Cleaning an Agfa Karat focus helicoid
I couple of days ago I cleaned up the frame advance mechanism on my Agfa Karat 35mm viewfinder camera, but the one remaining area which still needed attention was the focus mechanism. When I received the camera the front element was seized almost completely solid and I couldn’t turn the lens, so in order to get a working camera, that was the next thing I needed to fix.
These pictures can also be viewed full size here.
I did some Internet research and found that a hair dryer applied to the front element of the lens can get the old grease loose enough to at least enable the focus to move. The idea outlined was to get the focus set to infinity and then apply lighter fuel on cotton buds to the back of the lens and wipe/wash the old grease out.
My first attempt was to follow exactly this approach and see if I could get the focus working. After the application of some heat I could get the focus to move with a lot of effort and then with a drop of lighter fluid applied the back of the lens I tried working the focus to loosen the grease. After about 10 drops of fluid and 10 turns of the focus, I could see that this approach was starting to work, but I was concerned as to where the old grease was going to go. I could see some grease oozing out of the front of the lens and I could mop some of that up with cotton buds, but after a while I decided I would be better trying to remove the front element and properly clean the grease out.
So, I opened the film chamber and with a lens spanner I removed the back lens element and then the ring which holds the shutter onto the front standard. As it happens, once I examined the shutter in more detail, I found I didn’t need to actually remove the shutter from the camera – all I needed to do was remove the focus scale trim by unscrewing the three grub screws and lift it off. I could then unscrew the front lens element completely out of the shutter and clean it up properly. However, I wanted to make sure that the lighter fluid and old grease hadn’t contaminated the bellows or front fitting and with the shutter removed it gave me the opportunity to clean up the front cover and blow the dust out of the front mechanism.
Once the focus mechanism was free of the shutter unit cleaning it was quite simple using lots of lighter fuel and cotton buds to wipe both parts of the mechanism clean. As a word of warning here be careful not to let the cotton buds touch the shutter blades as you are cleaning up the shutter part of the screw thread – you don’t want to transfer the dirt to the shutter.
Once the threads were clean I applied a touch of lithium based fresh grease to the lens part and screwed it back into the shutter, winding it in and out a few times to distribute the grease.
Just before I put the shutter back on the camera I dealt with another issue which I hadn’t really seen before I got the lens out to examine. Both the front and back elements had quite a bit of fungus growing on their surface and the front element was hazy. I successfully removed that with a bit of vinegar applied with a cotton bud and wiped off with a lens cloth.
The hardest part of the reassembly was refitting the ring on the back on the shutter which holds the bellows in place. It was easy enough to get the parts aligned, but I couldn’t get the treads to engage. I tried several times with the front standard collapsed into the camera body without success but finally found that I could successfully re-engage them with the front popped out and my fingers pushed into the back of the camera. I wonder if the fact that the bellows were fully stretched kept some material from getting in the way?
Anyway, with the ring finally fitted and the back element refitted onto the back of the shutter I positioned the focus ring by setting the camera on a tripod and using the T lever to lock the shutter open. With the aperture set to it’s fastest setting of f/3.5, I could then use an old focusing screen from an SLR held over the film position in the camera, and using a 5x eyeglass I could focus the camera on infinity and then refit and lock the focusing scale.
So the Karat is now fully working – I just need to find a couple of Rapid film holders …..