Orthoplan repair

[j_cl]

Hello, please pardon my English. I recently purchased the base and drive stage of a Leitz Orthoplan microscope. The mechanics are in excellent condition, the lubricant is still the right consistency, but the stage will not move up and down. I am hoping that someone here is familiar with the inner workings of the stage drive and can give me some clues.

The first problem is that the output gear of the mechanism turns freely by hand even when fully assembled. The coarse and fine adjustment knobs are both able to move the output gear, but because the gear is so loose, it cannot overcome the static load of the stage to move it. I suspect the issue is a bad connection between the double crown gear that meshes with the fine adjust and the plastic worm that meshes with the coarse adjust, but that is just a guess.

The second problem is this piece of brass in the sliding part of the drive assembly. Hopefully you can see it in the attached picture. To me, it looks out of place and it seems to block a large range of the travel of the drive. Is it supposed to be there? There are signs of modification to other regions of the Orthoplan but the brass is such an odd feature that I cannot tell if it is original.

Thank you!

[Diana1982]

Hi!

I´m very familiar with this Orthoplan drive unit and what I can say for sure is, that this brass piece has to be put out. It is not original. There is a pin, which has to run freely in the slot, where brass piece is.
But maybe someone else took that pin away?! The pin, I´m writing about, is just for the end stop mechanism (some parts of that mechanism are shown on your picture (about 10 o´clock) - a brass "U" with two forks.

Kind regards
Diana (who maintained lot of those drives)

[Diana1982]

If the fine coarse knobs and coarse drive knobs all move the output gear and you can´t find any broken mechanics like broken teeth and so on, everything should be ok so far. Maybe, bad contacts would cause some play or the opposite later, when you are working on the microscope, but this should be not the reason, why the stage can´t move up and down.

Remove the brass piece, you showed us, and see further then.

Diana

[Diana1982]

Or the whole system is such damaged by blocking of this ominous brass part, that something inside the drive is tored off, and runs as long, as there is no load on it.

Perhaps it would be clearer, if you´d made a youtube video of your loose running output gear...that sounds a bit strange and that is not ok, if nothing is broken...

[Diana1982]

Here a picture with the pin, I mean:

The picture is part of an other thread, where I maintained a Orthoplan drive.

Perhaps you find further useful pictures there:
https://www.mikroskopie-forum.de/index.php?topic=36862.45

[j_cl]

Thank you very much, Diana!

The pin mechanism is still there but the pin is completely bent. Your theory that someone tried very hard to move the platform without knowing the brass piece was blocking motion sounds likely. When I have a chance after the end of my work week I will try to remove the brass, repair the pin, and see if the worm drive is damaged or stripped internally. If I cannot find a solution I will take your suggestion of coming back to this post with a youtube video.

[Diana1982]

Hello unknown writer (a name would be nice    ),

Here is another thread on the topic of Orthoplan drive and it´s Achilis heel (hope this expression is also right in English):

https://www.mikroskopie-forum.de/index.php?topic=37228.0

You will find an attached GIF there, which could show the same effect, that you have...
Unfortunately the person, who excellently built two spare parts for the Orthoplan drive, has deleted his postings.

Regards
Diana

[j_cl]

I'm Jack, I'm from the United States. This forum has to be the first website I have used in my time on the internet where a four-character username was actually available so I jumped at the chance to take it.

I was able to remove the piece of brass by soaking it in penetrating oil and poking it out from behind. I still struggle to imagine what the the users of this Orthoplan must have been looking at to have wanted such a limited focusing range.

I further disassembled the gear mechanism and thankfully found that no teeth are chipped off or rounded over. I think the issue is the connection between the plastic worm gear and the brass piece that mates to it. (both centered in the frame of my picture). I assume that the brass gear is supposed stay rotationally locked to the worm gear, but it is able to slip freely if any resistance is applied. Although, there is grease in that hole, so maybe it is supposed to spin. After tearing this mechanism down to its elements this loosely coupled press-fit gear is the only unusual thing that I've seen.

If that gear should be tight instead of loose, I can glue or epoxy it back into place. Does that sound right to you, Diana?

[Diana1982]

Dear Jack,
The two parts, you show, should be ONE piece as you can see in my picture below...
Never saw this error, like you show it before...

Regards Diana