Atari 520 STf - Corrupted graphic and Red Screen with Diag Cart

[jurassicman]

Ok... I did find in a box a Null modem Cable lying around so I plugged it to my PC, installed minicom and actually it seems to work.

I did test the RAM and it's ok. When I did the test the color on the Atari monitor changed from Red to Blue (during test) to Green (once finished). Still no text on the monitor, though. Roms are ok as well and checking audio I can hear the sound (as i can when I load Lemmings). I also can see the colors on the Atari Monitor.

Which tests should I do?

minicom_01.jpg (73.23 KiB) Viewed 1465 times

[stephen_usher]

Run the internal tests, 'Z'

Given that the machine is doing this suggests that the machine is mostly fine but for some reason the SHIFTER isn't reading the memory.

[jurassicman]

Maybe this is the error...

minicom_02.jpg (74.62 KiB) Viewed 1463 times

[jurassicman]

Running internal tests ("Z") I get the same error.

minicom_03.jpg (65.49 KiB) Viewed 1461 times

[jurassicman]

I did some search on the Web and found some people with similar issues... it's not sure but it seems that the GLUE C025915-38A Chip could be, actually, the cause. What do you think?