Hello Hans and Walter!

Thank you both for your valuable informations!

It is the Lyon 68020 32 bit version.

I have repaired the button and now it works perfectly! The problem was exactly what Walter said. The button has a small metal plate inside and under the plate there was a lot of dirt.
When I took the module apart I saw that a big chip in upper left side of the chipboard (if the buttons are in lower right end) has a Lyon 32 bit V 207 text on it but there is a smaller chip just under the procesor with Portorose 32 text on it. Is this ok? Or did someone allready made modifications on the chipboard? I've seen that Portorose is the 1989 version of Mephisto computer.

Sorry for all the questions, I have only one more I played a couple of games yesterday and I noticed that b4 field sometimes doesn't recognise the figure on it. If you than put the figure again right on the center of the field, it is ok.
Is this possible to repair by myself? I do not see how to open the board to get to the magnetic sensors?

Thank you very much for your help!

Besr regards,
Blaz