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Anatomy of an Olympus CHT focus/condenser block
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19905
Location: Richland, Washington State, USA

PostPosted: Mon Mar 02, 2015 1:47 am    Post subject: Reply with quote

MaxRockbin wrote:
Rik, with the CH-T, what do you think of the idea of leaving the condenser rack in place and mounting the camera on top of it?

I do not like the idea of mounting the camera on the condenser rack. At least on my unit, that seems not very rigid, and hard to make rigid.

However, I'm gradually coming to feel better about the scheme of using a filler block, no need to cut anything off, and in fact those stage mounting tabs could come in handy. That needs to sit in my head for a while.

Quote:
You mentioned that you don't have the manual for this scope. I'm sure you have the generic CH repair manual, but for completeness and posterity...

Correct. I do have that one, but it does not address this style of focus block.

--Rik
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Choronzon



Joined: 21 Feb 2010
Posts: 384
Location: Chicago USA

PostPosted: Mon Mar 02, 2015 5:19 am    Post subject: Reply with quote

Nope, I was wrong, the Zeiss focus blocks with the plastic knobs have only 2mm fine travel, just like the metal knob ones. It's the standard series that have the entire travel of the fine adj on the bearing block, and those require cutting up to be useful, although they are cheap. The Ortholux II does have 30 mm travel on the fine, and the Orthoplan has 40mm travel. These two just unbolt and can be adapted for motorization.
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Choronzon



Joined: 21 Feb 2010
Posts: 384
Location: Chicago USA

PostPosted: Mon Mar 02, 2015 5:39 am    Post subject: Reply with quote

If you can find a Nikon Biophot, Metaphot or Fluophot stand for cheap that has the plastic knobs, not the metal ones, the whole focusing mount unbolts from the back of the casting and also has full fine adj travel at 100 microns per rev.
They're harder to find, but the bearing block is massive and uses roller bearings arranged in a V for stability. The metal knobbed Biophots have the dreaded cracking spur gears made of plastic.
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lothman



Joined: 14 Feb 2009
Posts: 373
Location: Stuttgart/Germany

PostPosted: Mon Mar 02, 2015 12:14 pm    Post subject: Reply with quote

Choronzon wrote:
The metal knobbed Biophots have the dreaded cracking spur gears made of plastic.


I had the same problem (cracked pinion gear) on a Nikon Labophot 2 and
replaced the gear with a metal Version lot of work. Today I would avoid those old Nikon types.
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Chris S.
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Joined: 05 Apr 2009
Posts: 3265
Location: Ohio, USA

PostPosted: Mon Mar 02, 2015 9:48 pm    Post subject: Reply with quote

As a contrasting opinion, the Nikon Labophot 2 blocks are my personal favorite, with the Labophot a very solid second favorite (and easier to integrate). The plastic gear was surely a design choice intended to protect the block--it holds up very well through time, but will sheer if the focus knobs are subjected to undo pressure, sparing the other elements of the block. I'm picky about the focus blocks I buy, and through at least least two dozen good Nikon blocks--and a few bad ones that I've returned--have found that if the block has not been forced against something like hardened gear grease, the sacrificial plastic gear is sound.

Cheers,

--Chris
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lothman



Joined: 14 Feb 2009
Posts: 373
Location: Stuttgart/Germany

PostPosted: Tue Mar 03, 2015 5:51 am    Post subject: Reply with quote

Chris S. wrote:
.... I'm picky about the focus blocks I buy, and through at least least two dozen good Nikon blocks--and a few bad ones that I've returned--have found that if the block has not been forced against something like hardened gear grease, the sacrificial plastic gear is sound.

Cheers,

--Chris


I agree that the Labophot mechanics are well made beside the plastic pinion and the screws made from very soft material.

I have one old Nikon microscope at work and one I bought from ebay, both showed the broken plastic gear. So my ratio is much worse than yours ;-) But I often see those old microscope stands going off for 35-90$ in the US, shipping and tax to Germany is about 100$ Sad .

Perhaps we should install a spare part exchange here in the forum. I could do a bunch of the metal gears which can easily be glued in place on the rod of the fine focus.

Or even better, we need a source for an affordable focus block from new production. I think Nikon, Olympus... don't produce their focus blocks them selve. Dear chinese focus block manufacturers please give us a sign Laughing
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