BH-2 Focus adjustment question

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david_b
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BH-2 Focus adjustment question

#1 Post by david_b » Mon Jan 13, 2020 9:12 am

I have a BH-2 and would like to adjust the tension on the focus knob.
According to the manual, this is achieved by inserting a screwdriver into one of the holes on the adjustment ring.
On the unit I have here, the screwdriver can only be inserted a few mm and there is insufficient leverage to move the ring at all.
How do I adjust the focus tension?

Image

MichaelG.
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Location: NorthWest England

Re: BH-2 Focus adjustment question

#2 Post by MichaelG. » Mon Jan 13, 2020 10:32 am

david_b wrote:
Mon Jan 13, 2020 9:12 am
I have a BH-2 and would like to adjust the tension on the focus knob.
According to the manual, this is achieved by inserting a screwdriver into one of the holes on the adjustment ring.
On the unit I have here, the screwdriver can only be inserted a few mm and there is insufficient leverage to move the ring at all.
How do I adjust the focus tension?

Image
... With great difficulty and considerable finesse :D

Seriously though: A plain shaft without the screwdriver tip should give you a much better chance.

MichaelG.
Too many 'projects'

PrecisionInstruments
Posts: 47
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Location: Perth, Western Australia

Re: BH-2 Focus adjustment question

#3 Post by PrecisionInstruments » Mon Jan 13, 2020 11:42 am

A tight fitting pin punch works well, or a 3mm Allen key.
The lubricant would have become dry, gluing the collar in place.
There is also a gear box in the back of the stand, behind the panel on rear of stand held on by four small Phillips screws, which will most likely be seized up as well. The gears in this box will become damaged if too much force is applied to adjust focus. This gear box can be removed simply by four 2.5mm screws, soaked in a solvent to dissolve dry lubricant, hit with a wire brush, oiled, and replaced. Careful to get the teeth of gear box and rack in mesh when reinstalling.
Should come up like new 👍🏼
I have a headache, For which the future’s made

david_b
Posts: 151
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Re: BH-2 Focus adjustment question

#4 Post by david_b » Mon Jan 13, 2020 2:02 pm

Thank you both; the allen key worked perfectly and I can now adjust the tension. It seems to require more turning than I expected to make a small change in tension.
Anyway, the reason I was wanting to free the adjustment ring is there is a small but annoying problem with the fine focus.
Hard to describe, but if you turn the fine focus a certain amount in one direction, then back again by the same travel, you would expect to arrive back where you started, but this is not happening. In other words, the fine focus knob is moving the stage more in one direction than the other. I hope that makes sense. The coarse focus knob is operating as normal as far as I can tell.
I have not yet removed the back plate, pending any further opinions!
Thanks again

MichaelG.
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Re: BH-2 Focus adjustment question

#5 Post by MichaelG. » Mon Jan 13, 2020 4:11 pm

david_b wrote:
Mon Jan 13, 2020 2:02 pm
... Hard to describe, but if you turn the fine focus a certain amount in one direction, then back again by the same travel, you would expect to arrive back where you started, but this is not happening. ...
The technical term is ‘Hysteresis’ ... but that doesn’t tell you how to fix it !

My guess is that there is thickened grease in the motion-work and that gravity is assisting motion more in one direction than the other.

The quick fix would probably be to introduce a couple of drops of ‘PlusGas formula A’ or similar, which will thin the grease a little.

Longer-term : a strip and re-grease might be beneficial.

With best wishes for success
MichaelG.
Too many 'projects'

carlh6902
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Re: BH-2 Focus adjustment question

#6 Post by carlh6902 » Mon Jan 13, 2020 5:06 pm

If the focus is stiff, and especially if it has noticeable hysteresis, then the grease is thickened and the scope needs service. This folder contains two PDFs that describe how to fix the focus mechanism:

https://drive.google.com/open?id=1bUoWP ... XsLG0HW34d

Carl
--- If you're in the Kansas City area and you need help with an Olympus BH-2 scope, PM me. I love to work on these things ---

MichaelG.
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Re: BH-2 Focus adjustment question

#7 Post by MichaelG. » Mon Jan 13, 2020 5:17 pm

Great work, Carl

MichaelG.
Too many 'projects'

david_b
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Re: BH-2 Focus adjustment question

#8 Post by david_b » Mon Jan 13, 2020 5:30 pm

Thanks Carl
The tension can be adjusted so the coarse focus wheel is easy to turn - but when I do that the problem with the fine focus gets noticibly worse.
When I tighten the coarse focus to the max, the fine focus is better but far from perfect.
The fine focus adjustment itself is not stiff - the knob turns smoothly regardless of the tension.
After reading through those service schedules, it looks like a job for a specialist!

thomas.schwarz
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Re: BH-2 Focus adjustment question

#9 Post by thomas.schwarz » Mon Jan 13, 2020 8:32 pm

carlh6902 wrote:
Mon Jan 13, 2020 5:06 pm
If the focus is stiff, and especially if it has noticeable hysteresis, then the grease is thickened and the scope needs service. This folder contains two PDFs that describe how to fix the focus mechanism:

https://drive.google.com/open?id=1bUoWP ... XsLG0HW34d

Carl
Awesome! Thanks!!!

david_b
Posts: 151
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Re: BH-2 Focus adjustment question

#10 Post by david_b » Tue Jan 14, 2020 10:59 am

PrecisionInstruments wrote:
Mon Jan 13, 2020 11:42 am
There is also a gear box in the back of the stand....
carlh6902 wrote:
Mon Jan 13, 2020 5:06 pm
If the focus is stiff, and especially if it has noticeable hysteresis, then the grease is thickened and the scope needs service. This folder contains two PDFs that describe how to fix the focus mechanism:

https://drive.google.com/open?id=1bUoWP ... XsLG0HW34d

Carl

Thanks again for the help.
I have removed the gearbox.
The good news is the grease is not dry and does not seem to be particularly thick. I don't know how easily the gears should turn but they do turn smoothly if a little stiff. The focus block moves up and down easily and smoothly. It would fall very quickly under gravity if I let it. So I don't think thickened grease is the problem there.
The bad news is that the two brass shims - shown in Figure 7 of Carl's excellent guide - are missing.
Is this likely to be the cause of the fine focus problem? If so can these parts be obtained or would I have to get them made?
If the shims are not not likely to be the cause, then I will continue to dismantle further.
Thanks again!

Image Image

PrecisionInstruments
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Location: Perth, Western Australia

Re: BH-2 Focus adjustment question

#11 Post by PrecisionInstruments » Tue Jan 14, 2020 12:55 pm

Sometimes shims have not been applied. Depending on the backlash between gear box and rack which you can now see, some maybe applied to take up the excess slack. There should always be a small amount of play though.
The lubricant in the gear box looks like it requires replacing. It should spin quite freely, though not whizz around.
It would be suitable to soak in acetone (I use diggers shellite) to remove old lubricant, spin the gears and scrubbing with a brush. A drop of decent oil (sewing machine type) on each bushing will be sufficient. Doing that once a year will see it last a long time.
Now, if the lubricant there is getting old/tight, you can imagine what the rest of the focus system is like.
The original Olympus lubricant is Losoid 1160C, you might be lucky but I have to order it in 1Kg tubs. Though being a service tech, this any many other lubricants only lasts a year or two.
Last edited by PrecisionInstruments on Tue Jan 14, 2020 1:15 pm, edited 1 time in total.
I have a headache, For which the future’s made

PrecisionInstruments
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Re: BH-2 Focus adjustment question

#12 Post by PrecisionInstruments » Tue Jan 14, 2020 1:07 pm

Forgot to mention,
When reinstalling the gearbox, be careful to have the teeth mesh with the rack correctly (not on top of each other). Have the 2.5mm Allen screws slight loose, lift the focus block (or stage) up ever so slightly then tighten the screws. Sometimes the coarse focus can feel lumpy if the gear box is not at the right ‘height’, a few attempts may be needed.
I have a headache, For which the future’s made

david_b
Posts: 151
Joined: Wed Aug 28, 2019 1:07 pm

Re: BH-2 Focus adjustment question

#13 Post by david_b » Tue Jan 14, 2020 1:36 pm

PrecisionInstruments wrote:
Tue Jan 14, 2020 12:55 pm
Sometimes shims have not been applied. Depending on the backlash between gear box and rack which you can now see, some maybe applied to take up the excess slack. There should always be a small amount of play though.
The lubricant in the gear box looks like it requires replacing. It should spin quite freely, though not whizz around.
It would be suitable to soak in acetone (I use diggers shellite) to remove old lubricant, spin the gears and scrubbing with a brush. A drop of decent oil (sewing machine type) on each bushing will be sufficient. Doing that once a year will see it last a long time.
Now, if the lubricant there is getting old/tight, you can imagine what the rest of the focus system is like.
The original Olympus lubricant is Losoid 1160C, you might be lucky but I have to order it in 1Kg tubs. Though being a service tech, this any many other lubricants only lasts a year or two.
Thank you.
I would not say the gears are spinning freely, they offer quite a bit of resistance.
However, I can now see this is not the only cause of the problem. When I operate the fine focus knob, I can see that the horizontal silver coloured shaft seen at the bottom of figs 9, 10 &11 (behind the brass bar) is not rotating consistently. I suspect the nylon gears are slipping.
It looks like I will need to send the scope in for repair - that nylon gear cluster is beyond what I'm comfortable messing with!

PrecisionInstruments
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Location: Perth, Western Australia

Re: BH-2 Focus adjustment question

#14 Post by PrecisionInstruments » Tue Jan 14, 2020 2:02 pm

Not a problem.
It’s great that the gear box in intact and teeth have been stripped. I have only one original box left, and have had to machine up the gear that normally strips.
It is possible that the nylon gear in the planetary gear box has become defective. Luckily, the newer BX 1&2 series use the same parts and should still be available.
Quite easy to check first though - two thin black caps on the ends of the fine focus knobs come off (a nice scalpel can help pick them out). A 2.5mm Allen key in either end of fine focus knobs twisted opposed to each other will release side. The side that doesn’t come off will simply pull out. Planetary gears, along with small nylon gear on fine focus shaft, will be visible.
Good luck
I have a headache, For which the future’s made

david_b
Posts: 151
Joined: Wed Aug 28, 2019 1:07 pm

Re: BH-2 Focus adjustment question

#15 Post by david_b » Tue Jan 14, 2020 4:06 pm

PrecisionInstruments wrote:
Tue Jan 14, 2020 2:02 pm
The side that doesn’t come off will simply pull out. Planetary gears, along with small nylon gear on fine focus shaft, will be visible.
Good luck
There is a small amount of play in the nylon gear in the photo but none of them seem damaged. The small nylon wheel in the fine focus shaft looks ok too. Some dried grease on one of the metal gears but both metal gears turn ok when the nylon wheel is turned.

The silver main focus shaft is still not revolving smoothly with the fine focus shaft removed.

I have acetone but the Losoid 1160C seems to be hard to find in the UK. Is there something more easily available I could use? I have Lithium or silicone grease in a spray can.

Image

PrecisionInstruments
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Re: BH-2 Focus adjustment question

#16 Post by PrecisionInstruments » Wed Jan 15, 2020 1:00 am

I would not suggest to use lubricant from a spray can, the propellant can cause damage to the metal parts. I have only ever used Olympus and Leica original lubricant so am unsure of what else can be used which is readily available, maybe Black molykote?
With the gear box in place, and the fine focus shaft removed, the stage should fall under its own weight, and you should see those planetary gears spin. You can lift the stage slowly by hand, also seeing this planetary gears spin.
It’s possible that the lubricant in the ball bearings in fig 58 & 59 have become dry. This would be too far in the system to pull apart by someone without experience.
If you were in Perth, Australia I would rebuild the system completely for a nice cold carton of Peroni!!
I have a headache, For which the future’s made

Hobbyst46
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Re: BH-2 Focus adjustment question

#17 Post by Hobbyst46 » Wed Jan 15, 2020 11:17 am

May I add a general note here: I would not use acetone on nylon parts. Acetone is too powerful against many plastics. Grease usually softens and/or dissolves in less agresive liquids: Petroleum ether ("white benzin", "white gasoline", "ligroin" etc), cigarette lighter fluid, octane, even thin machine oil.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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