Here is an other update ... my keyboard is now acting very strange.
Since the other day Ctrl + Amiga + Amiga worked fine I decided to try it again yesterday and ... It did not work!
However something strange is that the Caps-lock button light flashed green and then off again. When I pressed it it did not want to turn green. I restarted the computer and Caps-lock started working again.
I tried pressing Ctrl + Amiga + Amiga again and again I had the same symptoms mentioned above. However this time I did not switch it off. After a few seconds (maybe half a minute) the Caps-lock flashed again and started working normally.
I therefore tried it for the third time. Again I got the same symptoms after pressing Ctrl + Amiga + Amiga. However this time the whole keyboard did not want to work! Again I switched off the computer; left it off for some time and switched it on again ... everything worked fine again.
It seems that the problems only start after pressing Ctrl + Amiga + Amiga! I still did not change the transistor. However does the above scenario make it clear that the transistor is the problem?
Regards,
Sim085