I had a perfectly good, working 800xl until not long ago - I turned it on after not using ti for ages and I just got a black screen.
After googling and reading some of what you fine folks on here do to repair 800xls, I replaced all the rams with sockets and new 4164s.
I recapped the motherboard, just for the sake of removing those tired, old caps
I socketed the OS chip and burned a replacement - now I geta browny / red screen? I verified my new eprom to the code and also read out the original and verified it to the code and they report as being good (the same code) ???
I socketed the BASIC chip and left it out to see if the computer booted without it
I bought (yesterday) a working 65XE (nice boxed) and another working 800xl. I swapped over the working main ICs to no avail...
I'm now thinking about replacing the 2x 74LS158N ics near the ram, thinking they may not be controlling the RAM properly?
I'd really like to persevere and get this old boy going, I've had it a long while and still miffed it just died on me...