code 10100011b (I think) then a space then either code 1100011b or 11100011b then a space then code 10100011b and so on all across the screen and repeated on every line so the screen looks like vertical columns of half blocks (bottom half lit) then space then bottom row lit then space and so on.
I am really running out of ideas on this one. The screen output is regular and the same every time which rules out loads of options. No chips are running hot or cold.
Quick thanks to hlide for all his advice so far and mz-80a (Ben) for burning me a replacement M-ROM.
Hurry up or I shall be bald from pulling my hair out!!
