Total failure instrument cluster after small repair

Good morning, together. On Sunday I switched the lighting behind the heaters because they had burned through. The next morning I found out that the complete instrument cluster is dead. Only the lighting went. Tacho, tachometer and the small display as well as the many small control lamps no longer go. My guess is that I must have solved a cable somewhere and in fact I found behind the heater a black wide plug without counterpart. I have disassembled half the dashboard – without success. Am I on the right track? Has anyone changed this lighting already and knows if there is anything on the plug or where it leads? I’m still going crazy Thank you for your help