Author Topic: alternative option for CPU  (Read 846 times)

Bern

  • NG Member
  • *
  • Posts: 89
  • You ARE NikonGear
alternative option for CPU
« on: September 18, 2023, 15:42:52 »
Hi all,

I have a couple of "dead" for parts only Nikkor lying around and was wondering if the CPU in them can be repurposed for use in manual focus Nikkor.

I have the following

28-70mm f3.5-4.5
35-80mm f3.5-4.5
24-120mm f3.5-5.6
28-80mm f3.3-5.6

The target donor manual Nikkor would be

28mm f3.5
35-135mm f3.5-4.5
35-105mm f3.5-4.5

Any tips on how this can be done?


Keep shooting,
Bern

Birna Rørslett

  • Global Moderator
  • **
  • Posts: 5418
  • A lesser fierce bear of the North
Re: alternative option for CPU
« Reply #1 on: September 18, 2023, 18:12:55 »
The CPUs can be "reprogrammed"  by short-circuiting the lanes coupled to the moving brush for focal length (on the zooms) at various points. You will be able to lock the max. aperture in roughly 1/3 EV steps.

The problem is of course  you might get the max.aperture reading and by sheer luck the minimum as well, however the focal length typically will be wrong for the receiving host lens. An even bigger issue in practice is getting sufficient room for the CPU print board inside the receiving lens. Those old CPU boards were quite large.

The easiest attempt would be the CPU from the 35-80 into the 35-135 as you will get the aperture range perfectly covered. If memory serves --not guaranteed thee days -- the 35-135 should have sufficient room inside. I'll rummage through my cupboard and find my sample of the 35-135 later to check on this.

Erik Lund

  • Global Moderator
  • **
  • Posts: 6513
  • Copenhagen
    • ErikLund.com
Re: alternative option for CPU
« Reply #2 on: September 19, 2023, 08:26:48 »
Yes i concur. 
The 28mm f/3.5 is a nice lens but there is not much room for the print board unfortunately,,,
Erik Lund

Bern

  • NG Member
  • *
  • Posts: 89
  • You ARE NikonGear
Re: alternative option for CPU
« Reply #3 on: September 19, 2023, 09:55:30 »
Glad to know that this might be a viable approach to chipping my Nikkor.

I will try to utilize the cpu from 35-80mm first for the 35-135mm.

Will also try to find other donor lenses for this project.

Keep shooting,
Bern