Ricky Spanish Posted April 6 Share Posted April 6 (edited) This is @Atari8man2004 clown rasta. I turned on my 'cold' 1200XL, loaded the .XEX and some of the yellow and most of the grays was bright green. After some time, it changed to yellow/grays that you see here. Does that indicate a problem with some chips ? Mods in sig. Thanks. Edited April 6 by Ricky Spanish grammar sucks ha-ha Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted April 6 Share Posted April 6 (edited) No it does not indicate a chip problem, it takes approx 15 minutes for many older machines to warm up and color to settle. The only things that can be done to lessen such affects are high quality cap and transistors in the video circuit if the swing is too great, as that sometimes corrects degraded output. It is perfectly normal and part of the adjustment steps outlined by almost all computers of that era. If your power supply swings or changes too much from cold to 15 twenty minutes or the video transistors vary too much then you can look to touching or shoring that up. But chances are it's just the normal shift that occurs as the components warm up. This happens in the video chips themselves as well and is the nature of the chips. So there is only so much you can do, as outlined. It is normal. You can bump the color pot to keep it from being so very bright green at start but not so much as to throw the yellow off when warm. Edited April 6 by _The Doctor__ 2 1 Quote Link to comment Share on other sites More sharing options...
Beeblebrox Posted April 6 Share Posted April 6 I've seen this happen on an Atari 7800 also. Never really noticed it on my a8s, but no doubt it occurs.. 1 Quote Link to comment Share on other sites More sharing options...
+CharlieChaplin Posted April 6 Share Posted April 6 There are even demos showing effects when GTIA is heating up. (One is a GTIA temperature picture, for PAL Ataris, in degrees Celsius and a must see; unsure how it looks in NTSC) And the nice test program ACP (Atari Control Picture) also shows a nice / not so nice effect, when GTIA is heating up... GTIATEMP.ATR 2 1 Quote Link to comment Share on other sites More sharing options...
+mytek Posted April 6 Share Posted April 6 I attributed the problem to the color trim pot adjust circuit, and specifically a shift in the 5V power that feeds it. In the 1088XLD and 576NUC+ I used a precision thermally compensated zener diode to supply the color trim pot. And as far as I recall it works very well, with minimal thermal drift. Another method would be to use a high quality stable 5V power supply to feed your Atari - maybe a MeanWell PSU. 3 1 Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted April 6 Share Posted April 6 Hang a good meter on pin 17 of the GTIA and see if the voltage drifts around as the computer warms up. 2 1 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted April 6 Share Posted April 6 3 hours ago, mytek said: I attributed the problem to the color trim pot adjust circuit, and specifically a shift in the 5V power that feeds it. In the 1088XLD and 576NUC+ I used a precision thermally compensated zener diode to supply the color trim pot. And as far as I recall it works very well, with minimal thermal drift. Another method would be to use a high quality stable 5V power supply to feed your Atari - maybe a MeanWell PSU. retrofit that into the other Atari's forgot about that one. Quote Link to comment Share on other sites More sharing options...
Ricky Spanish Posted April 7 Author Share Posted April 7 Thanks for the replies. I tried that program, got to 55 in under 3 mins. 1 Quote Link to comment Share on other sites More sharing options...
Ricky Spanish Posted April 7 Author Share Posted April 7 observation #2 Different scenarios definitely take longer/shorter to 'warm-up'. The above ATR, didn't notice any changes whatsoever from 'cold'. The clown RASTA, took about 10-15 mins to settle in from 'cold'. atari8man Cleopatra RASTA took over an hour from 'cold'. All the games I tried, didn't notice any difference from 'cold'. Quote Link to comment Share on other sites More sharing options...
+CharlieChaplin Posted April 7 Share Posted April 7 Try ACP 1.0 by TeBe or ACP 1.1 by MDA (both programs are packed). After a few minutes stripes appear in the picture, then more and more stripes, until the picture looks "somewhat different"... I have one 800XL in my collection where this GTIA warm up happens very fast, while the other four 800XL take quite a long time. Maybe I should test A8 games with APAC pics (Kick Off, Winter Events, Cygnus XI, etc.) with the one computer that warms up very fast and see if it produces some strange effects there ? Or some other picture formats besides Rasta (Gr. 9, 10, 11, e.g. Apac, Apac-2, Paint 256, Pryzm, Escal Paint, HIP, RIP, TIP, etc.)... ACP10.xex ACP11.xex Quote Link to comment Share on other sites More sharing options...
Ricky Spanish Posted April 8 Author Share Posted April 8 2 hours ago, CharlieChaplin said: Try ACP 1.0 by TeBe or ACP 1.1 by MDA (both programs are packed). Hey thanks for that. Here's a couple pics, 1 hour apart. Quote Link to comment Share on other sites More sharing options...
+CharlieChaplin Posted April 8 Share Posted April 8 Well, I see no changes, just strange colours (maybe normal for NTSC, since I have PAL I do not know)... Here is what happens on one of my Ataris when the GTIA does warm up with ACP 1.0. picture 0 - computer cold, normal look (PAL), via S-Video picture 1 after approx. 45 - 60 minutes stripes appear: picture 2, a minute later, many more stripes picture 3, two minutes later, almost finished picture 4, a minute later, finish screen (does not change anymore, not even hours later) please ignore that picture 0 is much darker and all others are much brighter (and show mirror effects), I opened the roller blind / roller shutter... ahem. In the finish picture it looks like 16 colours each with 4 lum - but repeated four times (i.e. lum 0-3 are the same as lum 4-7 and the same as lum 8-B and the same as lum C-F)... strange eh ? Besides, ACP 1.1 (which displays 16 colours but each with only 8 lumas) shows the same effect on this computer! (All pictures taken with my cheap smartphone.) 1 Quote Link to comment Share on other sites More sharing options...
Ricky Spanish Posted April 8 Author Share Posted April 8 Weird. Definitely didn't see any of that with mine. I was never good at taking pics of TV/monitor screens haha. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted April 8 Share Posted April 8 That is not how any of my machines have ever looked. Very Strange Charlie. Quote Link to comment Share on other sites More sharing options...
351cougar Posted April 9 Share Posted April 9 once it gets to the final state try some freeze spray on different chips. see if the effect suddenly goes away Quote Link to comment Share on other sites More sharing options...
phaeron Posted April 9 Share Posted April 9 That looks like a GTIA timing problem. GTIA needs to combine two color clocks to form a 4-bit pixel, and it looks like as that machine warms up GTIA's timing goes bad and it's sampling the same 2-bit value twice. If you look closely you can also see that the color tile boundaries have shifted right by a color clock. 2 1 Quote Link to comment Share on other sites More sharing options...
drac030 Posted April 9 Share Posted April 9 17 hours ago, CharlieChaplin said: Here is what happens on one of my Ataris when the GTIA does warm up with ACP 1.0. Bad GTIA, type 2: http://atariki.krap.pl/index.php/GTIA#Wadliwe_GTIA 5 Quote Link to comment Share on other sites More sharing options...
pseudografx Posted April 9 Share Posted April 9 23 hours ago, CharlieChaplin said: Well, I see no changes, just strange colours (maybe normal for NTSC, since I have PAL I do not know)... Check my thread from 2021. It was not a bad GTIA. The solution is in the last post. 3 Quote Link to comment Share on other sites More sharing options...
+CharlieChaplin Posted April 10 Share Posted April 10 So I checked my other four Atari 800XL computers yesterday and today by simply running/displaying ACP 1.0 for six hours. The picture of ACP did not change on any of these four computers, so it looks like they do not have this "bug", like my 5th Atari shown above. Next thing to do is checking if the faulty Atari nr. 5 has a) a bad GTIA, b) a bad Antic (or another chip) or c) if a replacement of 74LS08 with 74F08 is enough to get rid of that "bug". Quote Link to comment Share on other sites More sharing options...
Ricky Spanish Posted April 10 Author Share Posted April 10 Weird that it does it with some programs, but no others. You figure it'd be all or nothing. Quote Link to comment Share on other sites More sharing options...
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