Quick update - opened up the 10K Operating System cart and reseated the chips in there (thanks for clarifying, Rybags) and cleaned the contacts better since having better access. Then once installed, I tried running it with just 1 memory cart. Same thing - no luck. Then I tried swapping memory carts / inserting them in different slots. Same thing. The only difference I noticed is if I didn't have a memory cart in the slot next to the OS cart( ie - OS cart, empty slot, memory cart) - I got nothing - no blue screen. I also tried just keeping it on for a few minutes to see if any error would appear. Nothing - just the blue screen with the solid cursor.... When I get more time I'll open it up and take a peek inside.
On a better note, included with the 800 was a 130XE - and it appears to be working fine - turning on to BASIC (although it scared me - when I first tried it, I got the same blue screen as the 800 - but after a few seconds it goes to the Ready prompt).
With the 130XE, I now have (working) an A400, A600XL, A800XL and now the A130XE. Hopefully I can get that A800 working!
thanks again
Chris