Originally mib1+ with 7’ high screen was installed, so I thought it would be just swap these units. And almost everythink are working (I can listen radio and etc., all controls seems to be working) except screen. Screen is just black. I did vcds scan and vcds shows that Cable for video signal open circuit.
Any suggestions what could be wrong?
Its not. Your link is not showing an MLB MIB2, which would have an example part number 8W0 035 035, its showing x1 A3 8V MIB1 High and x1 MIB2 High unit with 8V1 and 8V0 part numbers. While the MIB units in general do share a lot of the same menu systems they are also very different, again your link is not showing an MLB A4/5 unit.
The screen needed for an MLB MIB2 High would be (example)8W8 919 605 and is a completely different resolution to the A3 8V screens. The control unit is also different. Photos of same A5 parts I have here from my test bench:
while they might look the same from behind the units are different. Firmware is different, the expected compatible supporting control modules are different, screens are different and even the units faceplate is different so it won't fit in the Audi A3 glovebox without whipping out a cutting tool.