Right eyepiece droops

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
Post Reply
Message
Author
macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Right eyepiece droops

#1 Post by macnmotion » Tue Sep 27, 2022 6:39 am

Hi. When I spread my left and right eyepieces for my proper viewing width the left side stays still but the right side slowly drops all the way down due to gravity. I have no idea how these are constructed so I have no idea if I can tighten the right side or increase friction. This is a very old Nikon diaphot. Can anyone give me an idea if I can fix this? To get around it I leave the right eyepiece all the way down, turn my head to a funny angle and swing the left eyepiece up to a proper spread. But I'd rather not do that. Thanks.

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Right eyepiece droops

#2 Post by apochronaut » Tue Sep 27, 2022 11:42 am

The two optical sections of a Seidentopf head are tensioned by a combined effort between the central nut applying tension to the two coaxial sections and damping grease on the rotating surfaces. Usually, the inner or lower section of the right eyepiece receives slightly less pressure than the left. My guess , if there is not a cracked housing, is that the collar nut that tightens the system together plus possibly some drying out of the lubricant is the cause.
I assume that you have looked carefully in order to exclude the possibility of a cracked lower ( right) housing as the culprit? A crack could be concealed under the prism section of the left housing. A crack would also show as a slight looseness not evident on the left, if you wiggle each very lightly.
You can likely see up between the ieft prism section and the right hand collar with a flashlight.
Removing the left prism cover will allow a better view.

macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Re: Right eyepiece droops

#3 Post by macnmotion » Tue Sep 27, 2022 1:30 pm

Thanks for that detailed answer. I'm a newbie with a microscope so I'll have to figure out the best way to get to the parts you mention to see what may be wrong. To answer your question, I don't see a crack, but I haven't taken apart anything to look behind other pieces. There is a slight wiggle of the right eyepiece, but I'm not sure if that's because the collar nut may not be tight enough. The nut is currently in a position where the word Nikon is right side up, however I am able to continue turning the nut in a clockwise direction, seemingly tightening it, but I didn't go very far because then the Nikon name and the measurement lines are no longer right side up. I don't want to force anything. There is a website where someone has disassembled this microscope, I'll try sending a contact to him to ask if he can describe exactly what I should take apart. I'd hate to start undoing things without knowing what I'm doing and end up making the system inoperable.

Greg Howald
Posts: 1185
Joined: Tue Oct 20, 2020 6:44 am

Re: Right eyepiece droops

#4 Post by Greg Howald » Tue Sep 27, 2022 2:50 pm

I had this problem with a new scope once. It took a while for me to find that tiny screw on the occular tube which needed tightening. Take your time. Look carefully.

macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Re: Right eyepiece droops

#5 Post by macnmotion » Tue Sep 27, 2022 4:30 pm

Greg Howald wrote:
Tue Sep 27, 2022 2:50 pm
I had this problem with a new scope once. It took a while for me to find that tiny screw on the occular tube which needed tightening. Take your time. Look carefully.
Thanks, I'll go through it carefully. Appreciate your input.

Greg Howald
Posts: 1185
Joined: Tue Oct 20, 2020 6:44 am

Re: Right eyepiece droops

#6 Post by Greg Howald » Wed Sep 28, 2022 3:38 am

If you haven't found the answer to this yet, please give brand and model number of the scope. More help may be available through personal experience of others.

macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Re: Right eyepiece droops

#7 Post by macnmotion » Wed Sep 28, 2022 4:02 am

Greg Howald wrote:
Wed Sep 28, 2022 3:38 am
If you haven't found the answer to this yet, please give brand and model number of the scope. More help may be available through personal experience of others.
This is a Nikon Diaphot Inverted Tissue Culture Microscope, circa 1985-ish, with a Siedentopf-design binocular head built onto a die-cast body. A focusing Bertrand Lens was built into the binocular body for fast alignment of the phase annular ring. A dark slide position was incorporated in the turret to cut off stray light from the optical system during time lapse cinemicrography as well as a low-power focusing magnifier for critically sharp photomicrography with the 2x and 4x objectives.

You can see the microscope model here:
https://www.microscopyu.com/museum/diap ... microscope

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Right eyepiece droops

#8 Post by apochronaut » Wed Sep 28, 2022 11:17 am

Just curious. If you just lift the right eyepiece tube, does it just drop back down?

Phill Brown
Posts: 603
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: Right eyepiece droops

#9 Post by Phill Brown » Wed Sep 28, 2022 12:13 pm

Possibly missing a set screw under one of the side covers.
Could be the set screw has sheared off by being dropped.

macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Re: Right eyepiece droops

#10 Post by macnmotion » Wed Sep 28, 2022 3:13 pm

apochronaut wrote:
Wed Sep 28, 2022 11:17 am
Just curious. If you just lift the right eyepiece tube, does it just drop back down?
If by "lift" you mean swing counter clockwise to spread it away from the left eyepiece, then yes, it drops back down. Without the eyepiece in the tube, it drops more slowly than with the eyepiece in the tube, but that's to be expected.

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Right eyepiece droops

#11 Post by apochronaut » Thu Sep 29, 2022 2:55 pm

Usually the tensioning or clutching on those is by virtue of an actual clutch in the form of a compressible wave washer plus surface tension created by the damping grease : both in the clutch areas and around the central sleeve itself. The tension should be applied evenly to both the left and right collsrs by the clutch and the damping grease should be equally effective on both sides.
While I have not pulled one the same as yours apart, here are some possibilities that might cause such a problem.
1) While I don't recall ever seeing one with a lock screw, maybe Greg could give you an idea how that one he encountered worked. That would imply a double walled collar with the exterior prism/mirror housing locking to an inner collar that did the rotating. I have not seen that but that kind of head is open to all kinds of design variables.
2) The design I am most familiar with uses a cluch plate on the bottom of the central column which when tight acts on the right rotating collar, forcing it against the bottom surface of the left collar which in turn acts on a large wave washer at the top, compressing it under that central cap between the eyepieces. That creates a clutch top and bottom. Those collars are very thin and aluminum. If the grease became dried out and stiff in the past two scenarios might have taken place. The mechanism might have been oiled and too much might have been introduced to the lower(right) collar destroying the clutching action of the grease. Another possible option is that forcing them to rotate, cracked the lower one.The crack could be concealed under the left prism housiing.

Any way, if you remove the intrrpupillary section from the deviating prism section , it should give you some ideas. Hopefully, it is just a question of the tension screws on the clutch just being loose. Usually it is attached with 3 or 4 screws, locating the beamsplitter prism section over the deviating prism.

One big clue without taking it apart is whether the left eyepiece section is acting normally or not as well. Does it rotate smoothly and predictably, is it qiite stiff or is it a little light in tension and maybe just barely staying in place by itself?

Phill Brown
Posts: 603
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: Right eyepiece droops

#12 Post by Phill Brown » Fri Sep 30, 2022 1:15 pm

Too many guess work suggestions about grease and crush washers.
That's not how they work.
I have a few of the Nikon binocular heads which are easily serviceable.
Attempting the suggestion about tension washers will only result in a broken front cover cap.

User avatar
blekenbleu
Posts: 299
Joined: Tue Feb 25, 2020 5:55 pm
Location: South Carolina low country
Contact:

Re: Right eyepiece droops

#13 Post by blekenbleu » Fri Sep 30, 2022 2:14 pm

macnmotion wrote:
Wed Sep 28, 2022 4:02 am
Nikon Diaphot
A pair for sale: https://www.ebay.com/itm/165389187752
Metaphot, Optiphot 1, 66; AO 10, 120, EPIStar, Cycloptic

macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Re: Right eyepiece droops

#14 Post by macnmotion » Fri Sep 30, 2022 4:37 pm

Phill Brown wrote:
Fri Sep 30, 2022 1:15 pm
Too many guess work suggestions about grease and crush washers.
That's not how they work.
I have a few of the Nikon binocular heads which are easily serviceable.
Attempting the suggestion about tension washers will only result in a broken front cover cap.
Thanks. I'm leaning toward doing nothing. I primarily use this for photography and use my TV as an external monitor for viewing and focusing. If I want to use the eyepieces, I can leave the right side all the way down and slide up the left, rotating my head just a little bit. Not ideal but for the rare times I'll use the eyepieces it's fine.

Phill Brown
Posts: 603
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: Right eyepiece droops

#15 Post by Phill Brown » Fri Sep 30, 2022 7:04 pm

The 2 side covers are only held by 4 JIS screws.
Nothing optical is affected by removing the plastic covers.
Check both slotted set screws are in place,if they are both there one may have sheared off the bottom end. The thread is maybe 2mm so it wouldn't be that hard to break.

It's worth checking as it's a 5 minute job.

Greg Howald
Posts: 1185
Joined: Tue Oct 20, 2020 6:44 am

Re: Right eyepiece droops

#16 Post by Greg Howald » Fri Sep 30, 2022 10:11 pm

Hi Mac. I suggest you do what Phil suggests. Go the distance it may well be the cure and can't hurt anything to try. :)

macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Re: Right eyepiece droops

#17 Post by macnmotion » Sat Oct 01, 2022 2:59 pm

Phill Brown wrote:
Fri Sep 30, 2022 7:04 pm
The 2 side covers are only held by 4 JIS screws.
Nothing optical is affected by removing the plastic covers.
Check both slotted set screws are in place,if they are both there one may have sheared off the bottom end. The thread is maybe 2mm so it wouldn't be that hard to break.

It's worth checking as it's a 5 minute job.
OK, that I think I can do without breaking anything :-) I'll try this weekend.

Post Reply