MicrobeHunter.com Microscopy Forum

I have a question regarding the tension adjustment ring on my Olympus CHA:
It is unable to turn. It’s rock solid. No movement, not even a µ!
I’d like to adjust the course knob, as it needs — in my opinion — too much force to be turned. A bit less tension would be great.

In all the repair manuals I could find, is an opening mentioned to put a flat bladed screw driver in release the ring. Not so on my modfel. The ring is complete without any holes or grub nuts.
What’s the magic to release the ring?

I have extremely limited experience with Olympus microscopes and never used your model. However, would this be of some help?
viewtopic.php?f=5&t=8551&p=74051&hilit= ... ion#p74051

Leitzcycler wrote: ↑

Fri Jul 31, 2020 6:19 am

However, would this be of some help?
viewtopic.php?f=5&t=8551&p=74051&hilit= ... ion#p74051

I have read that thread. It addresses the same problem but the tension adjustment ring on my model is different.
It shows no gaps in the grooves where one could put in the tip of any kind of tool.
I am wondering if I have to use a set of pliers — but I don’t want to break it, of course.

HAL_9000 wrote: ↑

Fri Jul 31, 2020 9:56 pm

I am wondering if I have to use a set of pliers — but I don’t want to break it, of course.

Alan Wood is (see the Olympus site) very friendly and knowledgable - I would email him about this problem before bringing in the pliers and vices and other heavy artillery.

Thanks, Hobbyist46!
I will do that

[EDIT]
Done!

Those old CH scopes have a very similar coaxial focus mechanism to the Olympus BH2 scopes. I recently put a few videos on YouTube (search for my name, and you should find them). If you watch part 2 in the series, you will see why your tension knob was so hard to turn! You will also want it cleaned and regressed! Your mechanism is very similar to that in the videos, but not exactly the same. So if you ever decide to tear into it to fix it right, contact me first. Otherwise you can damage the mechanism, due to the "hidden" screw in the pinion assembly.

Carl Hunsinger

Thanks Carl!
It is a joy to look over your shoulders. I watched both videos and wait for part 3 now.
The tension ring on my CHA remains untouched as Alan Wood hasn’t replied to my message, yet.

There must be plenty of gunk inside the focus drive!
Seems that I need to prepare for a major clean'n'grease operation.

Very possibly your scope should have a complete teardown. But then again, how many 30 plus year old scopes don't?

As you can see in the Part 2 video, when I removed the tension adjustment knob, the grease inside was nearly solid. Yours is no doubt the same, and that's why you can"t turn it.

There is a hidden screw inside the pinion assembly that was eliminated from the BH2 design. Don t forget about that. This means you have to disassemble the pinion assembly to remove the ball bearings and the hollow pinion while the pinion assembly is still in the frame. Once that is done, you can remove the secret screw and remove the brass pinion carrier.

Carl

When it comes to cleaning, what solvents should be used? Acetone for metal parts and IPA for plastic?
And what type of grease is recommended?

Sorry for the questions — I’m new in this universe.

See the PDFs in this folder. They apply to the BH2.

https://drive.google.com/folderview?id= ... 9o8SWUOcys

I use mineral spirits and acetone for the metal parts. Acetone on the nylon washers. Don't use IPA on them, it will swell the nylon. Also, IPA can make white blotches on the black knobs. Don't ever get acetone on the black knobs!

Carl

Wow! Thank you so much, Carl!
I’ll study these documents over the weekend.