Need help with 800xl video

[Quiver]

Been reading all the wonderful things that people have been doing with the Atari, and all the great upgrades that makes my soldering iron hand twitch. So I dug up our family's first computer, an Atari 800xl and powered it up after inspecting the caps and such. Ah, the glorious READY prompt, but with a problem that was creeping in when we took this machine out of service in favor of an Intel 80386 machine with 4 Megs of ram. It almost appears as a color misalignment with a read flare around the cursor. In the test screens and games there also appears a dark ghost image shifted to the left of the screen. I've consulted the Field Service Manual and replaced U20,Q1,Q3, CR2, and CR3. The only thing I haven't replaced is U17, GITA, but I'm not convinced that it's the fault. If I adjust the color adjustment trimpot to give me grey scale I have a nice sharp display. When color is added is only when the fault appears. I have screen shots that better illustrate the problem. I will appreciate any help to get my old friend feeling better again.

[Mclaneinc]

Is that a composite or RF screen?

[Quiver]

Should have specified, sorry. This is from the composite output.

[Mclaneinc]

Not sure then, if it was RF it looked like a slightly off channel picture but comp, don't worry tho, loads of proper picture boffins on here, sadly composite is lousy anyway but not usually that bad..

 

Hope someone can help..

 

And as you have an itchy soldering hand I'm sure there's a nice project for you with various upgrades to the picture..

 

Also worth mentioning what TV system...Guessing from colours, NTSC

Edited November 22, 2019 by Mclaneinc

[Quiver]

TV system is an RCA composite to HDMI perverter, er converter box. Cable is actually a Sega Genesis model one composite cable. The only thing different in the cable is that video and audio is pin swapped. The TV standard is NTSC.

Edited November 22, 2019 by Quiver
TV standard

[Mclaneinc]

Pass...Its early evening here in the UK / EU so maybe guys will get back to you soon with USA folk later..We even have Australians (but don't tell anyone)

Edited November 22, 2019 by Mclaneinc

[+bob1200xl]

It looks like the LUMA is feeding the COMPOSITE input. What kind of video cable are you using? Try a different RCA connector.

 

If you feed LUMA into COMPOSITE, the monitor will do its best to find the CHROMA signal. There should not be any CHROMA in the signal but most Ataris have leaky video, so what is found is garbage. Looks terrible, like your pics.

 

Make sure you are feeding COMPOSITE into COMPOSITE.

 

Bob

 

[xrbrevin]

its always worth cleaning the colour trimpot, just in case its become a bit crusty during storage

do you have isopropyl alcohol?

Edited November 22, 2019 by xrbrevin

[Quiver]

Checking the pinouts on the cable that I'm using and the Atari, you just might have a point bob. Hrm, well I guess I need to test using the RF output then if that looks fine go buy a real Atari composite cable. If I recall correctly we started using the Genesis cable because the original broke, and it was darn all if we could find a replacement anywhere.

[TGB1718]

If your monitor can take S-Video, make one of those leads, the guys here tlod me about it as I was using composite and it was crappy,

made up the new cable and it's really good.

[Quiver]

So I need a real Atari video cable. RF output shows none of this issue. It does show gobs of snow and audio noise, but that is another matter.

[TGB1718]

Just check your video cable first, Composite Video is on Pin 3 and if you want to make an S-Video lead with seperate Phono plugs for sound

 

S-Video plug ============= Atari Plug

1 ------------------------------------- 2

 

2 ------------------------------------- 2

 

3 ------------------------------------- 1

 

4 ------------------------------------- 5

 

Audio

L ------------------------------------- 3

 

R ------------------------------------- 3

 

GND --------------------------------- 2

 

This is what I made

[mimo]

It could well be that HDMI perverter, the Atari signal is not to modern specs and devices like that as well as modern TVs can really struggle with the input.

Results vary from no signal to odd behaviour to excellent.

[Quiver]

I'm pretty sure that the cable I'm using is a major factor. Comparing the Genesis pinouts to the Atari pinouts it does appear that I'm connected to the composite luma of the Atari. I only have color by the grace of a poor design. This does make sense when I tested my 65xe and only had a black and white image on the screen. The 65xe may have less leakage. I should check that one out using the RF output just to be sure.

[BillC]

On 11/22/2019 at 11:06 AM, Quiver said:

Checking the pinouts on the cable that I'm using and the Atari, you just might have a point bob. Hrm, well I guess I need to test using the RF output then if that looks fine go buy a real Atari composite cable. If I recall correctly we started using the Genesis cable because the original broke, and it was darn all if we could find a replacement anywhere.

8bitclassics sells 5 video cables for the Atari 8-bits, 3 with additional connectors for monitors that support either S-video or separate Chroma/Luma. These are compatible with the Atari DIN5F monitor port, which is present on all but the 400/NTSC 600XL/XEGS.

 

They also sell a composite to HDMI signal converter, I don't know how good it is but haven't had any issues with the video cables I purchased from them.

 

Composite + dual mono audio

S-video + Composite + dual mono audio

Chroma + Luma + Composite + dual mono audio

 

https://www.8bitclassics.com/product-category/computers/atari-8-bit-computer/

[Rybags]

I'd just do the 5 minute mod to add chroma to the monitor port then get or make an S-Video cable and use that (assuming your TV has input for it)

 

Though it seems here at least that new TVs give you the best and the worst and omit all the stuff in the middle, ie inputs for RF, composite and HDMI only.