Nikon Model S/G tension issue

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Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Nikon Model S/G tension issue

Post by Pitufo »

Does anyone by chance have experience with the old Nikon black enamel model G microscope (or possibly a model S)?

The problem is a stage which falls under gravity i.e. the focus is drifting. There is a tension dial but moving this to maximum tension does not resolve the problem.

As always, any suggestions much appreciated.

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Image

zzffnn
Posts: 1896
Joined: Thu May 22, 2014 1:25 pm
Location: Houston, Texas, USA
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Post by zzffnn »

I don't know for sure, but I have repaired a dropping Nikon focus block with focus mechanism similar to Optiphot/Labophot. Mine had a cracked fine focus gear (that is made of nylon). I replaced it with another fine focus gear and everything works normally again.

I read on MicUK that Nikon model S/G also has nylon fine focus gear that tends to crack when aged.

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Many thanks zzffnn, yes I found this very useful article on the nylon focus gear. I will take it apart an see if that is the problem. It looks quite expensive to get a replacement.

http://www.microscopy-uk.org.uk/mag/ind ... nikon.html

Here's another interesting article on this model in case it is useful for anyone https://acornabbey.com/blog/?p=8137

Here is the link for obtaining replacement focus gear http://www.microscope-maintenance.com/SpurGears.html

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Well some good news - the nylon gear is still in perfect condition (and I think this has been used in a university undergraduate lab for the best part of 50 years!).

I am going to continue stripping the mechanism down and see if I can get any answers..

EDIT: so I removed fine focus controls from both sides as per the Micscape article above, so that that main spindle (indicated with an arrow) can be pulled out. Care - there are two washers on other side (right hand side, RHS) from the side shown on this photo.

Image

I also removed screws 1, 2 and 3 which allows another brass gear to be removed on left hand side (didn't appear to help much)

Image

Photo of RHS showing washer position in red (the washers seem to be the opposite way round to that shown in Micscape) and screws which can be undone in blue.

Once I got to this position, I couldn't seem to get much further, so continued to play with the tension control to see what would happen. Lo and behold it was now free and could be moved much further (the range was very limited previously). It also now seemed to be putting real tension on the focus.

So I reassembled and hey presto, it seems to work perfectly...

I have no idea why it was successful, but it may be worth a try if someone encounters the same problem.

zzffnn
Posts: 1896
Joined: Thu May 22, 2014 1:25 pm
Location: Houston, Texas, USA
Contact:

Post by zzffnn »

Nice work and congratulations.

Disassembly and reassembly has also mysteriously fixed my other scope as well.

In US eBay, it is actually not expensive to buy a Nikon S/G scope/part for good price, if one is patient.

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