Thank you very much for the hint. I´ve been able to get the reading from TP601, this is OK and as it should. The next test point TP602 shows just nothing or nonsense. The PCB however is the one without any component descriptions and the parts displacement is slightly different from the schematic. This is massively frustrating. Also the disassembly is impossible without complete desoldering of all leads and switches. This is just nightmare to work on! I don´t think I´ll be able to fix this one, since I don´t understand where the TP601 signal should lead to and I can´t even look at the part side of the PCB properly to inspect the components. I think I´ll just have to move on and let it be.
