Koni Omega film back pressure plate not withdrawing

alfu · Apr 15, 2015

Hi guys, I have a Rapid M with a 120 back. I know that these backs are meant to be ingenious and retract the pressure plate as the film is being advanced. My problem is that this does not seem to be happening and my film is getting scratched on the film gate, + the pull to advance the film is stiff.

When I have the back off the camera I can always push down a bit on the plate, against the spring. However, there is no give throughout the advance motion when it is mounted on the camera body.

Does anyone know what the problem could be or what I should do to fix it? I had a look at the service instructions, http://www.mflenses.com/koni-omega-back-repair.html, but it doesn't seem to pertain to the pressure plate?

alfu · Apr 16, 2015

Frame spacing is fine, except for two frames where it was around 1mm.

alfu · Apr 16, 2015

Cool, thanks! Do I then follow the instructions I linked? How does the pressure plate system work?

alfu · Apr 16, 2015

Thanks again. I'll buy another back first before working on this one. Unfortunately I don't think there are any repairers in Australia.

alfu · Apr 16, 2015

Haha. Very true. But right now I've discovered if I tape the film gate I can stop the scratches. And as long as the stiff film advance does not break anything, I can keep using the camera.

If I break the back I won't be able to use the camera anymore!

alfu · Apr 16, 2015

I got the idea from this thread: https://www.flickr.com/groups/65927769@N00/discuss/72157629614537858/

I locked the film back in with no film. I took the lens and dark slide off my camera. I pulled the film advance lever out while touching the pressure plate. If it retracts, I expect to have some give between locking the lever in and pulling it out?

Then I tried the same thing with the film. I can see that while advancing film the film is rubbing against the camera body.

alfu · Apr 16, 2015

Thanks heaps!

wilper · Apr 16, 2015

Speaking of such backs. I have a Rapid Omega that I don't use because the spacing in wonky. Is there anyone (preferably in Europe) that can service backs or sells serviced backs?

alfu · Apr 16, 2015

Ok. I've worked out what the "pressure plate" mechanism is. So I originally thought that the pressure plate was the black thing that pressed against the film. In part, this is correct. You see that this plate is mounted using two screws, on springs. If you take the screws out (be careful not to lose the washers), you will remove the plate and you can see that the plates sits on a metal tab. This tab is "released" when the film is advanced. When the lever is returned to the original position, this tab is locked in the up position so that the plate cannot move once it is on the camera.

I noticed that my plate was not moving at all before. But now that I have taken and replaced the screws, the plate can move quite a bit before mounting on the camera. After mounting, it is held in place, until the film advance moves, where there is a bit of give.

I suspect that my plate was incorrectly mounted on the screws?

Koni Omega film back pressure plate not withdrawing

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