Atari 800 picture issues

[gs80065xe]

I purchased an Atari 800 last April. Everything appears to work. But the display is not as good as my 65XE. Text has a reddish tint. And Pack Man is missing pixels on the horizontal lines of playfield. So, I saw that it was suggested to replace R189 with a 220ohm resistor. I did that. Picture may be better. And adjusting the TV picture mode, got rid of the red tint in Basic. But Pac Man is still missing pixels. See attached images. I've tried different composite cables and TVs. Even tried the RF connection.

 

Could someone who has a perfectly working 800 with unmodified video hardware tell me if there's looks the same? The horizontal lines on my 65 XE are solid like the veritable lines. 

 

I was thinking about replacing the CPU Board. But Bradley at Best Electronics wanted to try some other things first. So we reseated the OS, RAM and CPU boards. At the same time, I pressed the ICs to make sure they were firmly in their sockets.

 

I noticed the OS board is modified. See here :

 

Bradley suggested we start by trying a stock OS board. So I'm going to try that. But I suspect Antic or GTIA.

 

 

[gs80065xe]

Anyone? Just need to confirm if your 800 displays the PacMan boarder the same as mine. My memory says my first 800 didn't.

[TGB1718]

Maybe it's my failing old eyesight, but I can't see any missing pixels in the photo

[jamm]

I can't get to my 800 at the moment, but if you look for "Atari 800 Pac-Man" videos on YouTube, you'll see that none of them look like the pictures you posted.  So it does look like something isn't correct.  Have you tried other games/programs to confirm that it isn't just a weird version of Pac-Man you're using?

 

Also - are you sure it's not just an issue with your display?  How are you connected to that monitor (composite/svideo)? 

 

Oops - I just saw that you did try different TV's and output methods.  Forget that suggestion!

Edited March 18, 2020 by jamm

[gs80065xe]

The 800 and PacMan videos on Youtube look like what my 65XE shows. The horizontal lines appear to be solid blue lines. My 800 has dots. But the vertical lines are solid.

 

I've tried 2 different composite cables and the RF connection. And two different displays. But the fact that the 65XE looks correct and Youtube shows 800 players look like the 65XE, something must be wrong with the 800. I think the video circuitry. It's too consistent on the entire board. Only the horizontal lines are wrong. So I doubt it's bad RAM.

[xrbrevin]

do you have another GTIA chip you can try?

[gs80065xe]

No. I was going to purchase a new CPU board from Best. But we're going to try replacing the OS board. Apparently mine is modified for some RAM upgrade. Can you still find GTIA chips for sale somewhere?

 

Edited March 18, 2020 by gs80065xe

[Sugarland]

That's a beautiful 800!!  Yes the GTIA is suspect. And just because you tried two different TV's doesn't preclude them. The 800 and 65XE do not output an identical video signal. Have you tried a CRT? Modern LCD's interpret the signal and they are often not very good at it, especially more recent displays are apparently not prioritizing composite signal quality since those devices are becoming more and more uncommon.

[xrbrevin]

you could always 'borrow' the one from the 65XE but it will likely require desoldering and XE boards are delicate in that regard..

[gs80065xe]

I no longer own any CRT's Recently tried to get a Commodore monitor off Craigslist. But it was snatched quickly.

[+DrVenkman]

Pretty sure you're seeing the effect of an analog display being upscaled (not very well) on a flatscreen. Too bad you don't have a CRT to check with.

[+Stephen]

Yeah - I agree it looks like it's more of an issue with the display(s) being used and not the 800.  I seem to recall the 800's video signal is "hot" (over voltage specs).

[gs80065xe]

I’ll need to see what I can do about getting a CRT. 

 

By the signal being hot, are you referring to its luma output? If so, I did replace R189 with a 220ohm resistor has described in a few other threads I read here.

Edited March 18, 2020 by gs80065xe

[Faicuai]

On 3/15/2020 at 7:16 PM, gs80065xe said:

I purchased an Atari 800 last April. Everything appears to work. But the display is not as good as my 65XE. Text has a reddish tint. And Pack Man is missing pixels on the horizontal lines of playfield. So, I saw that it was suggested to replace R189 with a 220ohm resistor. I did that. Picture may be better. And adjusting the TV picture mode, got rid of the red tint in Basic. But Pac Man is still missing pixels. See attached images. I've tried different composite cables and TVs. Even tried the RF connection.

 

Could someone who has a perfectly working 800 with unmodified video hardware tell me if there's looks the same? The horizontal lines on my 65 XE are solid like the veritable lines. 

 

I was thinking about replacing the CPU Board. But Bradley at Best Electronics wanted to try some other things first. So we reseated the OS, RAM and CPU boards. At the same time, I pressed the ICs to make sure they were firmly in their sockets.

 

I noticed the OS board is modified. See here :

 

Bradley suggested we start by trying a stock OS board. So I'm going to try that. But I suspect Antic or GTIA.

 

 

Just finished double-checking on my end, here.

 

There is nothing wrong with either your 800 or your display.

 

It seems you are seeing a very similar effect to "dot-crawl", which is a by-product of the [composite-to-component] video-decode function of your display.  I am 99% sure that those images do not come from s-Video but, instead, composite output of your 800 being fed to your TV / Screen. The solution is just to feed Y/C (sVideo) output from your 800, provided that your TV offers sVideo inputs (which most nowadays DO NOT, unfortunately).

 

sVideo:

 

Composite:

 

 

 

There is also the issue of most modern screens, or vide-processing engines handling substantially higher video-bandwidth than most CRT screens can decode, thus exacerbating these artifacts. I can see it on my DVDO iScan HD+ processor, also: composite shows the dots on chroma detail, but none via sVideo.

 

And don't worry about getting a CRT, because (apart from the "speed of light" factor" or the scanlines-structured matrix) you will be missing little else regarding usable bandwidth, distortion, linearity, black-point level, color gamut, resolution mapping, frame-rate conversion, time-base correction and, most importantly, final price (when everything is said and done).

 

Cheers!

 

Edited March 19, 2020 by Faicuai

[gs80065xe]

5 minutes ago, Faicuai said:

Just finished double-checking on my end, here.

 

There is nothing wrong with either your 800 or your display.

 

It seems you are seeing a very similar effect to "dot-crawl", which is a by-product of the [composite-to-component] video-decode function of your display.  I am 99% sure that those images do not come from s-Video but, instead, composite output of your 800 being fed to your TV / Screen. The solution is just to feed Y/C (sVideo) output from your 800, provided that your TV offers sVideo inputs (which most nowadays DO NOT, unfortunately).

 

Yes, I'm using composite video. But RF had the same effect. And, my 65XE looks fine. But the video circuits between the two are different. 

 

The display only supports RF, composite video and HDMI. It lacks component and S video.

[Faicuai]

Just now, gs80065xe said:

Yes, I'm using composite video. But RF had the same effect. And, my 65XE looks fine. But the video circuits between the two are different. 

 

The display only supports RF, composite video and HDMI. It lacks component and S video.

Yes, RF should be pretty close to Composite, as well.

 

I would bet that either a) Your 65XE must likely outputs lower chroma-resolution than your 800, or b) your 800 chroma-signal levels are coming out much higher / stronger than the 65XE, though.

 

Generally speaking, if you are going to be displaying your Atari's output in digital-displays, it would be healthy to separate the video-decode function completely (out of the TV) and run it on a dedicated piece of HW, with highest possible bandwidth on video-decode and then video-output / scaling functions. 

 

If you prefer an old-school CRT as your display of choice, you will need a pro-grade monitor (like Sony PVM) in order to get decent bandwidth, as well as good linearity, good color gamut and (most importantly) a good / deeper black-point level, which 99% of the CRTs out there for this purpose pretty much miss, badly).

[gs80065xe]

What about using a composite to HDMI converter. I think I have one.

[gs80065xe]

You're correct. It is the composite video. Using an composite to HDMI converter fixes the dot crawl. But the picture is not very good. Even on the 65XE. But this was an ultra cheap HDMI converter I got from Amazona  few years ago. I'll buy a better one.

[shoestring]

I get the same "reddish" tint on my 800 plugged into the LCD but it looks fantastic on my Sony PVM and other CRTs.

[gs80065xe]

13 minutes ago, shoestring said:

I get the same "reddish" tint on my 800 plugged into the LCD but it looks fantastic on my Sony PVM and other CRTs.

I was able to get rid of it. I had the picture mode on gaming. Cycled though until I found a good one. 

[gs80065xe]

I tried another RCA to HDMI converter. I think it’s the same one used below. But the picture quality was only a little better than the first converter The composite connection is the best picture on both machines. I’ll live with the dot-crawl on the 800. And the 800 picture is better since replacing R189 with a 220ohm resistor. 

 

Thanks for the help.