If it is an "S" then 8V will be too high! Try 5,5V or a maximum of 6V...

Do you have the possibility to check the voltage on the extern power adaptor during the München board is working?

A pragmatical idea would be to integrate the HG440 Eprom into the MM IV module and play with Lyon power adaptor module. But this would be only a workaround and not a real solution.