After a longer break we gave it another try and soldered the rainbow cable to the display of another scale. This time we were very careful and did only use as much solder as was really needed. After reassembling the scale the display still worked! Also the oscilloscope is displaying logic data, so the first step is done:

TODO: image of rainbow cable on the back of the scale

Now it's time to find the COM lines. First we need to find out which kind of LCD we have. The Display looks lilke this:

We have about ~80 segments but only about 19 data pins on the display. Therefore we clearly have a multiplexed display with multiple backplanes, which is controlled by so called COM-Lines. The question is now, how many COM lines we have. We also need to find out which Bias and Duty is used.

TOOD: images of COM lines