I have DSO5072P and the rotating knobs stopped working, but everything else is working fine, only rotating knobs are not working. Push buttons work. I have checked the keyboard, also changed all the logical IC on the keyboard (74HC393, 74HC595, 2x 74HC4051), but the problem is still there. I am out of ideas what to do. Oscilloscope is 2,5years old, but was in use less than an hour in this time. After 2 years I powered it on and the knobs are not working.
I measured pin 1 and pin 2 of 74HC4051 U2, and there is noisy signal on one pin and almost nothing on the other pin. If I understand correctly it should be a nice square signal on both pins, with different phases?