800XL S-Video mod - need help

[gmontag451]

I performed the 800XL S-Video mod (described here at post #8) remove C56, lift C54, connect R67/68 to chroma pin. I verified everything and checked continuity, but I'm getting a weird result:

 

On my TCL TV, the RF output is still in color but looks worse, and the AV input is snowy, high contrast B&W and rapidly scrolls.
On a portable LCD screen, the S-Video is clear but B&W. (My Apple IIe also displays in B&W on this screen.)

I know that some TVs just can't display video from older devices, but because the RF is still in color, I think I must have done something wrong. Can anyone suggest what to do next? If it matters, I'm powering the computer from a USB charger (5.3V 2A)

In a YouTube video (here) they also remove C55, should I be doing this?

Thanks for any help!

 

Edited August 1, 2021 by gmontag451
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[manterola]

Just two days ago, I did that same mod for an 800XL and it worked great. 

Recheck all your connections and be sure you are picking from  and removing the right components. 

I actually spent most of the time finding a "map" of the 800XL motherboard in order to find the locations. 

[gmontag451]

Here's my work, sorry the photos are a bit blurry. C54 is raised on the right side, and not touching anything else.
Hopefully you can see if I made a mistake? Is it possible that this particular mod leaves the RF color intact?

Edited August 1, 2021 by gmontag451

[Faicuai]

2 hours ago, gmontag451 said:

C54 is raised on the right side, and not touching anything else.
Hopefully you can see if I made a mistake?

Everything looks good in there.

 

Please, keep in mind that C54 is at the heart of L+C summation. Therefore, when lifting right-side. COMPOSITE output will NOT work, but s-video will (just better and cleaner).

 

One thing that you can try is bringing C54 right-side back in contact, while the system is on, and through the interface you tested above, and see if the image renders correctly.

 

 

[gmontag451]

I noticed that there was a buzzing sound on the TV, and it reminded me of the olden days when I occasionally accidentally plugged a video cable into a VCR's audio inputs, causing a loud buzz.

 

A quick Google search confirmed: TCL has a *proprietary* AV input adapter... Of course they do ? TCL's adapter feeds video through what would normally be ground, hence the buzzing sound.

 

I threw together some alligator clips to reverse the video signal and it worked, but the image was super saturated. So I reconnected C54 as you suggested and tweaked the trim pot R38. Now I have the correct color, but a blurry image with dark bands creeping up the screen.

 

Next I'll try removing C55 as shown in that YouTube video.

[gmontag451]

Removing C55 left me with no video, so I reinstalled it. ?‍♂️ Not sure why it's removed in the YT video.

Also, while reconnecting C54 makes the image much better on the TV, it becomes unusable on the LCD screen with vertical lines through the entire image.

Edited August 1, 2021 by gmontag451

[Titan.IO]

Hello all,

 

I have a PAL Atari 800XL and I applied the simple s-video mod. Problem is, after about 10 mins the colours start to randomly change. What the hell is going on? I turn off the power and on again and it resorts back to the correct blue colours. Can anyone help?

[xrbrevin]

you tried the colour trimpot? they can get crusty with age

[Beeblebrox]

This has been resolved - it's Attract mode (like a screen saver) - normal function  :

 

 

Edited May 9 by Beeblebrox