Hello all,
The issue of a partially frozen field aperture diaphragm on Zeiss Standard microscope has been mentioned on several occasions. One way to solve the problem is complete disassembly and cleaning of each and every leaf of the diaphragm. However, re-assembly is tedious and time consuming.
I have recently succeeded an easier and faster approach. A non-working old GFL scope (waiting for me to re-furbish it) that I recieved with my working scope. Nearly stuck field diaphragm. So I removed the diahpragm unit from the base plate. Removed the top cover glass plate, in order to gain access to both sides of the leaves.
Closed the aperture, then flooded the leaves with several drops of petrol(*) from a pipet. Opened and closed several times. Wiped the leaves with lens tissue moistened with petrol. Repeated the process 3-4 times. In between, flooded the inner perimeter of the wide open diaphragm, to cause some liquid to penetrate from the side. Wiped the leaves again.
The diaphragm can now be rotated very easily, very smoothly. Leave it aside for a day, so the liquid evaporates away. The problem is solved, at least for a couple of years (based on previous experience).
Hope this will be of help to someone.
(*) Petrol = octane, gasoline, ligroin, a light car fuel. Possibly a cigarette lighter fuel. Not alcohols, acetone, ether, xylene, toluene.
Simple cleaning of a partially frozen field diaphragm
Simple cleaning of a partially frozen field diaphragm
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Re: Simple cleaning of a partially frozen field diaphragm
Graphite also works well for that. Sprinkle some on the blades and work it in. Then blow away the excess. I have done this on camera lenses, just don't get it on any on the glass lens. They usually sell it in the lock and key section of hardware stores. It's often used to lubricate locks.
On camera lenses some diaphragms can have a coating on them that a solvent will remove.
On camera lenses some diaphragms can have a coating on them that a solvent will remove.
Re: Simple cleaning of a partially frozen field diaphragm
Hi Doron,
I have a camera repair handbook that shows general techniques and special methods for camera of the 1970s and 80s, written by camera repairman Tomosy. The process you describe here is one of his standard methods to get a stuck aperture or leaf shutter going. After cleaning he applies lighter fluid with some very fine graphite, moves the mechnism and blows out grphite that hasn't attatched to a surface. I have repaired lots of cameras and lenses this way and only rarely had to dismantle more. One thing that has worked well for me was to drop lighter fluid in, move mechanism, remove greasy lighter fluid with a finger tip an tissue, repeat several times. With cameras the main problem is grease from the focussing helix that moves towards the aperture blades.
The graphite is there to lubricate blades theat are moved frequently and quickly- I would leave it out for microscope applications
Bob
I have a camera repair handbook that shows general techniques and special methods for camera of the 1970s and 80s, written by camera repairman Tomosy. The process you describe here is one of his standard methods to get a stuck aperture or leaf shutter going. After cleaning he applies lighter fluid with some very fine graphite, moves the mechnism and blows out grphite that hasn't attatched to a surface. I have repaired lots of cameras and lenses this way and only rarely had to dismantle more. One thing that has worked well for me was to drop lighter fluid in, move mechanism, remove greasy lighter fluid with a finger tip an tissue, repeat several times. With cameras the main problem is grease from the focussing helix that moves towards the aperture blades.
The graphite is there to lubricate blades theat are moved frequently and quickly- I would leave it out for microscope applications
Bob
Re: Simple cleaning of a partially frozen field diaphragm
@Bryan
@Bob
Yes, graphite is a solid lubricant, have used it to lubricate door keys. Scraped black lead pencils (2B or 3B pencils if that rings a bell...
) to get powderous graphite. However, in the specific case of the field aperture diaphragm, I am not sure that it is suitable. The field aperture diaphragm is positioned directly above a first surface, 45 degrees mirror. In fact, they are part of the same unit. That mirror directs the illumination beam from the light source upwards, through the field aperture, into the condenser. Some graphite powder might later fall from the aperture onto the mirror... Although the amount of graphite for the job is really very small.
Bob, thanks for the info about camera shutters and lenses - such repairs are way beyond my capability
...
@Bob
Yes, graphite is a solid lubricant, have used it to lubricate door keys. Scraped black lead pencils (2B or 3B pencils if that rings a bell...
) to get powderous graphite. However, in the specific case of the field aperture diaphragm, I am not sure that it is suitable. The field aperture diaphragm is positioned directly above a first surface, 45 degrees mirror. In fact, they are part of the same unit. That mirror directs the illumination beam from the light source upwards, through the field aperture, into the condenser. Some graphite powder might later fall from the aperture onto the mirror... Although the amount of graphite for the job is really very small.Bob, thanks for the info about camera shutters and lenses - such repairs are way beyond my capability
...Re: Simple cleaning of a partially frozen field diaphragm
In a camera lens the problem is there too but in practice it is less likely to show because the camera lens is used in the horizontal plane most of the time. With an analog camera you even had a new image sensor for every shot.Hobbyst46 wrote:The field aperture diaphragm is positioned directly above a first surface, 45 degrees mirror.