Weird GTIA issue, perhaps UAV-related?

[pseudografx]

So yesterday I got my Atari 800XE back from a friend who added some upgrades for me - namely U1MB and UAV. I connected it all up and ran the "Atari Control Picture" binary. At first everything looked fine and I left it running for some while as I started doing something else. When I returned to my Atari, the color palette part of the picture was all wrong and it did the same when I reloaded the program. So I turned the computer off and let it cool down. Then, after a couple of minutes, I turned it on, reloaded the program and everything was fine again, until a little later. The picture gradually turns wrong. I am adding a video capture of the whole change.
Did anyone encounter a problem like this? Has anyone any suggestions for what's wrong? It seems to be temperature related, but nothing does get hot in the machine.

[_The Doctor__]

post pictures of his work on the mother board... could be gtia antic cpu 4050 or the uav itself... might have been statically zapped...hope fully it's just one of those problems and not all.. esd is no joke. ground yourself when the machine is open. Replace GTIA.

Edited February 5, 2021 by _The Doctor__

[+Nezgar]

Looks like you may have one of the infamous faulty late production PAL GTIA's. Maybe others can confirm if these symptoms match up?

 

@tf_hh made a simple PCB to "fix" the chip without having to replace it:

 

 

[_The Doctor__]

Thought the Faulty PAL produced a line gap in the middle of the shades of grey... or is the thought that the uav plus the faulty pal gtia chip has become cumulative?

[pseudografx]

Here is a couple of pictures of the board. It is definitely not the GTIA from the buggy batch, as 1) I have a Taiwanese 800XE, and 2) It has never happened before and I am using this very machine since 1990.

 

[_The Doctor__]

double check uav jumper shorts, is the 4050 still around?

check for crack in the traces/places where soldering was done.

if fully socketed machine before install check the pin alignment and the sockets... sometimes the swipes can not make perfect contact if the pins of a header or chip legs push in or out depending and temperature can cause the tension and connection to change in all such instances.

if all else fails remove uav, if all is good again, swap uav.

Edited February 5, 2021 by _The Doctor__

[pseudografx]

Thanks, will check.

[+tf_hh]

 

On 2/5/2021 at 4:48 PM, pseudografx said:

So yesterday I got my Atari 800XE back from a friend who added some upgrades for me - namely U1MB and UAV. I connected it all up and ran the "Atari Control Picture" binary. At first everything looked fine and I left it running for some while as I started doing something else. When I returned to my Atari, the color palette part of the picture was all wrong and it did the same when I reloaded the program. So I turned the computer off and let it cool down. Then, after a couple of minutes, I turned it on, reloaded the program and everything was fine again, until a little later. The picture gradually turns wrong. I am adding a video capture of the whole change. Did anyone encounter a problem like this? Has anyone any suggestions for what's wrong? It seems to be temperature related, but nothing does get hot in the machine.

 

Unfortunately I´ve encounter this behaviour several times, also without UAV. From my experience, this is a problem based on the combination of ANTIC and CPU used. After several tests I can deny any influence by the GTIA used, but changing the ANTIC to another working one can help in 90% of all cases. Sometimes the CPU must change. Both parts works fine in other systems...

 

 

[pseudografx]

Just remembered I should post a follow-up regarding this issue. It turned out that it wasn't the GTIA that was causing it, but a different chip. The issue was resolved by replacing the 74LS08 (U18) with a 74F08.