experience?

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I have got new LCD LG M208WA. It is VGA with TV tuner and s-video input. I have tried it with several Ataris and it works nice with Jaguar, S-video modiffied VCS or ST.

 

But unfortunately there is a problem with 8bit machines. My XL with super video upgrade works very nice, but XE cannot synchronize on both composite and S-video. What is interesting it display very nice grayscale picture when Luma is connected to composite input. I made super video XE in that machine and it is still the same.

 

Maybe the super video XE shoud be fixed slighly but I am not expert in that technology. Has somebody similar experience?

I've had my new similar LCD aside ready and waiting for freetime to get around to doing the s-video mod on my XE. Your problem sounds worrying. How have you got it connected? your description is a bit unclear? Did you mean you have your XE in both composite and s-vid at the same time? or did you mean it doesnt work on either ?

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Luma gives a picture since it carries the sync pulses as well.

 

Maybe the chroma needs attenuating. A resistor in series maybe? I'm not exactly an expert, so maybe someone else could expand.

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I have a 15" monitor/LCD that won't sync to any old computer's output but it works fine with a VCR. Something is different about the Sync output of these machines that many of these monitors don't like.

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Virtually no old machines use interlace. They just output 312 lines (or 262) every frame (hence the blank lines between rows of pixels).

 

Also, they're often slightly off standard so far as frame rate or line rate, but most TVs don't have any problem with that.

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Virtually no old machines use interlace. They just output 312 lines (or 262) every frame (hence the blank lines between rows of pixels).

 

Also, they're often slightly off standard so far as frame rate or line rate, but most TVs don't have any problem with that.

A remember we discussed some issues a few months back in an older thread http://www.atariage.com/forums/index.php?s...105926&st=0 and here http://www.atariage.com/forums/index.php?s...p;#entry1271860 Did anyone have any success with upscalers? I remember reading a post (but cant find it now) for one which mentioned sorting the incorrect signals from older 8-bit computers or something like that... the product sounded good but i never heard if anyone tried it out? I gotta get my s-video mod done soon. the tft i bought was supposed to have "superior upscaling" so i'll see Edited by Tezz

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Virtually no old machines use interlace. They just output 312 lines (or 262) every frame (hence the blank lines between rows of pixels).

 

Also, they're often slightly off standard so far as frame rate or line rate, but most TVs don't have any problem with that.

 

That is correct. The atari does not interlace, both odd and even frames are the same. I think the problem is the horizontal scan rate that does not comply with the standard. Analog monitors and TVs will do just fine with this because they are looking for "signals" with a fairly wide margine of error, but Digital Tvs are looking to find specific information in the analog signal so it can clamp on it and convert it to a digital signal. If it can't find what it is looking for, then it can not build a picture.

 

There has been other threads on this forum about using LCD / VGA Tv's, monitors, and converter boxes with the 8-Bits. I have tried a few different devices and other have as well. The bottom line is that it's a crap shoot weather it will work or not. I believe it is possible to make some kind of conversion device but it's not an easy thing to do.

 

With all that said, I will take a look and see if I can figure out what the differences is between the XL and XE Signals are and if there is something that can be done.

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Hi folks, some of you seemed not to understand Jan's Problem, i'll try to clarify ...

 

Jan got a new LCD Display. It has composite video and S-Video (separte chroma/luma) inputs .The problem Jan is faced with : the screen works flawlessly with his 2600 (with S-Video mod), Jaguar, ST and an XL (with S-Video mod), but it doesn't work with his XE. It didn't work with the stock XE, neither does it after he did a S-Video mod to it.

 

ONLY the XE makes this kind of problem. The strange fact here is, if he connects the luma output of the problematic XE to the composite input of his LCD screen he does get a BW picture. This is normal since the luma signal carries the BW picture plus sync signal.

 

 

I'd guess the sync signal is a bit weak, or perhaps the chroma signal is picking up some clock signal which lets the LCD think it's out of sync.

 

Virtually no old machines use interlace. They just output 312 lines (or 262) every frame (hence the blank lines between rows of pixels).

Someone was able to explain it very detailed to me. A device putting out interlaced will give 312 lines in one frame, and 313 in the other frame. ANTIC (and almost all other machines of that age, even ST in low and mid res or a Jaguar) gives 312 lines in the one frame, and 312.5 in the next frame. Because the last line of the frame is a little period of time too short, a CRT TV or Monitor won't switch over to the next scanline but display the next frame on the same 312 scanlines as the frame before.

This works with all baseband CRT devices. Of course, a LCD works different, and not every LCD input digitizer does detect this mode of display correct. Anyway, this is not Jans problem. His LCD is capable of this mode.

 

 

Jan, do you get a stable BW picture if you connect only the Luma signal to the Luma input of your LCD's S-video input?

Edited by Beetle

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I've had my new similar LCD aside ready and waiting for freetime to get around to doing the s-video mod on my XE. Your problem sounds worrying. How have you got it connected? your description is a bit unclear? Did you mean you have your XE in both composite and s-vid at the same time? or did you mean it doesnt work on either ?

Both S-video and composite does not work. I tried both normal and XE with super video. But the XL with super video works nice,

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Jan, do you get a stable BW picture if you connect only the Luma signal to the Luma input of your LCD's S-video input?

Yes, I tried it with stock XE and it display nice grayscale picure.

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I have the LG M228WA LCD, which is basically the same as Krupkaj's, only a bit bigger. :)

My 600XL with the SuperVideo mod connected by a composite cable worked fine with it but 130XE doesn't (see the attached video). I believe Krupkaj has the same problem.

LCDn130XE.zip

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That looks over-saturated (weird, because my PAL 130XE if anything looks a bit undersaturated and washed out).

 

I don't know if a too strong chroma signal would cause problems, although the fact that Krupkaj's TV works fine with luma only might indicate it does.

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HDTVs have a lot more to do than old, analog sets. They must decide just what kind of signal is being fed to them and set up their displays accordingly. I have a JVC that is able to 'see' anything I feed it from an Atari, but my cheap(er) Sanyo does not. On the Sanyo, the component (Y) input doesn't 'hook up' with my 1200XL or 130XE. If you look at the VBLANK interval on the Atari 1200XL, you won't find HSYNC pulses. The GTIA puts them out but someone forgot to pull up pin 11 with a 1000 ohm resistor. I soldered one in, but it didn't help - the sync is now there - it just didn't fix the problem. The other problem with HSYNC during VBLANK is that the HSYNC rate should double in that time frame. On the Atari, it does not. This is a little harder to fix...

 

So, the Y component input has a very high bandwidth, but you can't be sure that just any HDTV will work on our Ataris.

 

You can use Y component on a CRT television but it doesn't really look any better than Y/C (s-video)

 

You should also add 75 ohm resistors to ground if you're driving a TV rather than a monitor. (which usually has built-in terminators) This is especially true for a stock 130XE.

 

So, a JVC 32E478 works OK (the picture is full of noise that you can't otherwise see on a low-definition display, but it is very sharp and detailed noise!)

 

A Sanyo DP19647 does not work (on Y component input)

 

Bob

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I played with this a little today. Somebody noticed it is possible that chroma is too strong, so I soldered resistor trim into the chroma. Now the monitor can synchronize and the picture is that:

post-2769-1194814442_thumb.jpg

Working value of resistor is around 1k. Then I add 100n capacitor into chroma. It is little better now, but not so much. So what should be still wrong?

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You should also add 75 ohm resistors to ground if you're driving a TV rather than a monitor. (which usually has built-in terminators) This is especially true for a stock 130XE.

 

Where do these go? From the chroma/luma wires to ground, or between the A8 ground and the TV's ground, or...?

 

What's the usual effect of missing terminators, on a regular analog CRT TV?

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I connected it like this:

post-2769-1194820868_thumb.png

and the result is this:

post-2769-1194820893_thumb.jpg

Edited by krupkaj

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just for info. I have just replaced the capacitor with smaller one (100p) and now my XE works with my LCD!! :)

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just for info. I have just replaced the capacitor with smaller one (100p) and now my XE works with my LCD!! :)

 

Can you post a "final" picture as to what you ended up with?

 

Did you make your resistor/capacitor addition internally in your Atari at the monitor jack? Or? Could you please add a little detail as to how you connected this?

And what final values did you end up with 1000 ohms + 100 pF?

 

Thanks,

Larry

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You should also add 75 ohm resistors to ground if you're driving a TV rather than a monitor. (which usually has built-in terminators) This is especially true for a stock 130XE.

 

Where do these go? From the chroma/luma wires to ground, or between the A8 ground and the TV's ground, or...?

 

What's the usual effect of missing terminators, on a regular analog CRT TV?

 

From the chroma/luma wires to ground - at the monitor end of the cable is best. No terminators allows more shadowing on the edges of characters and, in this case, too much signal at the jack. This overloads the input which may just cut off the signal inappropriately, like the sync tips.

 

Using a capacitor (100pf) on the chroma filters out the lower frequencies that you don't want anyway, and reduces the color signal itself.

 

Bob

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here are photos of current state. Both super video and standard XE sync without problem and displays similar picture, the ordinary XE has the vertical strips as usual (this is not so noticeable on photo) and the super video one has dark strip on the left edge.

This is from super video XE:

post-2769-1196103890_thumb.jpg

standard XE:

post-2769-1196103914_thumb.jpg

 

If you have any idea how to improove that let me know

Edited by krupkaj

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Krypkaj - could You make some pictures of Your connection cable modified plug ?

 

i still can`t make my LG working. Thnaks

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I have exactly the same vertical banding problem with a home-made s-video cable and since I don't understand even simple circuit diagrams I'm having trouble visualising where exactly the resistors and capacitors discussed here are supposed to go. I did have a cable ordered from ebay which had a diode inside the DIN plug, attached to the chroma pin, but since I dismantled and re-wired the plug I don't recall if the the diode was also soldered to the ground pin.

 

Since without the diode the vertical banding is a problem, I want to re-attach it inside the home-made cable. If I attach a wire between the diode and ground, should the ground jumper wire go to end of the diode attached to the chroma pin, or the other end of the diode (basically the s-video plug end of things)?

 

The lead as bought worked very well but the diode seems essential to a good picture with the equipment I'm using. Sadly the chroma line broke in the cable so I cannibalised the DIN plug and made my own cable, but I don't recall the exact wiring of the diode. I'm still waiting for a replacement from the manufacturer and I'm starting to wonder if it will ever arrive. :)

 

A photo of the inside of one of these leads would indeed be helpful.

Edited by flashjazzcat

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