Internal and Door O Ring Replacement for Nikonos IV-A

For a long time I skipped the Nikonos IV-A whenever one was offered to me, because I had it marked as unserviceable due to its non standard film door o ring.

Then I realised, that a standard o ring probably could be a proper replacement for a worn out original seal.

So I ordered a cheap non working Nik IV to try out, if I could get it sealed with the right o ring. After some trial and error I finally found a size that does seal it.

By playing around with it, I realised that the Nikonos IV has some advantages over the Nikonos V, which make it difficult for me, to choose, which I should prefer as an underwater camera. One advantage is the much easier to determine exposure indicator. The single LED of the Nikonos IV-A, which either shines continuously if the exposure is right or blinks, if it is not optimal, is much easier to spot if you are wearing a dive mask, than the delicate numbers of the Nikonos V.

One thing to mention, about the door’s o ring is the fact, that it in the beginning was a litte bit to tight and kept the pin on the door from protruding deep enough on the push button which engages the camera’s frame counter.

What I did, was that I pushed on the back of the door, near the pin’s position for some time, until the o ring got worked in and the frame counter worked flawlessly.

Another idea would be, to try to purchase a somewhat softer o ring, but I was not able to source one softer than NBR70. Maybe with an NBR50 the dimension could even be a bit thicker than the 3 mm I used, making it an even safer seal.

So, what I finally did, was getting myself a second Nikonos IV in subpar state and building one working and nice looking camera out of the two.

During this process, of course I replaced the internal o rings, a process pretty similar to how to do it with the Nikonos V.

The dimensions of the o rings can be taken from the Nikonos IV-A O Ring Cheat-Sheet that can be downloaded as a pdf either.

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