I recently retrieved an old 800XL from my parents' attic, and have found that it's not working. I can't remember if it was like this when I put it away 25-ish years ago, but I had two of them and the definitely both worked at one point. The fault is a brownish coloured screen as soon as the computer is turned on, usually with scrambled-looking output in light brown to the right of the screen, though occasionally it ends up as one or two solid vertical bars of the cream / light brown colour. The attached photos show the output. It's a Rev. C board with all socketed chips. I've tried removing and reseating them all, but no joy.
I have a good bit of experience troubleshooting and repairing Amigas, but I'm starting from scratch with this, and I can't seem to find any schematics of the 800XL anywhere, which doesn't help matters. So far I've gotten as far as checking that the CPU clocks, which are both running, and the halt pin, which has regular pulses. To me, this would suggest that it's not able to reset properly for some reason, but I thought I'd ask and see if anyone has suggestions on where to look.