Fixing the Carl Zeiss 50mm 1.4

Suddenly the CPU stopped working. My Nikon D7000 would not recognize the ZF.2 Carl Zeiss 50mm f1.4. It was obvious that the CPU had died a sudden death and the lens had turned from ZF.2 to ZF in a split second. Even worse, the locking of the aperture ring makes it more difficult to operate as an Ai-S lens. So I had to do something.

First thing was that I tried to trick Zeiss to send me a replacement CPU. They replied they do not supply spare parts to individuals and I should go to the local service representative. This happened to be Light&Byte who asked me for the incredible amount of CHF 100.- (~$100) to tell me what the problem is. This would also be a down payment in case I wanted a repair. I found this amount of money exorbitant, especially for a problem that is so obvious and for which the repair would cost much less than $100… I am sure fellows in the UK enjoy a much better service from Carl Zeiss…

So there was only one solution. The notorious Dandelion chip. I buy all my CPUs from this seller and so far I am pretty happy. The Dandelion works well in general. I have seen some variation in the programming activation sequence, sometimes it is 1-5-1 or 1-6-1 and another problem I had was related to its strength: the casing is relatively soft so any misalignment during installation will destroy the chip.

However, the CZ case is pretty simple: all that is needed is to replace the CZ CPU. This can be done in a way that the lens is still serviceable. What I mean is that the CZ CPU is easily removable. Just unscrew the small screw that keeps it in place and gently pull out the whole electronic construct (it has a soft, bending board barely inserted into the connection holder). I actually unscrewed the whole plastic prong and tried to see whether the soft board had moved and this caused any loss of contact. Apparently it was dead-dead…


The Dandelion chip can be glued in the place of the CZ CPU. With a fine file remove the CPU and make enough room for the Dandelion. Then add glue only on the plastic removable part and align the Dandelion as you would otherwise. This way, if ever needed, you can remove the plastic holder with the dandelion and replace it with the original CZ part.


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