Zeiss phase cpndenser iris adjustment stiff

[MikeBradley]

The bright field aperture adjustment on my Zeiss Standard phase condenser is extremely stiff, more so at the open end position of its travel than the closed position. I have tried loosening it by repeated back/forth movement and while this helped initially it wasn't sufficient. I found posts and links on this forum explaining how to free up and lubricate the phase ring and I expect that similar advice exists for the aperture adjustment but I haven't been able to find them yet. Can anyone suggest a link? Thanks

Michael

[Hobbyst46]

There were posts about maintenance of such condenser, even one by myself I think, but cannot find them.
Anyway, it is very likely that the leaves of the aperture are frozen due to dried grease or oil. They should be clean and absolutely dry.

Zeiss Phase contrast condenser catalogue number 465277:
One way to solve the problem without complete disassembly is to remove the central black slot screw, which holds the circular top face plate in place. Also, remove the front lens (marked "1.4 achromat aplanat"). So you see and can touch the aperture leaves. Have some petrol ether ("white benzin", "ligroin") ready. Folks here often recommend lighter fluid as well. Close the aperture as far as it goes, without overdue pressure. Place one drop of liquid on the leaves and let it spread (do not use a Q-tip, which might leave fibers between leaves). After a few seconds, open the aperture. Re-close, wipe the dirty liquid with a lens tissue or KimWipe. Repeat this process many times; try to do it on both sides - top and bottom - of the aperture. The final result must be a clean dry leaf assembly.
It worked for me, more than once !

P.S. this way, I have managed to free and clean other aperture diaphragms as well: the Zeiss field aperture, for example.

[MicroBob]

I have used this method (usually with success) on lots of old camera apertures and leaf shutters. The contaminating grease or oil usually came from the circumference were grease on the blade actuator or other mechanics leaked in. This explains why the procedure has to be repeated often - one has to get the grease away from the outer border too.
A word of warning: Some phase discs are just paint on glass and are damaged easily.

Bob

[MikeBradley]

Doron and Bob, thanks for the tip. I tried it with Camping fuel (Naphtha) and it solved the problem immediately. Thanks.
Michael

[MikeBradley]

Buoyed by the success with freeing the phase condenser I decided to try freeing the aperture on a Zeiss DIC/Phase/BF. But on this unit the iris leaves are fully open and any adjustment is impossible. It is almost as though the aperture was locked in the open, could this be the case? If so how can it be freed? Thanks
Michael

[MicroBob]

Hi Michael,
it often helps to heat to 60°C for an hour or two. Then the blades might loosen up enough to move them. Usually the blade edges are still accessible when the aperture is fully opened. This allows the application of the solvents Doron mentioned above. Don't use force. Usually it is possible to dismantle the whole aperture but I would only do this if nothing else works. It is quite fiddly to reasemble it.

Bob

[Hobbyst46]

Buoyed by the success with freeing the phase condenser I decided to try freeing the aperture on a Zeiss DIC/Phase/BF. But on this unit the iris leaves are fully open and any adjustment is impossible. It is almost as though the aperture was locked in the open, could this be the case? If so how can it be freed? Thanks
Michael

The "Zeiss DIC/Phase/BF" - is it a turret condenser with several aperture diaphragms ? one for each position ?
Irises are useful and effective when partially closed, not when locked fully open.

[MikeBradley]

Doron, I was going to reply by saying that it only had the BF iris as I've only ever used phase condensers where there is only one and none were visible on other windows, but your question prompted me to look more closely at the DIC windows. Initially I could see no sign of irises there either but after application of heat to the BF aperture it opened and irises "flowered" in all the DIC windows. It seems as if the condenser had been stored with the irises FULLY open and it took the careful application of heat to loosen things up. Since the heat and naphtha had been applied only to the BF aperture it's likely that this had been the problem all along. The condenser seems to be fully functional now, all I need now is the remainder of the DIC kit.
Thanks
Michael