I have a semi-faulty AF Nikkor 50mm ƒ/1.8 lens (early non -S or -D model, with the focus distances in a little window) that has been having issues communicating with the camera. Both my F-801 and my D7500 will show "F--" for aperture data from time to time.
This lens had an unfortunate fall when I left my F-801 on a table inside a moving train while I left briefly. When I returned the camera had fallen. At the time everything kept working fine, and for another week there were no issues. However it now started having issues communicating the data back to the camera, with my D7500 thinking it is a non-CPU lens.
I've verified the issue is not the contacts, they're clean. I checked a disassembly video and realized the part I needed to check was easy to access. I then decided to inspect the interior of the mount ring. Nothing seemed off. My suspicion something had become dislodged was disproved as there was nothing to be misplaced.
However, I couldn't, for the life of me, figure out how the aperture is even being measured, and this is the focus of my question. There are no variable/sliding potentiometers or other mechanisms that engage with the aperture ring at all. There is a rocking cam that engages with the aperture lever in the camera, but that seems to have no contact with the electronics. As far as I can tell, the whole electronics section is completely self-contained. You can check for yourself in this video at 6:10.
Can anyone more familiar with these lenses explain how this works so I can hopefully diagnose this issue better? Thank you!