8bit on VGA with S-video

[flashjazzcat]

Can anyone clarify the wiring diagram earlier in this topic? I'm totally stuck - still waiting for a cable in the post, and unable to get the information I need to modify my home made cable.

[puppetmark]

Can anyone clarify the wiring diagram earlier in this topic? I'm totally stuck - still waiting for a cable in the post, and unable to get the information I need to modify my home made cable.

 

Did you see this post?:

 

http://www.atariage.com/forums/index.php?s...mp;hl=LCD+Diode

[flashjazzcat]

Did you see this post?:

http://www.atariage.com/forums/index.php?s...mp;hl=LCD+Diode

Missed that one - thanks. Particularly fond of the post immediately after it.

[puppetmark]

Did you see this post?:

http://www.atariage.com/forums/index.php?s...mp;hl=LCD+Diode

Missed that one - thanks. Particularly fond of the post immediately after it.

 

Sure, No problem. When I get some time, I am going to combine the drawing in this thread, perhaps modifying it a bit, and the diode fix and do some testing.

[flashjazzcat]

When I get some time, I am going to combine the drawing in this thread, perhaps modifying it a bit, and the diode fix and do some testing.

I look forward to that. My cable is working now, but still with slight vertical banding. I believe this can be ironed out completely, though.

[flashjazzcat]

My replacement s-video cable finally arrived and it's marginally worse than the home-made one for vertcal banding. Can someone PLEASE explain how the 100p capacitor is fitted according to this diagram:

 

 

I could make the thing up in five minutes if I understood the diagram...

 

...uh... and what does a 100p capacitor look like?

Edited June 26, 2009 by flashjazzcat

[+bf2k+]

My replacement s-video cable finally arrived and it's marginally worse than the home-made one for vertcal banding. Can someone PLEASE explain how the 100p capacitor is fitted according to this diagram:

 

I understand most of it...

 

bottom of pot hooks to ground.. top of pot hooks to chroma

 

what does the right leg of the cap hook to?

Edited June 26, 2009 by bf2k+

[+bob1200xl]

The square box with the diagonal line thru it is a variable resistor. This will have three pins. The one in the middle is the output. The other two are the inputs, one to ground, one to the CHROMA pin.

 

Remove the wire from the CHROMA pin and connect it to the 100pf capacitor. The other end of the capacitor goes to the center pin of the variable resistor (called a 'pot' sometimes). One of the outer pins of the pot goes to ground and the other connects to the pin that you removed CHROMA from. Turn the shaft of the pot for the best picture.

 

100pfd capacitors look all kinds of ways - it just depends. They will be small (1cmx1cm or less) and have '100' on them.

 

Bob

 

 

 

My replacement s-video cable finally arrived and it's marginally worse than the home-made one for vertcal banding. Can someone PLEASE explain how the 100p capacitor is fitted according to this diagram:

 

 

I could make the thing up in five minutes if I understood the diagram...

 

...uh... and what does a 100p capacitor look like?

[flashjazzcat]

The square box with the diagonal line thru it is a variable resistor. This will have three pins. The one in the middle is the output. The other two are the inputs, one to ground, one to the CHROMA pin.

 

Remove the wire from the CHROMA pin and connect it to the 100pf capacitor. The other end of the capacitor goes to the center pin of the variable resistor (called a 'pot' sometimes). One of the outer pins of the pot goes to ground and the other connects to the pin that you removed CHROMA from. Turn the shaft of the pot for the best picture.

 

100pfd capacitors look all kinds of ways - it just depends. They will be small (1cmx1cm or less) and have '100' on them.

 

Bob

Thanks for taking the time to describe that, Bob. It's a terrific help.

[flashjazzcat]

Decided to mess around with the cable today, and these are the best results I managed:

 

 

 

After trying various components from the spares box, I found that the N5400 diode from the original ebay cable connected inline with a 220uf capacitor minimizes vertical banding in this case.

 

 

I'm going to try a higher rated capacitor next when I get hold of one. I might also try swapping the order of the diode and the capacitor. The pot can probably be removed since turning up the resistance does little to improve the picture.

[Jacques]

And? Any good news?

[flashjazzcat]

And? Any good news?

Not yet: been too busy with the LW beta this week to do anything with the cable. Unsure if I'll be able to improve it much, since there's no scientific theory behind my experiments! VBXE will alleviate my problems, anyway. I'll still try to fix the vertical banding on s-video in the meantime, though. Will report my findings...

[krupkaj]

It is interesting, what LCD are you using? Do you use stock XE or is there some super video installed?

[flashjazzcat]

It is interesting, what LCD are you using? Do you use stock XE or is there some super video installed?

Supervideo mod. Don't know if the banding would have been better or worse without it. Gonna try it with some different TV sets too.

[mojek]

Hello,

first excuse me, I am not good at electronics (just trying to learn something). I have bought an XL 800 and  XE 800 model by nostalgia reasons recently. But since beginning I am struggling to get a good picture on my LCD TV. using some offered cables at Czech and Polish sites. The cables are for the composite input and have been tried on a our newer LCD TV, then an older LCD TV (seen on the picture attached). These cables are obviously without any resistors,caps or diodes. The result was not satisfying - a blending with slightly green color and that specific vertical stripe on the left.  I think ,it could be caused by some non well functional components inside of the comps.

I recently got to an older LG TV with s-video input. I cannot recognize the schema of the cable - please can someone provide it?

 

Also, what is the suitable value of the variable resistor,  is it possible to use the diode labeled 1N5400? - you hopefully see it is obvious, that I am not so familiar with the diodes labeling....

And it also has been a longer time since the last post - has the solution been improved by chance meanwhile?  (Can e.g. the components be joined at the side of the TV/monitor s-video input.)

[Beeblebrox]

@mojekTwo great machines you've got there. 

 

These A/V composite/S-video display topics have been discussed many many times over the years and since this very old topic as you can imagine.

 

So firstly the composite cables will always have that bleed on modern LCD screens. Some worse than others depending on the machine itself, (eg not all XEs are created equally with some display outputs worse than others); plus also your TV and the cable being used will potentially affect the output futher.

 

In simple terms for stock output RF is the worse quality, then composite better and then S-video/Scart are generally considered the better/best.

(Incidentally there are many video mods and upgrades to give you amazing display output, (Sophia/Sophia 2/UAV/VBXE, etc etc), but I won't go into those now.)

 

There is a reason composite is a poorer image. S-video and Scart separate out the chroma and luma and will always be better than composite for the following reason:

 

T'internet Google search Quote: 

Composite video is an analog signal, and carries the video or picture through a single, low quality signal. In comparison, S-video carries the picture through two signals, namely the chroma (colour) and luma (luminance). This video signal is of far better quality than what composite video has to offer."

 

Good news is with the 800XE and generally the XE models you will be able to use S-video out the box.

 

With the 800XL if this is a stock 800XL which is likely (and not a Freddie chip equipt 800XLF), you won't and plugging in a DIN5 (your Atari's socket), to S-video cable will result in a black and white output. That is because back in the 80's Atari didn't hook up the Chroma signal inside the 800XLs as standard.

 

Luckly is is dead easy to hook it up yourself and costs next to nothing. See here: https://forums.atariage.com/topic/335123-first-post-first-800xl-advice-on-cleaning/?do=findComment&comment=5056326

 

Basically you connect a wire from the left side of the R67 and R68 resistors, (connect them both with a solder bridge), with a 100omh resistor in the cable then connect to pin 5 of the DIN. (You can also hook this up under the Pcb if you'd rather)

 

This simple mod restores Chroma and you can use an S-video cable.

 

If you have an 800XL with a freddie chip then you don't need to do this.

 

(

 

Cable wise myself and many others highly recommend this double shielded S-video cable btw:

http://herculesworkshop.com/cgi-bin/p/awtp-product.cgi?d=hercules-workshop&item=80304

 

Hercules workshop Din5 to S-video and DCA audio jack:

 

There are also on Ebay somewhere. Worth buying this cable even though they are based in Canada. (Postage costs to the UK in my case were very reasonable).

 

There are other mods you can do for the XE, (S.X.E for example):

****

 

BTW this futher mod for the stock 800XL will get rid of interferance and checkerboarding on an LCD screen when using an S-video cable and I'd highly recommend doing it whilst you are hooking up the Chroma:

https://forums.atariage.com/topic/345055-scart-s-video-cable-setup-atari-65xe130xe800xe800xl/?do=findComment&comment=5172850

All you are doing is lifting the right side of a particular resistor and (optionally) installing a switch. Dead easy.

 

Hope that is helpful?

 

Also as you are a returning Atarian earlier I'd posted the following info for another individual and so to save me posting it all here, I'll link to it:

 

Edited December 19, 2022 by Beeblebrox

[mojek]

@Beeblebrox

Thank you so much for the quick answer. 

I have chosen the solution (with some older components found at home).

 

 

The result is is definitely better , however as also mentioned by you, I can now recognize differences if using different computer or even LCD TV. 

1)I tried to build SCART cable from older VGA cable with kind of shield found on three needed wires, then there were two slightly less diameter wires  which one I used for

ground - that was not so much successful - similar output as for composite and one o my monitor shows in grayscale, and the second one again with similar shades.

2)I tried to build SCART cable from one already home made with four stand-alone well shielded wires -this finally gives better results (although not yet done with shield wiring at the SCART side exactly by the instructions  (this I think I can try a next time.)

I am going to try the s-video connector, I found the monitor with the s-video only "HD-Ready" though and I can spot some notable blending when typing in Basic, and after a short time it got to a slightly nicer picture)

 

once again many thanks for your quick and helpful info!

 

 

[_The Doctor__]

outer wire material is normally shield inner wire is normally signal. sheath of wire around all is normally double shield/ground depending...