Atari 800 S-Video Problem

[thom0707]

Hello,

 

I'm looking to solve an issue I am having with my Atari 800.

 

I bought an S-Video cable years ago off of eBay. It produces crisp video on my Atari 800, but the colors seem off. Additionally, bright colors seem to produce a ghosting effect. Please see my attached screenshot of River Raid. I'll also include a screenshot of Basic to show how characters look (A, M, N, and W in particular).

 

Any thoughts on what the problem is? With an RCA cable, I don't get the ghosting effect, but the colors still seem off. I have an 800XL and the colors look fine with this cable. It's been years since I've used these systems, and I never looked closely at the video output until now.

 

EDIT: In Basic, lowering the luminance of the text seems to help with the ghosting issue. Is there any way I can fix this at a hardware level?

 

Thanks in advance!

Edited February 17, 2018 by thom0707

[_The Doctor__]

Try a different cable, a different CRT, I had a toshiba that did that, it needed a bit of work, the bleeding and tearing was evident on television, and recording as well. Wasn't the computer at all.

https://www.repairfaq.org/sam/tvfaq.htm

http://www.e-repair.co.uk/tips.htm

If you find it's present from other sources hooked up to it, you may have delve into the set/monitor itself, be protected insulated and keep one hand out using fiberglass or plastic tools, check voltages and caps, this requires discharging everything inside the crt to be safe.

Eliminating those items it's time to dig into other causes.

Edited February 17, 2018 by _The Doctor__

[1050]

EDIT: In Basic, lowering the luminance of the text seems to help with the ghosting issue. Is there any way I can fix this at a hardware level?

Sure, you can construct a resistor network to cut

back on the level of luminance and/or chroma both.

Some insist on a 75 ohm resistor in line to 'match'

impedance to the TV/monitor but this is misapplied

#Fake News nonsense for RCA type connections in the

first place. Make it to be what works but understand

that it's probably only going to work with that

computer and that monitor both. Change one or the

other and the problem may show back up and in reverse

this time. 75 ohm inline wouldn't be a bad place to

start either. Which doesn't help any with the repeated

rumor that it's the only proper fix.

 

It's well known that the output levels of these

computers is quite variable, one is way to hot on

luminance and the next has chroma just a screaming.

 

Thanks in advance!

Most welcome - it's what we do.

[JR>]

Could the color differences be due to CTIA vs. GTIA? Do you know which chip your 800 has?

 

[BillC]

Could the color differences be due to CTIA vs. GTIA? Do you know which chip your 800 has?

 

I don't remember any color difference between the CTIA & GTIA, but is has been over 30 years since I have had a CTIA. The GTIA does have more video modes.

 

The color on the Atari computers can be adjusted via a potentiometer.

 

On the 800 this potentiometer is on the CPU card, and can be adjusted through a hole on the back of the RF shield when the cover for the RAM/OS card bay is removed.

[thom0707]

Try a different cable, a different CRT, I had a toshiba that did that, it needed a bit of work, the bleeding and tearing was evident on television, and recording as well. Wasn't the computer at all.

https://www.repairfaq.org/sam/tvfaq.htm

http://www.e-repair.co.uk/tips.htm

If you find it's present from other sources hooked up to it, you may have delve into the set/monitor itself, be protected insulated and keep one hand out using fiberglass or plastic tools, check voltages and caps, this requires discharging everything inside the crt to be safe.

Eliminating those items it's time to dig into other causes.

 

I found an another screen with an S-Video input. I didn't see the "ghosting" issue as much, but the discoloration was the same. My SNES seems to produce proper colors via S-Video.

 

Could the color differences be due to CTIA vs. GTIA? Do you know which chip your 800 has?

 

 

I'm not sure. How can I find out?

 

I don't remember any color difference between the CTIA & GTIA, but is has been over 30 years since I have had a CTIA. The GTIA does have more video modes.

 

The color on the Atari computers can be adjusted via a potentiometer.

 

On the 800 this potentiometer is on the CPU card, and can be adjusted through a hole on the back of the RF shield when the cover for the RAM/OS card bay is removed.

 

I'll see if adjusting that potentiometer helps. If so, I'll post before and after pictures.

 

Thanks!

[1050]

Could the color differences be due to CTIA vs. GTIA? Do you know which chip your 800 has?

I'm not sure. How can I find out?

 

I'm thinking by the part number on it.

https://www.atarimax.com/jindroush.atari.org/achgtia.html

 

When using google for our beloved Atari, I find it

best to include Atari in the search term to cut

down on worthless hits, but really CTIA wasn't hard

to search for...

 

http://www.atarimania.com/documents-atari-400-800-xl-xe-technical-documents_3_8.html

 

http://www.atarimania.com/list_documents_atari-400-800-xl-xe-_8.html

[JR>]

I'm not sure. How can I find out?

A few methods are mentioned in this thread.... http://atariage.com/forums/topic/80199-atari-800-ctia-or-gtia/?hl=+test%20+for%20+ctia