Dallmeyer 3A disassembly

[case-ie]

Hello everyone,

Sorry it became such a long story

The soft focus tube on my Dallmeyer 3A was frozen. Read a earlier thread on this, and stuck soft focus seems to be quite common and difficult to repair. I tried it anyhow and was lucky, Front and back came off easily. The soft focus tube did not, I heated the tube au bain marie –so cooking water, a plate on top, a piece of cloth on that and then the lens–, I heat the lens very slowly this way and after 1/2 an hour I was able to unscrew the soft focus tube, after another 1/2 an hour I could also unscrew the middle lens in it's own part of tubing,
but did not succeed to get it out of that part of tubing, must be possible but not necessary, I can reach everything now.

For clarity and people who want to do this there are in fact 3 parts of tube.

-The main Barrel
-the soft focus tube.
-and the tube with the middle lens. don't forget to take out the little screw before you try this

I will try to attach some pictures.

And then I have two questions;

The diaphragm seems to be turned in the barrel, when it is open the little handle stands between stops 8 and 11 so you can stop it down maybe one time . I took out the little screw but did not manage to turn the hole diaphragm to the right position how can I dislodge it without damage?
The black paint, if it is black paint, on the inside of the lens comes of very easily, apart from being careful how can I cover this again?

Thanks
Kees.

By the way I don't think I ever saw such nice pieces of glass before.

pict 1, main barrel and from top left, soft focus tube, back lens, middle lens in it's tube and front lens
pict 2 middle lens in its tube
pict 3 diaphragm in barrel.

[Steven Tribe]

First of all - I have asked the Mods to move this to the DIY section!

Before saying anything, I would like to see some more photos of the side and the serial number!

Boiling water and these lenses are not a good combination! I have had devirification on the front achromat of a 3A at much lower temperatures than 100 deg C!

[QUOTE]I took out the little screw but did not manage to turn the hole diaphragm to the right position how can I dislodge it without damage?[/QUOTE]

The iris ring is a pressure fit - just held by the screw(s). It is often difficult to budge because of metal oxidation and build up of blackening material at the edges.

[case-ie]

Thank you for your reply. I would say lets move it.
I could have been more clear about it but off course you have to remove cemented parts before applying any heat.
The serial number of this lens is 82166.

[Steven Tribe]

As I can see 4 sections making up the cell assembly (1 for the front and 3 for the rear?) and a plain barrel (no sleeve), I can only assume this is one of the "front turn models", where the internal rear glass and the front achromat move away from the rear lens. There are a number of versions of this type - so side views would be helpful.

[case-ie]

Yes Steven you are right. Everything moves away from the back lens. Tried to move the whole diaphragm but did not want to use to much force, I don't know enough for that. So closed he lens today. Maybe later another try.
Not much corrosion in this lens though, it looks freshly painted. There are also a lens board and flange.
Here is a side view and a picture of the diaphragm.

[Steven Tribe]

I havn't done any work on the later iris fitted/front turn Dallmeyer soft lenses!

But is pretty obvious that if you remove the central barrels screws, unscrew the iris lever, apply penetrating fluid to both circular lips, then the whole unit can be withdrawn through the front or rear. I think it is a better idea to remove and service, rather than attempt to turn the unit with some makeshift tool. You may find that the retaining screw have been sheared off in the iris and must be replaced with oversized (metric?) screws. It is probably the paint which is holding unit in the barrel! You will have to refinish the mat black. You will also have to be prepared to dismantle (if it doesn't separate during removal) the iris leaves and reassemble afterwards!

My suggestion for getting the iris out is either:

- using a metal tube or round wood section which fits exactly into the circular 90 degree bend at the edge. OR

- make a smaller sector piece (45 degrees?) which fits in this 90 degree bend. "Attack" the next section when the first slight movement(1mm?) is detected.

Don't change your mind halfway through the operation and try to release in the other direction.

I think it would be best to wait for others to comment before proceding!

[case-ie]

into the circular 90 degree bend at the edge. OR - make a smaller sector piece

Do you mean something that fits the main barrel exactly or at least part of it and with that try to dislodge the outer stationary ring. I tried that with a little piece of wood. But thought it needed to much force. The inner turning ring would move a little (when stopped down a bit) and spring back in position, but I think when I push that out I dismantle or even ruin the whole diaphragm.
Anyway by taking out the whole thing, I would have to repaint and I'm not ready for that yet. Maybe the person who assembled it wanted to prevent this lens to be used stopped down