Red Screen Problems [XL/XE] - Fix Checklist

{From a now-defunct Atari board}

This is really a "sister thread" to the Black Screen Problems thread.

You'll find that much of the potential causes are the same and solutions will be a repeat...and in the same way as the "Black Screen" thread - it'll depend on whether your board is socketed or soldered.

What I'll do, is start with the "Red Screen" only stuff. (please refer to board pic below - (from old AAge thread))

1] Leave system running and check if any chips get hot (twenty mins) should be long enough REPLACE ANYTHING HOT. Nothing getting hot? proceed to next step

2] Look at swapping in/out Basic Rom with known good part.

3] If no change, then next try; CPU, MMU, OS Rom and finally Ram chips

3] The fact that you have a red screen means that GTIA is (at least) working at a very fundamental level) - but can still be faulty. Replace.

4] Is your display steady or does it flip/roll? If steady, then again Antic is managing to issue VSYNC commands - but may still be faulty. Replace.

5] Finally, 800XL Field Service Manual states a reddish/brown display may be U2-U5, 18, 19, 28, 30. Replace these.​

if NONE of the above works you'll need to refer to the "Black Screen" thread and work through it - ignoring anything you've already tried above.