Killing a Nikkor AF-D lens cpu: whats behind a Micro-Nikkor 105mm f/2.8 AF-D internals?

This is a short Dunning-Kruger tale about an attempted repair of a Nikkor AF-D lens that was misreporting its max aperture and somehow killing the CPU - the dead CPU means that the DSLR body no longer recognises a CPU enabled lens which means no autofocusing (even on motor-enabled bodies), no metadata and no body controlled aperture - only dumb manual focus operations available.



How did it happen? I don't know and it shouldn't have happened as I've worked/repaired with fragile electronics for over 3 decades but yet here we are. A story of interest and what makes up the mechnical-CPU enabled internals of a Nikkor AF-D lens.

Cleaning Optics of a Micro-Nikkor 105mm f/2.8 AF-D

The 105mm macro lens has its origins in the 1960s and 1970s with the legendary 55mm macros and eventually deliverying its 105mm f/4 and f/2.8 variations from the lates 1970s into the mid 1980s . As with lenses of that era they were only capable of 1:2 reproduction ratio, even with the 1984 105mm f/2.8 AI-S. Work on the AF macro lens started in 1987 with full redesign (including optical rework) completed and release in 1990 with a priority to support autofocus and push the maximum reproduction ratio from 1:2 up to 1:1 (life-size) and eventually in 1993 the AF-D was released, with changes for the distance encoder

As with many old lenses cleaning of the optics might be necessary and the following appears to be only source to document front, middle and rear elements.