=> mimo:
Lotharek is very busy man, I asked him many questions , but his answers are either laconic or: ''read the manual, everything is there, why don't You read it first, I know You didn't even read it so I will not waste my time anymore'' etc...
So NO, no help from Lotharek…
=> Stephen:
I think maybe I have found the problem: my CPU board is very noisy (I've switched to other CPU board and there is much less background noise)...
Worth to try is to take A4 and BELL signal from the nearest possible point, near POKEY chip, but directly from Atari 800 mainboard, not form the CPU and GTIA pins.
Anyone knows where to take those signals from?