Repairing Agfa Parat-I: turning focus ring doesn't turn lens.

[Laurens]

Hi,

I have a problem with my Agfa Parat-1 half frame camera. It doesn't focus correctly, and that's because the lens doesn't rotate when you turn the focusing ring. I've removed the focusingring-lens assembly from the camera. I've found out the lens and the focus ring can rotate independently of one another.
Behind the part that says ''1:2.8/30 agfa apotar color", there should be 3 screws holding the whole thing together. I can see those screws from the back of the assembly. Does anyone know how i get to those screws, or how to remove that part without scratching/bending it?

I can make pictures if necessary.

 

[Mike Wilde]

Usually the focus ring attaches to the front of the tessar (in your case a colour corrected apochromatic type) lens by use of three quite tiny brass type screws that enter the outside edge of the focus ring, and normally bite into the bottom of a groove in the front of the lens housing barrel.

I would gingerly try to back off the fasteners that you found that allows the focus ring to move independent of the lens, until the focus ring can be pulled off of the front.
If the fasteners come out there are two problems - one is that are small and a bitch to find once dropped; work over a smooth towel on a work bench. The second is that getting the thread to start again is tricky.

I suspect the helical that the lens front rides forward and back in has the dreaded 'green grease syndrome' that old Agfas are famous for.
With age it turns to a rock hard substance.

I combatted this on an old ansco/agfa folder with a seized Tessar by drizzing with lighter fluid applied with the end of a tooth pick, drop by drop over the course of a few days.
Then I was able to grip the lens barel with a pair of pliers and gently twist it free of its stuck moorings.

Try to figure what the orientation is when it is fully bottomed; mark the lens barrel and camera body with match marks.
Then you have a 33% chamce of gettign it right if there are three tracks on the helical when it comes time to put it together again, and might be able to avoid needing to recollimate
Collimation is a fancy word for the lens to be focussed at infinity on the film plane when the lens barrel marker says it is focussed at infinity.

Scrape off all grease you find, and then try the smallest dab of molly slip, or graphite. Rethread the helical and recollimate the lens to infinity by taping a temporary focus screen into the back and firing the shutter; jamming the escapement if the shutter has no bulb setting is sometimes required; good luck.

I also freed the green grease for a stuck rangefinder by leaving it in a warm oven after a roast was finished cooking. I pulled it out after doing the dinner dishes, and by then the greese had softened enough to moved a bit; enough to drip in lighter fluid with a toothpick to the bound up thread, and work it back and forth until more solvent could be worked in.

Good luck with your restoration.