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PostPosted: Sun Apr 14, 2019 6:13 pm 
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I am trying to refurbish and bring life to a very old Zeiss GFL stand, that was so far stored in a remote cupboard. There are two issues with it. One, regarding the field aperture assembly, will be described in a future post. The other challenge is the fine focus mechanism. The fine focus control functions but is too stiff and requires much more force than the normal. The coarse focus is fine. I suspect that the problem is due to old hardened grease.
Some time ago, a kind forum member has uploaded a link to a draft of a concise record, including sketches, written by his father, of disassembly and repair of the fine focus mechanism. I apologize for having forgotten the name of the poster - hopefully he will read this post and reappear! I followed the first steps as described, dismantled and separated the focus mechanism from the microscope arm, as shown below. Identifications and notations of parts are cited from the above record as far as I understand them.

The focusing gear moves the thin push-rod that in turn pushes the block against a stopper spring (photo(1), marked "Spring", and photo(3), left side of the block). The gear is actually hidden from sight by the block. The red circles symbolize invisible rollers that are caged within Vee-shaped grooves. The end of the push-rod itself is connected with a thin wire spring (photo (3), right side of the block, hardly visible). In the end face near that end of the push-rod, there is a retaining ring (photo (4)). It is locked with a side screw (not directly visible). That end face is touching the base plate of the whole assembled microscope. The face opposite the block is the female dovetail of the coarse focus, not related to the problem.

Complete disassembly of the mechanism appeared tricky. The heads of six screws are "locked" with red Loctite, against tinkering by amateurs (me). I tried to go around it. Yet, drops of light machine oil into the ends of the Vee-shaped grooves, from the outside, made no difference. Removal of the end plate, cleaning and re-greasing the stopper spring (photo(3))did not help. Tinkering with the two bolts was futile - hopefully it did not worsen the situation. I did not try WD-40, nor heat: this gizmo is a combination of brass and steel parts, and each has its own expansion coefficients.

Further dismantling might require a custom pin-spanner to remove the retaining ring without deburring. But I am not sure that it will expose the problematic hard grease area.
So, what would you suggest to do next? thanks in advance for ideas! perhaps links to available maintenance manuals?


Attachments:
fine focus mechanism (1).jpg
fine focus mechanism (1).jpg [ 115.22 KiB | Viewed 235 times ]
fine focus mechanism (2).jpg
fine focus mechanism (2).jpg [ 172.3 KiB | Viewed 235 times ]
fine focus mechanism (3).jpg
fine focus mechanism (3).jpg [ 173.71 KiB | Viewed 235 times ]
fine focus mechanism (4) .jpg
fine focus mechanism (4) .jpg [ 112.69 KiB | Viewed 235 times ]

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PostPosted: Sun Apr 14, 2019 6:56 pm 
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My apologies if you know this, but in both the GFL and WL fine focus is tightened and loosened by turning the fine focus knobs against or away from each other.


Attachments:
fine-focus-GFL.jpg
fine-focus-GFL.jpg [ 94.2 KiB | Viewed 217 times ]

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PostPosted: Sun Apr 14, 2019 7:35 pm 
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75RR wrote:
My apologies if you know this, but in both the GFL and WL fine focus is tightened and loosened by turning the fine focus knobs against or away from each other.


Are you sure about this? It is been a while since I had one of these apart but I think to remember a fine focus shaft that runs from one knob to the other. I might be wrong though.

@Doron: I think I have made a special tool for this job. I have a look tomorrow, I might even have a Zeiss Winkel GFL in the right state of disassembly and can maybe give a hint how to get into it. As far as I remember it was straightforward to disassemble apart from the one special tool.
To loosen screws it is good to apply some fine oil and then put the screwdriver in the slot and apply some knocks with a small hammer. This loosens whatever is in the thread and allows the oil to penetrate much better. The screwdriver should fit the slot in thickness and lenght and be ground well.

When reapplying lubricants it has to be taken into account that there is much surface in contact and grease at the wrong points gives too much damping for the fine focus. I would suggest to grease the ways and oil the shaft.

Bob


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PostPosted: Sun Apr 14, 2019 9:41 pm 
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75RR wrote:
My apologies if you know this, but in both the GFL and WL fine focus is tightened and loosened by turning the fine focus knobs against or away from each other.
MicroBob wrote:
Are you sure about this? It is been a while since I had one of these apart but I think to remember a fine focus shaft that runs from one knob to the other. I might be wrong though.

Thanks 75RR and Bob,
Funny ! as occasionally mentioned on this forum, not all Zeiss Standard microscopes of the same model are entirely identical to each other!
I own two GFL scopes. One is in use, the other, which I believe is somewhat older, is under reconstruction. On both of them, the coarse focusing behaves exactly as described in the manuals: a special single control knob, coaxial with the coarse focusing knob, and fitted between the focusing knob and the arm, controls the tension of the coarse focusing movement.

The fine focus knobs are NOT the same. On the scope in use, the rightside and leftside knobs can be rotated in mutually opposing directions (from the operator's point of view). Such manipulation seems to affect the tension, yet since the fine focus works nicely I will not test it too much. Also, the knobs are uniformly knurled, no small screws on them.
In the scope under reconstruction, the one that bothers me, I cannot rotate them in opposing directions (I will not attempt with tools, though). Each knob has a small set screw that apparently locks it to the shaft. Whether this screw and its function are related to the tension of the focusing movement - I doubt but cannot say.
Bob, thanks for the tips. When I figure out what to do they will certainly help!

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PostPosted: Mon Apr 15, 2019 5:37 am 
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Quote:
In the scope under reconstruction, the one that bothers me, I cannot rotate them in opposing directions (I will not attempt with tools, though). Each knob has a small set screw that apparently locks it to the shaft.
If it is fixed, firm measured finger pressure will not break it. If it is not fixed then it might do the trick.

As it is a little too tight, you want to turn the fine focus knobs away from each other. As you face the front of the microscope turn the right one towards you - turn left one away.

Just a few mm will do.


Attachments:
fine focus knob-.jpg
fine focus knob-.jpg [ 148.82 KiB | Viewed 165 times ]

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Last edited by 75RR on Mon Apr 15, 2019 7:42 am, edited 1 time in total.
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PostPosted: Mon Apr 15, 2019 7:32 am 
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75RR wrote:
Quote:
In the scope under reconstruction, the one that bothers me, I cannot rotate them in opposing directions (I will not attempt with tools, though). Each knob has a small set screw that apparently locks it to the shaft.
If it is fixed, firm measured finger pressure will not break it. If it is not fixed then it might do the trick.

As it is a little too tight, you want to turn the fine focus knobs away from each other. As you face the front of the microscope turn the right one towards you - turn left one away.

Just a few mm will do.
I think that it makes sense, that thd user can simply adjust thd friction on the fine focus movement. Unforetunately, in this specific case, turning the knobs against each other is impossible. Perhaps some previous ownef tried and succeeded to block it, or it is blocked by a mass of old grease or dirt...

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PostPosted: Mon Apr 15, 2019 7:41 am 
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Quote:
... turning the knobs against each other is impossible ...
Not against ... away from each other - as in untighten

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PostPosted: Mon Apr 15, 2019 8:10 am 
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Yes, this is what I have been trying to do. The right knob towards me, the left knob away. In other terminology: the right knob CCW, the left knob CW when viewed from the right side of the microscope. Does not move at all.

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PostPosted: Mon Apr 15, 2019 8:27 am 
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Hi 75RR,
I didn't see the atattchment at first because I read the thread on my smartphone. Thank you for posting it! Do you know if the Universal and Photomikroskop are supposed to work this way too? I thought that the WL and the big stands would share the same focus block design.

I had apart 3 GFL, most or all were Zeiss Winkel GFLs, so quite early ones. There clearly were differences, most visible was the nosepiece revolver. The oldest version was more rounded and had a matte surface. The design of the later nosepiece revolver was a lot better.

I atattch some pictures: Old Zeiss Winkel GFL and tool for removal of holding ring for the fine adjustment gears. This holding ring needs a lot of torque to loosen so you will need a strong tool. A machinst will be able to make one with my pictures and the microscope in front of him. The steel bar is just glued in with epoxy.
Before turning the holding ring a small setscrew has to be reomoved!

My fine focus shaft knobs have a set screw on one of them.

Zeiss


Attachments:
ZW Feintrieb und Haltering.jpg
ZW Feintrieb und Haltering.jpg [ 450.16 KiB | Viewed 155 times ]
Zeiss Winkel GFL Triebblock 1.jpg
Zeiss Winkel GFL Triebblock 1.jpg [ 486.31 KiB | Viewed 155 times ]
Werkzeug Ausbau Feintrieb 3.jpg
Werkzeug Ausbau Feintrieb 3.jpg [ 482.49 KiB | Viewed 155 times ]
Werkzeug Ausbau Feintrieb 2.jpg
Werkzeug Ausbau Feintrieb 2.jpg [ 455.13 KiB | Viewed 155 times ]
Werkzeug Ausbau Feintrieb 1.jpg
Werkzeug Ausbau Feintrieb 1.jpg [ 328.14 KiB | Viewed 155 times ]
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PostPosted: Mon Apr 15, 2019 8:28 am 
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Oh well ... would have been nice if it had worked on your GFL

Quote:
Do you know if the Universal and Photomikroskop are supposed to work this way too? I thought that the WL and the big stands would share the same focus block design.
As far as I know the WL shares the same focusing mechanism (block) with the Universal and the Photomicroscope, it also shares the same quick release stage and condenser holders.

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Last edited by 75RR on Mon Apr 15, 2019 8:36 am, edited 2 times in total.

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PostPosted: Mon Apr 15, 2019 8:28 am 
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more pics


Attachments:
Halteschräubchen Haltering Feintrieb.jpg
Halteschräubchen Haltering Feintrieb.jpg [ 387.48 KiB | Viewed 155 times ]
Klemmschrauben Feintrieb.jpg
Klemmschrauben Feintrieb.jpg [ 437.28 KiB | Viewed 155 times ]
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PostPosted: Mon Apr 15, 2019 9:22 am 
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Hi Bob,
Questions:
I see complete disassembly of the Winkel block. Including the roller bearings ?
What part of the mechanism adjusts the friction of movement ?
Is there a way to adjust without disassembly ?

Notes:
The Winkel mechanism in your pics is somewhat different from mine, but maybe is based on the same principles.
The special tool you fabricated for the ring is indeed the best design. I have used a similar tool in another mechanical task. On top of the cylinder, there was a 12mm(L)x12mm(W)x8mm(H) square bump or protrusion, for gripping with a socket wrench or an adjustable spanner, for tightening a large ring.

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Last edited by Hobbyst46 on Mon Apr 15, 2019 12:11 pm, edited 1 time in total.

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PostPosted: Mon Apr 15, 2019 11:58 am 
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75RR wrote:
As far as I know the WL shares the same focusing mechanism (block) with the Universal and the Photomicroscope, it also shares the same quick release stage and condenser holders.
On a post from 1915 in Photomacrography forum, a post by KurtM, forum member Eddie has stated that:
"The two WL (Black and White) you can see in the second picture above. They are considered the small research scope since it has the same focus block as the large research stands the Universal/Photomicroscopes and they have the quick release/quick mount stage and condenser which is interchangeable with the large research stand. Below is the black WL alongside a couple of Photomicroscopes and a Universal. The large research scopes are quite large and take up a lot of room." On my GFL, the stage carrier (and condenser rack) are fixed to the arm with screws, not a quick-detach knob, in contrast to the larger Zeiss Standards.
(http://www.photomacrography.net/forum/v ... hlight=gfl)

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PostPosted: Mon Apr 15, 2019 12:06 pm 
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No roller bearings on this Zeiss Winkel GFL! The two guides are both brass dovetails.
The coarse focus is adjusted with the separate collar. I don't know whether there is a fine focus adjustment at all. To me it seems a bit like an emergency-solution to adjust the fine focus this way. The brass guides should always provide enough friction to keep the stage at height.

The earlier Standard Juniors also had brass guides, the later versions "Chromleiste" hat roller bearings like the later Standard RA and 14-18.
These early post war Zeiss West instruments were not yet as bullet proof as the later instruments. The sold vast amounts and improved the design soon.

I have a Phomi, first version, second type from 1961 on, but I haven't had time to do anything with it yet. The fine focus has a bit more friction than I would like so maybe the knob-twist-trick is just what I need to get it going.


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PostPosted: Mon Apr 15, 2019 1:46 pm 
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Some more indirect information (not a Zeiss publication) on the fine focus adjustment on the Zeiss Universal (I imagine that includes the Photomicroscope as well)

See particularly Part 1 #1

http://asiimaging.com/docs/zeiss_universal_zdrive


Attachments:
FFK.jpg
FFK.jpg [ 31.14 KiB | Viewed 124 times ]

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PostPosted: Mon Apr 15, 2019 2:03 pm 
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Hobbyst46 wrote:
I am trying to refurbish and bring life to a very old Zeiss GFL stand, that was so far stored in a remote cupboard. There are two issues with it. One, regarding the field aperture assembly, will be described in a future post. The other challenge is the fine focus mechanism. The fine focus control functions but is too stiff and requires much more force than the normal. The coarse focus is fine. I suspect that the problem is due to old hardened grease.
Some time ago, a kind forum member has uploaded a link to a draft of a concise record, including sketches, written by his father, of disassembly and repair of the fine focus mechanism. I apologize for having forgotten the name of the poster - hopefully he will read this post and reappear! I followed the first steps as described, dismantled and separated the focus mechanism from the microscope arm, as shown below. Identifications and notations of parts are cited from the above record as far as I understand them.

The focusing gear moves the thin push-rod that in turn pushes the block against a stopper spring (photo(1), marked "Spring", and photo(3), left side of the block). The gear is actually hidden from sight by the block. The red circles symbolize invisible rollers that are caged within Vee-shaped grooves. The end of the push-rod itself is connected with a thin wire spring (photo (3), right side of the block, hardly visible). In the end face near that end of the push-rod, there is a retaining ring (photo (4)). It is locked with a side screw (not directly visible). That end face is touching the base plate of the whole assembled microscope. The face opposite the block is the female dovetail of the coarse focus, not related to the problem.

Complete disassembly of the mechanism appeared tricky. The heads of six screws are "locked" with red Loctite, against tinkering by amateurs (me). I tried to go around it. Yet, drops of light machine oil into the ends of the Vee-shaped grooves, from the outside, made no difference. Removal of the end plate, cleaning and re-greasing the stopper spring (photo(3))did not help. Tinkering with the two bolts was futile - hopefully it did not worsen the situation. I did not try WD-40, nor heat: this gizmo is a combination of brass and steel parts, and each has its own expansion coefficients.

Further dismantling might require a custom pin-spanner to remove the retaining ring without deburring. But I am not sure that it will expose the problematic hard grease area.
So, what would you suggest to do next? thanks in advance for ideas! perhaps links to available maintenance manuals?


EDIT: the above mentioned draft record of the repair of a Zeiss GFL fine focus was written by C.J. Matthews and was later posted by Graham Matthews, can be downloaded from MICROMAGUS.NET August 2006.

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Last edited by Hobbyst46 on Tue Apr 16, 2019 6:50 am, edited 1 time in total.

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PostPosted: Mon Apr 15, 2019 2:13 pm 
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75RR wrote:
Some more indirect information (not a Zeiss publication) on the fine focus adjustment on the Zeiss Universal (I imagine that includes the Photomicroscope as well)...See particularly Part 1 #1
Thanks 75RR! so, there is a chance that loosening the left knob set screw will free the CW motion of that knob, such that the two-knob maneuvre can be accomplished... Actually I have already tried it (in vain) on the set screw of the RIGHT knob - simply because it was easier to do than the left knob set screw... both heads of those screws are already wounded by previous screwdrivers... We'll see!

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PostPosted: Mon Apr 15, 2019 4:02 pm 
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So, I filed a watchmaker's screwdriver until it fits inside the slot of the focus knob set-screw, and loosened the left knob set screw - but the knob itself cannot be turned when the right focus knob is static and secured. Loosened both set screws - still no change. This becomes a separate riddle: what is the function of these knob set screws ? Perhaps pressing with a lever rod against the larger knob (the coarse focus knob) can help to push the fine focus knob outside, if the knob is slipped on the shaft rather than screwed on it.(?) :?
Bottom line
The above questions and discussion are now academic. The roller bearings can be serviced, but the fine focus gear itself is very delicate, the teeth on the lever that raises and lowers the block, as well as the teeth on the shaft that directly rotates that lever, are badly worn or broke. My findings are essentially the same as those of C. Matthews on his microscope. Until some miracle happens, this will be a purely coarse focus microscope...

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