Yes I find it no fun with a multimeter, but I have enjoyed the learning experience. I cannot detect the high low transition, assuming it is there. I will get a logic probe. I am very fond of STM's because of the lower profile and Mouse port is not in a stupid place. I assume there will never be a new board from Exxos that will fit in the smaller case., so will have to fix em.
I have no idea what an oscilloscope costs but my new Atari ST hobby had had me gripped for a few months now, we will see. Yes I checked the continuity through the whole set of rams chips, it made me dizzy at first following the schematic.
The layout I certainly found difficult to understand at first.
As far as what Frank said, that is what I did first because it sounds unlikely having 8 dead lines, but I can't find anything, but I haven't changed the chips. Anyway, part of the ram is damaged regardless of what other things are not right. I follow every suggestion that I receive.
Thanks.
When I next update the thread I will try to post a photo. Thanks.