How to fix focusing ring of Revuenon 1.4/55?

alex ph · Joined: 16 Mar 2013 Posts: 1571

I've got an Auto-Revuenon 1.4/55 with clean optics but with a loosy focusing ring. So when I focus in both directions the ring spontaneously "slips" from time to time. When I squeeze stronger the ring it does not "slip" and I have the full focusing move.

It seems to me an easy fix: must be a lacking screw somewhere in the barrel? Correct me if I am wrong. But I don't see how the focusing ring is connected to the barrel. Maybe there are some screws under the rubber on the focusing ring? Is it necessary to strip it off to fix the problem?

The lens version I have looks precisely like this one.

I tried to have some info online but haven't find any clear instruction regarding this precise issue.

Any help would be really appreciated.

55 · Expire: 2022-06-15

Alex,

I believe my Auto Sears 55mm is the same lens as the Chinon in your link. If your lens is the same as mine, I think you can fix your focus ring with just a small, flat blade screwdriver. And you shouldn't need to remove the focus grip.

First, focus the lens to its minimum focus distance. Above the focus ring you should now see three screws around the barrel.

#1

Loosen each screw three or four turns - they don't need to be removed. Then the top of the barrel / filter ring piece should unscrew and lift off from the lower barrel.
Now you should be able to see four screws.

#2

These screws fasten the focus ring to the focus helicoid, and I'm guessing the screws on your lens are loose.
Infinity focus can also be adjusted when these screws are loose, so be careful to turn the focus ring all the way to MFD before you tighten them (there should be a hard stop there).

I've read some people apply clear nail polish to screw heads to help keep them in place after tightening. And potential nail polish or glue are the reasons why I often apply solvent and heat to screws before I try to loosen them. That helps to minimize the chance of stripping screw heads.

Tim

alex ph · Joined: 16 Mar 2013 Posts: 1571

Thank you very much, Tim! That worked like a charm. I tightened the four screws that you indicated, and the focusing ring goes now without any "slipping".

But when I was unscrewing the screws I accidentally moved the lens, and it went off the diaphragm pin. After the initial 3 minutes I spent another hour trying to put the lens back aligned to the pin. This is not an easy task, as the helical screw is composed of two parts, including a copper inlay ring. When you screw it into the helical cage, the lens unscrews, and vice versa. Nothing worked.

After many void attempts I left it over. So I reassembled the lens with the aperture fixed at around f2, just to keep the dust away from it. And suddenly the pin took a right position, I did not understand how. Now the diaphragm works as intended or almost, the focusing ring does not slip. But... I lost infinity. That makes me lough, with this lens I did not have an easy solution. So, I will disassemble it back again and will try to fix infinity.

By the way, the lens block is very well built and gives an idea of a tightly encapsulated construction. The diaphragm control is well hidden inside, and you will hardly take the lens a part by accident.

55 · Expire: 2022-06-15

You're welcome, Alex. I hope you'll be able to get everything working again.

It's fascinating - and frustrating - to see the variety in lens constructions. Some are easy to work on, but others...

alex ph · Joined: 16 Mar 2013 Posts: 1571

Thank you, Tim. After another hour of tries and give ups I realized that I am pretty flexible with the "slipping" focusing ring and may fix it after I get infinity with the lens. So I first adjusted the helical position of the lens inside the barrel, so that it reached infinity. And after I fixed the screws of the focusing ring positioned at infinity mark. It works now as it should.