S-Video Cable Issues

[RetroSpawn]

Hi all, 

 

I have constructed a S-Video cable according to the below schematics. I have swapped pins 5 and 1 around to eliminate the check board effect I'm getting as seen on the photo. If I connect one of the pins, I get black and white perfect video, when I connect the other one then the colour pops on the screen, but the check board shows up. Am I doing something wrong here? 

 

Edit Atari 65XE

Edited April 30, 2023 by RetroSpawn

[xrbrevin]

if its an 800XL, chroma is not connected as standard, you have to do a small mod to rig it up

[RetroSpawn]

4 minutes ago, xrbrevin said:

if its an 800XL, chroma is not connected as standard, you have to do a small mod to rig it up

My bad. It is an Atari 65XE.

[+kheller2]

What orientation are these jacks? Looking into the XE 5 pin jack and converting to a SV jack? And show your work. 😃. 

[xrbrevin]

here is a pinout of the monitor port and the Svideo plug for reference

 

 

[xrbrevin]

for XE, the current quick-fix for XE models is the "Simple XE Mod". here is the text and an image that shows the relevant components.

 

Replace R204 with a 68ohm 1/4W resistor

Replace R205 with an 820ohm 1/4W resistor

Bridge/jump R116

Add a short 24AWG or larger wire from pin 8 or 9 of the 4050 (U20) to a ground point near the RF modulator

 

ive done a few now and its my current favourite for XEs.

the issue is that theree wasnt an industry standard for monitors back then and each manufacturer did things differently.

[Nezgar]

I'd also test the picture on a real CRT that supports S-Video... Some LCD monitors don't support S-Video properly, and may only do weird things like process it as composite, etc.

[RetroSpawn]

24 minutes ago, kheller2 said:

What orientation are these jacks? Looking into the XE 5 pin jack and converting to a SV jack? And show your work. 😃. 

I have since destroyed the finished cable and soldered temporary wires onto all the pins of the MONITOR OUT, to work out which one works.

Hence my work is a temporary bunch of wires as below:

 

 

I get the black and white video in very good quality when I only run 1 wire, but when I add the 'colour' wire I have full screen covered with zig zags.

21 minutes ago, xrbrevin said:

here is a pinout of the monitor port and the Svideo plug for reference

 

 

I have noticed your pinout stats 'if you get vertical zigzag lines...', which is basically what I have I guess? Looking at the 'colour' screenshot I posted above, it definitely looks like zig zag lines across the whole screen!

I reckon the ground is connected as I tested the cable multiple times with a multimeter and since destroyed it and redone with temporary wires as seen above. Not sure on how to proceed. Would that mean the ground continuity between the port and the motherboard is not OK?

 

 

18 minutes ago, xrbrevin said:

for XE, the current quick-fix for XE models is the "Simple XE Mod". here is the text and an image that shows the relevant components.

 

Replace R204 with a 68ohm 1/4W resistor

Replace R205 with an 820ohm 1/4W resistor

Bridge/jump R116

Add a short 24AWG or larger wire from pin 8 or 9 of the 4050 (U20) to a ground point near the RF modulator

 

ive done a few now and its my current favourite for XEs.

the issue is that theree wasnt an industry standard for monitors back then and each manufacturer did things differently.

That is what I had planned after I get the S-Video cable to work OK, but I get the zig zag lines across the screen.

I have the scope ready to measure the signal values, but I can't proceed to this stage to replace resistors until I resolve the picture quality issue.

 

[RetroSpawn]

10 minutes ago, Nezgar said:

I'd also test the picture on a real CRT that supports S-Video... Some LCD monitors don't support S-Video properly, and may only do weird things like process it as composite, etc.

This is a good point. Unfortunately I have no way to test on a different TV. I have a CRT here, but it only offers RF and Scart eh.

[TGB1718]

1 hour ago, RetroSpawn said:

when I connect the other one then the colour pops on the screen, but the check board shows up. Am I doing something wrong here? 

I would think poor shielding on the cable, the best cable to use is individually shielded wires otherwise there's

a lot of crosstalk. There's no substitute for a decent cable as so many people here have found out when buying

cheaper cables.

[RetroSpawn]

Is anyone selling a good quality this type of cable in the UK by any chance?

Edited April 30, 2023 by RetroSpawn

[Paul Westphal]

Try the S video cable from 8 bit  Classics. It works without any mod, but you might actually have to wiggle it a bit to get it to work.

[RetroSpawn]

3 minutes ago, Paul Westphal said:

Try the S video cable from 8 bit  Classics. It works without any mod, but you might actually have to wiggle it a bit to get it to work.

Got a cable on order. In the meantime I will try to get a signal readings from the oscilloscope and make some improvements there. 

Thanks! 

[_The Doctor__]

This can be either lack of individually shielding on the Luma and Chroma lines, or a bad and missing ground on/withing the cable.

You need individual shields on both luma and chroma as well as cable shield around the two. This is called double shielding.

Only the signal wire shields terminate on both ends, the cable itself can simply terminate on the Atari chassis side ground and need not terminate on the other end.

[Beeblebrox]

11 hours ago, RetroSpawn said:

This is a good point. Unfortunately I have no way to test on a different TV. I have a CRT here, but it only offers RF and Scart eh.

I know it's not ideal and could introduce inteferance, (but at least you'd be able to test if you get your colour output with it) - you could get this to give you S-video to scart on your CRT TV:

 

[Paul Westphal]

On 4/30/2023 at 2:11 PM, RetroSpawn said:

Got a cable on order. In the meantime I will try to get a signal readings from the oscilloscope and make some improvements there. 

Thanks! 

I just saw this. If you could post your findings, it would be most appreciated!

[RetroSpawn]

12 hours ago, Paul Westphal said:

I just saw this. If you could post your findings, it would be most appreciated!

No worries. Still awaiting the cable from Germany. Unfortunately I didn't get the time to open up the Atari. 

 

I also got thick, individually shielded 4 core Cable and svideo to scart converter, so basically I will try to test all the possible tips from all the good people above. 

 

The only thing I have done so far is test my temporary s video cable on the converter.  The video is way better through scart port than through s video port 🤔

 

I will post more when I get around to do everything else. 

Edited May 6, 2023 by RetroSpawn

[Simius]

You can try to.connect pin 4 of the DIN connector to the ground on the MB and use it to separate color and luminance grounds. Contact resistance of the common ground is enough to a bad picture. 

[RetroSpawn]

Good tip. The cable I got has 4 cores, individually shielded, so can actually do that. At some point this year I will move onto VBXL if the outcomes won't satisfy me 😉

[RetroSpawn]

I had some time last night and completed the Simple XE Video Output Mod as per TheRetroChannel. 

I don't have the s-video cable yet and the only thing I was using for testing was a composite video cable with an optional scart converter.

Unfortunately my Pico 2202 refused to work! I wasn't able to grab another scope from somewhere so quick, so I went without taking the readings.

I plan to measure the signals next week, when I get a replacement.

 

The cable used looks like this:

Before I have done the Simple XE Video mod, I took a photo of the composite output on a Samsung TV through composite input.

After the Simple XE Video mod on an old Samsung TV through composite input.

 

After the Simple XE Video mod on a better Sony W905A TV through composite input.

 

After the Simple XE Video mod on a Samsung TV through scart converter.

Unfortunately my crappy s-video cable renders super crap image, but I will see how the 'good quality' cable compares when I get it next week.

Additional Self Test screenshot with artifacts. Sony W905A through composite input.

It looks pretty bad.

Next.

 

Awaiting a 'proper' s-video 4 pin cable from Germany to test it.

Measuring signals after the Simple XE Video mod I have done.

Robbing a bank to afford Sophia 2 or VBXE.

 

[mimo]

what power supply are you using?
I seem to remember seeing those zigzag lines before and it was a noisy USB power supply.
Might not be the issue or the whole issue here, but thought I would mention it 

[Beeblebrox]

Power could be contributing, but I suspect it's a combo of cable, grounding or other issues with the simple video XE mod. 

 

I did the same mod on several XE's in 2021..

See here:

 

 

 

[RetroSpawn]

44 minutes ago, mimo said:

what power supply are you using?
I seem to remember seeing those zigzag lines before and it was a noisy USB power supply.
Might not be the issue or the whole issue here, but thought I would mention it 

I have tested the original PSU + Sony USB PSU + Meanwell 5V PSU. All three resulted in the same results. That would rule the power supply out I guess?

18 minutes ago, Beeblebrox said:

Power could be contributing, but I suspect it's a combo of cable, grounding or other issues with the simple video XE mod. 

 

I did the same mod on several XE's in 2021..

See here:

 

 

Thanks for that. The thing is, I had the same 'quality' before the mod. The mod only increased brightness and sharpness, which made the whole thing look so much worse. I will now go through your link to see if I can find anything.

 

[Beeblebrox]

10 minutes ago, RetroSpawn said:

I have tested the original PSU + Sony USB PSU + Meanwell 5V PSU. All three resulted in the same results. That would rule the power supply out I guess?

 

Sure. Have a look at grounding, the wires, wire length and routing internally and also have a look at the thread I posted above. Aside my own experience (where I had a good result overall), that thread had a ton of info. The XE lines are generally worse that the XL lines. At least definitely the case with a PAL systems in my experience.

 

XE lines had poor pcb layouts when it came to the video circuits if I recall reading that correctly, and used cheaper materials and components from the factory as the production years went on and Atari tried to cut costs.

Imho and many others, the stock output from the 600XL for example is very good. The great thing is we have the likes of UAV, UGV, (latter very cheap to buy), Spectre, and of course Sophia 2.

 

Check out my UGV installs:

 

 

Edited May 9, 2023 by Beeblebrox

[RetroSpawn]

You're very helpful. What so you think about Spectre? Should I just abandon the troubleshooting and get that instead? It's very well priced in the UK.