Mercedes Benz Sound 4000 from inside

Mercedes original car radio from 1998. Too new, but still the first original Mercedes radio in my collection. The repair needed a lot of time, some liquid or the like had dripped on the leg of the processor and gone under the processor. Electrically created additional resistance, which was not there when measured with the tester, but disturbed so that the Volume button did not work. Everything works fine now. 4 x 7W audio amplifier.