I got this Tesa Modul electronic lenght measuring instrument and 2 inductive probes to go with it. However it didn't work at all after powering it up. After disassembly I found a charred resistor inside, which actually seemed to still function, however the tantalum cap next to it was shorted to ground. I replaced the cap, but left the resistor be, since it seemed to have quite an exact resistance of 130 ohms. The instrument now somewhat works with both channels, but the ranges aren't quite right. Even with the smallest range the scale only moves a single interval (in this range 0.1um) after totally pressing the probe in, which is half a cm or so. There's a knob per channel for +/-, which is supposed to change the direction to which the scale should move, for maths with the two probe inputs. This works, so the signal must be getting atleast somewhere properly. The offset is also pretty random, and the knob for it doesn't seem to work.
The weird thing is that I couldn't really find any symmetry across the pcb to differentiate the channels, which means most of the stuff there is probably common for both the channels. This might explain why the channels behave the same.
I went around checking the transistors' voltage drops and didn't really find anything out of the ordinary. Furthermore, there's a 741 opamp and MC1439G opamp, the rest is mostly caps and resistors.
Is it possible to somehow find out what the charred resistor's value is supposed to be? What else is there to look for?