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Cleaning a Nikkor-H 50/2
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PostPosted: Sat Aug 03, 2013 7:03 pm    Post subject: Cleaning a Nikkor-H 50/2 Reply with quote
Does anyone know how to open a Nikkor-H 50/2? I want to remove some fungus from the first (front) element.


PostPosted: Sat Aug 03, 2013 7:19 pm    Post subject: Reply with quote
First remove the Name Ring. I can't remember if name ring holds front element in place or if there is another ring under the name ring...in any case how to proceed after name ring is removed is obvious...

Last edited by visualopsins on Thu Aug 08, 2013 7:40 pm; edited 1 time in total


PostPosted: Wed Aug 07, 2013 4:26 pm    Post subject: Reply with quote
this may help:
http://rick_oleson.tripod.com/index-102.html


PostPosted: Thu Aug 08, 2013 4:30 pm    Post subject: Reply with quote
Remove the single grub screw located on the face of the name ring. Set the focus to 0.6m, then grip the front nosepiece with a wide rubber band and unscrew it counter-clockwise. The nameplate, filter threads and nosepiece securing the lens unit comes off as a single piece. You can then tip the lens forward carefully and remove the entire lens unit, or you can use a spanner to just unscrew the front group, leaving the lens unit in place. I recommend just removing the front group.

The fungus is probably on the back surface of the front group. If not, you'll need to dismantle the front group to get inside and clean it.


PostPosted: Sat Aug 10, 2013 1:09 pm    Post subject: Reply with quote
Thanks for the tips.

I unscrewed the grub ring in the namering and then used rubber gloves to screw the nose off the lens, with namering and all.
It took some strength but it's easy enough.

Then you can lift the entire optical block out.

Now I don't see how to remove the front optical block, or the front lens.

Outside the front lens there are two rings, I marked one with a yellow arroiw and one with a two red arrows.
But which one do I unscrew, and how?
There is not enough place to grip the ring with the red arrows.
The ring with the yellow arrow is too deep inside the lens to grip with your fingers, and I don't have a special tool.

Also there is a mysterious screw, marked with a green arrow.

Using a big knife I managed to unscrew it just a bit but it won't come out any further, just rotates in it's place...

Any ideas?



PostPosted: Sat Aug 10, 2013 2:08 pm    Post subject: Reply with quote
Ultron wrote:

Outside the front lens there are two rings, I marked one with a yellow arroiw and one with a two red arrows.
But which one do I unscrew, and how?
There is not enough place to grip the ring with the red arrows.
The ring with the yellow arrow is too deep inside the lens to grip with your fingers, and I don't have a special tool.

Also there is a mysterious screw, marked with a green arrow.

Using a big knife I managed to unscrew it just a bit but it won't come out any further, just rotates in it's place...

Any ideas?


You need to unscrew the outer ring (red arrows) to remove the front group from the housing. If there are no slots for a spanner, you'll need a friction disc to grip it and unscrew it (ccw). If after removing the front group you find the fungus is not on the exposed element at the back of the group, you will need a tool to unscrew the ring indicated by the yellow arrows to remove the first element.

You should have left the screw indicated by the green arrow undisturbed. It is an eccentric adjustment screw used to fine tune (calibrate) the aperture opening. It fits in the slot at the top of the inner helicoid sleeve (visible in your photo at far left). Now you have an additional problem. Wink


PostPosted: Sat Aug 10, 2013 2:33 pm    Post subject: Reply with quote
Hm they should put a warning on those screws Sad
Well I'll just screw it back in then.
The rear group unscrews easily from the optical block, so I just removed that and then I could clean the backside of the front optical group.
That got rid of most of the fungus, but there is also some fungus on the front lens, so I will see if I can find something to put some friction on the second ring and unscrew that.

If I can't I'll just leave it and put it back together, it is just some fungus at the edges, so not too serious.


PostPosted: Sat Aug 10, 2013 5:57 pm    Post subject: Reply with quote
Hm while trying to get the second ring unscrewed I accidentally unscrewed the front lens group.

But it seems the mystery screw is not connected to anything, looks like it only keeps the front group in place.



I can not get the second ring unscrewed.
I improvised a friction tool from a fitting bottle cap and pieces of rubber from my rubber gloves but the ring is too tight, I don't think anyone can unscrew this. I'd say this front lens is uncleanable Sad


PostPosted: Sat Aug 10, 2013 8:15 pm    Post subject: Reply with quote
Ultron wrote:

But it seems the mystery screw is not connected to anything, looks like it only keeps the front group in place.

I can not get the second ring unscrewed.
I improvised a friction tool from a fitting bottle cap and pieces of rubber from my rubber gloves but the ring is too tight, I don't think anyone can unscrew this. I'd say this front lens is uncleanable Sad


No, the mystery screw (and it's no "mystery") does *not* keep the front group in place. Rolling Eyes Laughing

As I noted above, it is an eccentric adjustment screw. Rotate it and you will see that the head of the screw does not turn in a perfect circle, but in a slightly elliptical path. That's because the screw shaft is off-center from the head. As I noted above, when the optical block is in place and this screw head is sitting in the matching slot at the top of the helicoid sleeve, turning it rotates the entire lens assembly slightly in the sleeve to adjust the opening of the lens aperture.

With regards to the second ring (tapered cone) sometimes those spin out quite easily, and at other times you would think that Nikon employed gorillas to tighten them.

Sometimes a tapered rubber sink stopper of the right size will grip these and spin them out. And sometimes it won't. Regrettably that appears to be the case with your lens. Sad


PostPosted: Sun Aug 18, 2013 4:28 pm    Post subject: Reply with quote
OK thanks, with some tinkering I got the eccentric screw in a position where it will let the aperture open up all the way.
Putting the ring with the aperture back in was a bit tricky, here is how I did it:

Set the lever on the inner tube with the aperture to f 16, set te aperture ring on f 16, set the lever on the inner tube to keep the aperture open or close to open, push the handle on the lens mount to open the aperture, but the inner tube in the lens barrel and play with the aperture lever on the lens barrel until the inner tube drops in.

If the aperture won't open up all the way try a different position. It seems the screw has an influence on both levers, so don't break your head over it just try something.

I will leave the fungus on the front lens. This lens was already sharp, now that the fungus on the back of the front group is gone it may be even better. I don't think the fungus on the edges of the front element make much of a difference optically.

Maybe one day I will find a better friction tool.

Now that the lens is already open I might as well relube it, any tips for that?
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