Repairing Nikon S mechanical stage

[zzffnn]

Thank you very much for helping.

The mechanical stage of my Nikon S microscope looks exactly like these two (except it say "EPO Germany"):
http://www.ebay.com/itm/Nikon-Microscop ... Sw3xJVXKjh
http://www.ebay.com/itm/Nikon-Microscop ... SwPgxVL2hR

The Y axis movement of it was too loose - when I held the Y axis vertically, it will drop quickly with its own weight. In use, it could not effectively move slide oiled to condenser with Type B Cargille (high viscosity) oil. In comparison, X axis has been tight and perfect.

I cannot remember exactly what I did to it. I am guessing its Y axis might be too tight when I bought it, so I put too much (light) white petroleum jelly in it, which made it too loose. I did not find any tightness/torque control mechanism and I looked at it at least twice. The last time I did, which was yesterday, I tried all screws and controls to the point that I dislodged the two bal bearings for the Y axis. I went even further and took apart almost everything down to that bare silver coaxial control shaft, but still could not find any torque control.

The only thing I did not touch and was not sure about was that silver coaxial control shaft. It has a tiny screw between the X and Y axis knobs, whose tightness change did not seem to affect anything. I also did not open up the bottom of that shaft (please see photo #2 of the following listing), which may (or may not) be hiding the torque control?
http://www.ebay.com/itm/Nikon-Microscop ... Sw3xJVXKjh

I would like to know what to do to tighten up the Y axis next time - I might try to put everything back but am not sure, as those two ball bearings look difficult to put back. Is the torque only regulated by heavy damping grease? I read a few Nikon S manuals but did not see assembly instruction.

Thank you again!

[zzffnn]

Anyone? Lorez, Phil, or Charles?

I think AO Spencer Sixty/Fifty/One Fifty use highly similar mechanical stages.

I don't mind buying another stage. It is just money right But I would hate to have the same unrepairable torque problem again (if it is a common problem). An eBay seller may not know, since this torque problem does not render the stage unusable (one won't know unless he/she uses the stage on a scope looking at a slide oiled to condenser), but it renders it VERY unstable.

[75RR]

It occurs to me that removing the "(light) white petroleum jelly" might be worth a try. i.e. De-greasing it.

[zzffnn]

Thank you, 75RR.

I would have to dissolve the petroleum jelly first, maybe with Xylene, which I do have. Then apply heavy damping grease, which I do not have. What is that brand/catalog number mentioned previously, by Charles or Phil?

Anyone else?

[75RR]

Not sure if you mean this one:

http://www.ebay.com/itm/400977183954?_t ... EBIDX%3AIT

[zzffnn]

Yes! Thank you. The "heavy" one is what I need.

[lorez]

There is no adjustable torque control on this stage. Each drive must be individually set. Changing the grease will not solve the problem.

Sorry I'm not around much any more.

lorez

[zzffnn]

Thank you very much, Lorez.

In view of your comments, I wonder what is the chance of getting a loose stage again, if I buy another one (is it a common problem)?

I had the suspicion that it came to me like that, though I was just not sure until reading your above comment. I did not test condenser immersion when the stage first came to me. The loose Y axis only reals itself with condenser immersion, but when it does show up it makes moving slides on Y axis very difficult.

Most of the times, I don't fix things (like putting on white petroleum jelly), unless I cannot use it. So the grease there might not come from me.

Does Nikon Labophot 2's stage has torque control mechanism built-in? Mine has been running fine, but it would be nice to learn.

Thank you a again!

[Charles]

Late to the party but...

If it is like the AO stages, you have some adjustment where the rack is screwed into the stage. Unscrew the screws along the rack and then while holding it tight to the pinion, screw the screws back in. I use a regular screwdriver to help move the rack over as I screw in the securing screws.

[zzffnn]

Thank you, Charles.

I did remember trying those rack holding screws yesterday. They were very tight to begin with (no room to make them tighter). Unscrewing those took quite a bit of effort. When I did, I let loose two ball bearings and things went apart. I would have to put the ball bearings back first if I want to give them another try.

[Charles]

Are you able to move the pinion (the gear that engages the rack) closer to the rack. Can you show me a picture of the underside of your stage.

[zzffnn]

Thank you very much, Charles.

I will try it again. I understood what you meant (and it makes sense).

I just need to overcome my fear of putting back those two ball bearings. There is one ball bearing above the rack and one below the rack, each holding about 8 tiny metals balls. I may need another pair of hands to help me.

Now my stage is in pieces and I don't have it with me at the moment. I will give it a try in a few days.

Edit: one thing in favor of Lorez' opinion (that torque was set in factory not adjustable easily) is that the bare pinion shaft feels loose in the Y axis control. I tried it without the rack. To make the pinion shaft tight, I would have to open it further, which I am afraid to.........and I am not sure if it can be done easily.

[Charles]

Use grease to hold the bearings in.

[zzffnn]

Will do! It is funny, as I just thought about that after typing in my last post (were you using Jedi mind tricks on me remotely - over the internet )...... Thank you so much!!

[lorez]

Are you able to move the pinion (the gear that engages the rack) closer to the rack.

If the rack and pinion are not properly spaced there will be backlash if they are too far apart and increased drag if they are too tight. Squeezing the rack and pinion together is not the recommended solution for a slide holder that is too loose.

There are spring washers on the shafts of the coaxial controls that apply the desired resistance to each of the axial controls and each must be separately adjusted. A light to medium grease works well, but not one that is tacky. Unfortunately, the easy user adjustable controls did not become available on the Nikons until the E series.

lorez

[zzffnn]

Thank you, Lorez.

That was why I said my coaxial control shaft felt loose by itself on the Y axis, without rack attached.

Charles' comments are still very helpful, as I may attempt to use the pinion part from a very similar stage (from AO One Fifty) for the Nikon S.

[zzffnn]

I fixed it, by combining two broken stages (one from from Nikon S, the other from AO One Fifty). X and Y torque is now perfect.

But the Y axis now goes too far to one side and not enough to the other. I probably put in the ball bearings at the wrong position? I will try again tomorrow, if I get a chance.

Charles, for this particular stage. Rack is held onto pinion by ball bearings, so there is not much torque regulation there. I had to use Tue good Y axis from AO One Fifty to fix that of my Nikon S.

Overall, the stage is perfect for low viscosity oil immersion. But still not good enough for high viscosity oil immersion. Probably due to design imperfection and used gear not being in best possible shape. My Nikon Labophot 2's stage is better and good enough for high viscosity oil immersion.

[lorez]

Rack is held onto pinion by ball bearings

I've never seen this. Is a photo possible ?

lorez

[zzffnn]

Sorry, I meant rack is screwed onto gear, then rack/gear assmebly is held onto pinion with two ball bearings (above and below the gear). I will take a photo when I get to it tomorrow evening.

[zzffnn]

Sorry for the poor image quality. I took photos with phone in one hand, while holding the repaired assembly with the other. My family members were taking nap so I did not try to make lighting better.

I took apart stage again and put in the ball bearings again. It seemed to get a little better, though still stopping 2-3 mm before the perfect position. I am going to stop here, as putting in ball bearings is not fun.

In the bottom photo, you can kind of see the top ball bearing where my thumb tip was. The top ball bearing holds a black rack onto the pinion. The black rack in that photo has gear and screw holes. A silver rack screws onto the black rack. A bottom ball bearing holds the silver rack.

In the other photo, you can see the bottom ball bearing going in under the silver rack.