Reichert Diastar 420 coarse focus problem

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jjcook
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Reichert Diastar 420 coarse focus problem

#1 Post by jjcook » Fri Sep 18, 2020 2:56 am

I recently picked up a Diastar at auction (its returnable if necessary) and upon initial inspection have found the coarse focus to have major problems, perhaps because it was shipped with the full nosepiece in place and not secured.
  • when reversing directions it takes about a quarter turn before it engages the mechanism
  • very rough and gritty motion with lots of intermittent slip and jumps
  • ... and more
I've attempted to disassemble the focus mechanism to identify the problem but I've gotten stuck very early: I have removed both fine focus knobs and removed the set screw in each coarse focus knob which allowed me to remove the fine focus shaft, but at this point its not clear how to continue disassembly. Any experts with advice?

I did look through the patent diagram of this focus mechanism posted viewtopic.php?t=10113 but I'm not seeing much that is helpful toward disassembly...
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- Jeff

hans
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Re: Reichert Diastar 420 coarse focus problem

#2 Post by hans » Fri Sep 18, 2020 3:53 am

jjcook wrote:
Fri Sep 18, 2020 2:56 am
...removed the set screw in each coarse focus knob which allowed me to remove the fine focus shaft...
On my 410s there are two set screws in each knob, 180 degrees apart on the right side and 90 degrees apart on the left. I don't think the set screws in the coarse focus knobs should have anything to do with removing the fine focus shaft. If the fine focus shaft really wouldn't come out until you removed the coarse knob set screws, that seems strange, like something was assembled incorrectly or over-tightened or something?

hans
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Re: Reichert Diastar 420 coarse focus problem

#3 Post by hans » Fri Sep 18, 2020 4:02 am

It may not be necessary to remove those knobs to get a good idea what is going on, though. Have you tried taking the illumination stuff off the back? If the basic frame casting is similar to the 410 you can see the focus cam pretty well through back.

jjcook
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Re: Reichert Diastar 420 coarse focus problem

#4 Post by jjcook » Fri Sep 18, 2020 4:33 am

hans wrote:
Fri Sep 18, 2020 3:53 am
On my 410s there are two set screws in each knob, 180 degrees apart on the right side and 90 degrees apart on the left. I don't think the set screws in the coarse focus knobs should have anything to do with removing the fine focus shaft. If the fine focus shaft really wouldn't come out until you removed the coarse knob set screws, that seems strange, like something was assembled incorrectly or over-tightened or something?
Wow -- great catch! I wasn't paying close enough attention to notice the second set screw on each knob (isn't that embarrassing!). Okay each knob has come off ... stopped there just to provide this update.


Regarding looking through the illumination system, I haven't yet figured out how to remove that and will hold off for now -- I have the top and bottom off and am able to see the focus cam although perhaps not from the best perspective.
- Jeff

PeteM
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Re: Reichert Diastar 420 coarse focus problem

#5 Post by PeteM » Fri Sep 18, 2020 4:57 am

Recollection is that you can take the lid off the top (screws under plugs) and get a view down into the focusing mechanism and see if the plastic cam down inside is broken. That could be your problem. The upper arm of the scope (its retract mechanism) rests on that plastic cam. It doesn't like to be dropped.

I repaired one by pulling the whole thing apart, doing an epoxy (JB Weld) build up for a repair on the cam. This involved taping on the outer cam profile, filling the hollow of the cam with epoxy, and smoothing it. I was also able to adjust the stage height so a still-good part of the cam operated in the focusing region.

If the cam is busted and there's no problem returning the scope, I'd say it's not worth the effort to repair it unless you got or get an exceptional deal.

Otherwise a pretty nice scope - and usually a bit cheaper that the big four equivalents with 100 watt lamps.

hans
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Re: Reichert Diastar 420 coarse focus problem

#6 Post by hans » Fri Sep 18, 2020 5:06 am

In your photo of the right knob had you already removed a little plate and two gears? If not you are missing part of the fine focus gear train and I think that would explain (in combination with some stiff bearings, maybe) the quarter-turn backlash in the coarse focus you described. Was the fine focus doing anything before you started disassembly?

hans
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Re: Reichert Diastar 420 coarse focus problem

#7 Post by hans » Fri Sep 18, 2020 5:24 am

PeteM wrote:
Fri Sep 18, 2020 4:57 am
...I'd say it's not worth the effort to repair it unless you got or get an exceptional deal.
Look at sold listings... if that is jj's and the optics are ok, seems like a very good price for a Diastar with trinocular head if it can be fixed with parts from another cheap 410?

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Re: Reichert Diastar 420 coarse focus problem

#8 Post by jjcook » Fri Sep 18, 2020 6:05 am

Ok, got the kids to bed -- back to work!

Once I removed the next layer of hardware on the right side I exposed the final assembly of the focus cam with a single gear that ties it to the rest of the coarse focus knob assembly. I played with moving this (and thus the internal upper arm) and it was quite jittery. At first I presumed the issue might be the cam rubbing up against the bearing/guide assembly on the bottom of the arm, but it didn't look like there was any room to back off the cam laterally.

So out came the focus cam assembly, photos below:
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Once I got it down to just the focus cam assembly, I found that it was very tough and jittery to turn. My current theory is that if I disassemble, clean, and grease this focus cam assembly that the gritty coarse focus will be solved. What should I use to clean off the old grease and what new grease should I apply?

This doesn't answer the question regarding the coarse quarter-turn backlash(?) I presume...
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Re: Reichert Diastar 420 coarse focus problem

#9 Post by jjcook » Fri Sep 18, 2020 6:11 am

What is the purpose of the two blue nubs on the focus cam assembly? There is a matching blue nub on the coarse focus knob assembly (see photo below but on the underside) -- and when disassembling I did not take note of how the single nub aligned with the two other nubs, I presume it was in-between the two (which seems to correspond to the quarter turn slop when changing directions on the coarse focus, so maybe intentional?).

Also hans my "little plate and two gears" was just a little plate and one gear (the other hole isn't drilled out enough for a second gear) -- perhaps its how the blue Diastar version without the focus lock was built.
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Last edited by jjcook on Fri Sep 18, 2020 6:30 am, edited 1 time in total.
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PeteM
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Re: Reichert Diastar 420 coarse focus problem

#10 Post by PeteM » Fri Sep 18, 2020 6:20 am

The good news is that your cam isn't broken. You're likely right that it's hardened grease.

I find a spout top can of lighter fluid a good solution for applying small amounts of a not-too-hazardous solvent. Loose the old stuff, pick out the hardened grease from racks and gears with a toothpick and stiff bristle brush. Once scrupulously clean, apply new grease where it's called for.

When you track the problem down, this will be a great thread for future owners.

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Re: Reichert Diastar 420 coarse focus problem

#11 Post by jjcook » Fri Sep 18, 2020 6:26 am

I also noted that moving the internal arm free of the focus cam that the two ball bearing assemblies guiding the internal arm are also very gritty and jittery. These are deep in the machine and will definitely require removing the power electronics to access them. This is becoming a project!

It looks like I’ll need to remove the screw marked in red to loosen the collar — I’m uncertain about how to repair this part without further research. Edit: it’s a Thomson Super 8 OPN linear ball bushing, I’ll have to read on its failure modes else replace one or both of them for maybe $50
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You're right hans that was the listing I grabbed as soon as it was listed since these come up so rarely (the one benefit of getting up every 1.5 hours to take the 10 week old puppy outside in the early hours of the morning I guess) -- $186 shipped. :D

Assuming that the coarse focus issue is on track, I now need to finish looking over the rest of the unit in the next few days to decide if there are any other deal breakers... the nosepiece seems to need work too as it doesn't turn smoothly as if it was tightened closed a little too much, and unfortunately the trinocular head has a little bit of clouding that I presume is the beginning of delamination (or fungus?) but its out of the field of view I think and is not as bad as the dual head AO 110 that I recently acquired.
Last edited by jjcook on Fri Sep 18, 2020 7:56 am, edited 1 time in total.
- Jeff

hans
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Re: Reichert Diastar 420 coarse focus problem

#12 Post by hans » Fri Sep 18, 2020 7:16 am

jjcook wrote:
Fri Sep 18, 2020 6:05 am
This doesn't answer the question regarding the coarse quarter-turn backlash(?) I presume...
jjcook wrote:
Fri Sep 18, 2020 6:26 am
I also noted that moving the internal arm free of the focus cam that the two ball bearing assemblies guiding the internal arm are also very gritty and jittery.
Does the nosepiece fall down under its own weight? If not that could also explain the 1/4 turn backlash, if it needs the pin stop opposite the follower bearing riding on the inside of the cam to pull it down. In addition to the two big linear bearings on the rod there are two small bearing rollers on the left/right sides of the nosepiece in the front to keep it centered. Roughness of the nosepiece motion with cam removed in my stands was caused by those rollers being dirty, not by the big linear bearings.
jjcook wrote:
Fri Sep 18, 2020 6:11 am
What is the purpose of the two blue nubs on the focus cam assembly? There is a matching blue nub on the coarse focus knob assembly (see photo below but on the underside) -- and when disassembling I did not take note of how the single nub aligned with the two other nubs, I presume it was in-between the two (which seems to correspond to the quarter turn slop when changing directions on the coarse focus, so maybe intentional?).
I believe the three pins together serve to limit the rotation of the coarse focus knob relative to the frame to a little less than one full turn, so that the cam/follower are not the limit.
jjcook wrote:
Fri Sep 18, 2020 6:11 am
Also hans my "little plate and two gears" was just a little plate and one gear (the other hole isn't drilled out enough for a second gear) -- perhaps its how the blue Diastar version without the focus lock was built.
Ah, yeah, my blue-top 410 only had one gear, black-top had two, so it seems like the spring-loaded parallel gear train was left out of the blue-top revision.
jjcook wrote:
Fri Sep 18, 2020 6:26 am
You're right hans that was the listing I grabbed as soon as it was listed since these come up so rarely (the one benefit of getting up every 1.5 hours to take the 10 week old puppy outside in the early hours of the morning I guess) -- $186 shipped.
I would have been very tempted to buy it if I had seen it, probably best I didn't...
jjcook wrote:
Fri Sep 18, 2020 6:26 am
...unfortunately the trinocular head has a little bit of clouding that I presume is the beginning of delamination (or fungus?) but its out of the field of view I think...
If you can be sure it is in the binocular section (one of mine has a splitter that is clouded internally) and camera path is ok, I have not found any difference optically in the binocular section between the standard and trinocular heads, and they can definitely be swapped mechanically.

apochronaut
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Re: Reichert Diastar 420 coarse focus problem

#13 Post by apochronaut » Fri Sep 18, 2020 12:19 pm

You have to be careful with the colours. The earliest versions had a black arm cap and then Leica branded ones at the end too.

hans
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Re: Reichert Diastar 420 coarse focus problem

#14 Post by hans » Fri Sep 18, 2020 4:56 pm

apochronaut wrote:
Fri Sep 18, 2020 12:19 pm
You have to be careful with the colours. The earliest versions had a black arm cap and then Leica branded ones at the end too.
Good to know, have you noticed any significant mechanical differences other than the removal of the focus lock thing and leaving out the spring-loaded fine focus gear train?

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Re: Reichert Diastar 420 coarse focus problem

#15 Post by jjcook » Tue Sep 22, 2020 7:25 am

Made a little progress (and a step backwards) tonight but will post photos and details tomorrow...

Once I start reassembling, what grease/oils should I use for the coarse focus? fine focus? nose turret? stage? condenser? (and internal focus arm on Tomson Super 8 linear bearings which is quite noisy?) From my not-so-brief perusal around here, I see the following are often recommended in general: Nye 179 light oil, Nye 362HB, Nyogel 767A, Molykote 111.
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Re: Reichert Diastar 420 coarse focus problem

#16 Post by hans » Wed Sep 23, 2020 1:49 am

I am also curious about silicone greases like Molykote 111 you mention. I have a tube of it for underwater-mateable electrical connectors and it does seem like it would give a nice feel on mechanisms. I have not tried it yet though because I remember seeing some general recommendations against using silicone lubricants near optics -- concern it was prone to migrate or evaporate/deposit residue on nearby surfaces. Maybe less of a worry if used somewhere like the stage or focus drive.

So far I have just been using some Starrett "tool and instrument" oil for the ball bearings (on mine they are all shielded bearings and would be difficult to grease) and some MG Chemicals white lithium grease for everything else because I had them around and have not had the patience to research and track down a good place to buy small quantities of the recommended Nye lubricants.

PeteM
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Re: Reichert Diastar 420 coarse focus problem

#17 Post by PeteM » Wed Sep 23, 2020 4:54 am

A plus with some of the silicon greases is that they are very stable and not likely to oxidize over time; especially ones certified for things like vacuum duty.

You would want to thoroughly clean old greases out thoroughly before switching, though, to avoid possible incompatibilities.

apochronaut
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Re: Reichert Diastar 420 coarse focus problem

#18 Post by apochronaut » Wed Sep 23, 2020 12:58 pm

hans wrote:
Wed Sep 23, 2020 1:49 am
I am also curious about silicone greases like Molykote 111 you mention. I have a tube of it for underwater-mateable electrical connectors and it does seem like it would give a nice feel on mechanisms. I have not tried it yet though because I remember seeing some general recommendations against using silicone lubricants near optics -- concern it was prone to migrate or evaporate/deposit residue on nearby surfaces. Maybe less of a worry if used somewhere like the stage or focus drive.

So far I have just been using some Starrett "tool and instrument" oil for the ball bearings (on mine they are all shielded bearings and would be difficult to grease) and some MG Chemicals white lithium grease for everything else because I had them around and have not had the patience to research and track down a good place to buy small quantities of the recommended Nye lubricants.
Nye's small quantity distributor ( anything under 500.00) is TAI lubricants. Many microscope components require a damping grease, which has clutching characteristics along with lubricating characteristics. For this reason, for certain applications in a microscope, very slippery lubricants are to be avoided and in some cases a dry lubricant such as graphite powder is best. I came across a lubricant list from AO, which listed the suppliers for their lubricants. There were a great many, somewhere around 12 or so. It seems that to get the correct action from all the parts, you need quite a few viscosities and sometimes they need to be blended.

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Re: Reichert Diastar 420 coarse focus problem

#19 Post by hans » Wed Sep 23, 2020 8:31 pm

PeteM wrote:
Wed Sep 23, 2020 4:54 am
A plus with some of the silicon greases...
Any opinion on the concerns regarding silicone grease near optics that seem to be repeated various places around the web? Seem to me like it would probably be fine except maybe something very close to optics like a nosepiece bearing or eye tube focuser. Just a quick search "silicone grease microscope" brings up this presentation for example which says, "Do not use silicone grease because it creeps and has an affinity for glass!" I remember seeing similar warnings elsewhere but don't remember how reputable the sources were.
apochronaut wrote:
Wed Sep 23, 2020 12:58 pm
Nye's small quantity distributor ( anything under 500.00) is TAI lubricants.
Looks like still $60-70 minimum for the smallest tubes, though? I think I remember reading earlier that there used to be an assortment of small quantities several types available for a reasonable price, but it was discontinued?

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Re: Reichert Diastar 420 coarse focus problem

#20 Post by apochronaut » Wed Sep 23, 2020 9:28 pm

There used to be a hobby kit, with 1 tube of damping grease and 1 vial each of a light viscosity and heavy viscosity oil. Was originally quite cheap at around 20.00, maybe 25. It was discontinued. I called TAI and they had a few left, about a year ago. 39.00 I think it was.

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Re: Reichert Diastar 420 coarse focus problem

#21 Post by hans » Wed Sep 23, 2020 9:56 pm

apochronaut wrote:
Wed Sep 23, 2020 12:58 pm
Many microscope components require a damping grease, which has clutching characteristics along with lubricating characteristics.
If someone was going to buy just one type of Nye grease which would you recommend as most useful for damping purposes, with an emphasis on stages? Stages are what I have been having the most difficulty getting a good feel on, and where I was thinking of trying some thicker silicone grease. With the focus mechanism on the 410s the commodity oil/grease I have been using seems fine and I don't see much room or need for improvement. And the rest of the stuff (condenser height, eye tube focus, nosepiece, Siedentopf joint, etc.) is not subject to such frequent and precise use as the stage and focus, so not as much incentive to use exactly the right lubricant.

I tried some thick, sticky, black molybdenum/graphite automotive bearing grease on the stage at one point out of curiousity. It actually gave a better, more controllable feel than the lighter white lithium grease, but there was a slight graininess to it, maybe the graphite particles? Ultimately I couldn't stand the stench of it indoors and went back to the while lithium.

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Re: Reichert Diastar 420 coarse focus problem

#22 Post by PeteM » Wed Sep 23, 2020 10:16 pm

hans wrote:
Wed Sep 23, 2020 8:31 pm
PeteM wrote:
Wed Sep 23, 2020 4:54 am
A plus with some of the silicon greases...
Any opinion on the concerns regarding silicone grease near optics that seem to be repeated various places around the web . . .
Hans, I’m not an expert in greases, so take this with a grain of salt:

1) There are oil based, synthetic oil base, and silicone (a specific synthetic) oil-based greases. The helicoid grease I’ve been using is a fairly stable synthetic with tiny PTFE (Teflon) particles and an old standby (lithium) as thickeners. It has worked OK, once the old gummed up grease has been removed: https://www.amazon.com/MicroLubrol-Heli ... B00D0HOLO6

I’ve also used the Nye product - also OK but mine (would have to check the #) a bit too much damping IMO. It’s probably an NLGI #2 rather than the lighter NLGI #1 consistency. Note on the following link that many Nye damping greases are based on synthetic oils and thickened by silica:

https://shop.newgatesimms.com/damping-grease/

Many of the Molykote products are also PAO synthetics.

“Super Lube” is another synthetic grease with tiny PTFE particles – this one a medium thick NLGI grade 2 grease.

2) One of the pluses of many synthetic and most silicone greases is their ability to resist outgassing and high temperatures. This should also lead to longer stability and less chance they might run (and migrate) from something like the heat of a 100 watt illuminator? Silicone greases do have low surface tension so they’re likely to spread over the surface they’re lubed with. I don’t see them “jumping” to adjacent glass, though.

3) I have heard (but can’t verify specific instances) of incompatibilities of various mineral and synthetic bases and thickeners. Hence the advice to thoroughly clean off the old stuff. I do know that gear oils with EP additives (to handle pressure) like sulfur will attack brass gears and slides.

4) Silicone greases do stick pretty well to glass if you screw up. However, an added factor is that they aren’t soluble in alcohol (the main solvent besides water in many lens cleaners), so that may be the source of some concern about cleaning them off should they get on glass. They are soluble in solvents like mineral spirits, toluene, hexane, petroleum ether, etc. etc. So they should clean off with the right solvent if there’s a mistake and a smear?

Don’t know about the effects, if any, of various greases and oils on various coatings. The fatty oils from our fingertips seem to come off easily enough. I’m personally more worried about greases and oils dripping, outgassing, or oxidizing over time than screwing up and smearing them on a lens, though that is of course a risk.

5) Silicone greases are often used as a water-proof lubes for rubber parts (o-rings etc.) – even with underwater cameras -- but aren’t good with silicone rubbers.

6) All of which suggest to me that synthetic oil based greases are likely dominant today in optics – but silicone synthetics are to be used with some caution.

7) All that said, I’m amazed how well some fifty year old Japanese microscopes (Tiyoda an example) sometimes still function with old oil-based greases – apparently with little or no maintenance over the years. I came across a couple small tubes of two greases – still good decades after the company ceased US business.

The link you posted does seem to have a lot of good info. However, some of the advice such as never trying to repair an objective or condenser would have left me short of several now-repaired objectives and condensers.

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Re: Reichert Diastar 420 coarse focus problem

#23 Post by PeteM » Wed Sep 23, 2020 10:23 pm

hans wrote:
Wed Sep 23, 2020 9:56 pm
apochronaut wrote:
Wed Sep 23, 2020 12:58 pm
Many microscope components require a damping grease, which has clutching characteristics along with lubricating characteristics.
If someone was going to buy just one type of Nye grease which would you recommend as most useful for damping purposes, with an emphasis on stages? Stages are what I have been having the most difficulty getting a good feel on, and where I was thinking of trying some thicker silicone grease. . . .
A couple points on stages.

First some older scopes have brass dovetails and newer ones typically have ball bearings running against hardened rails or wires. I wouldn't use a heavy damping grease with either. There are usually gib adjustments to tighten or loosen the rails and get an evenly-distributed slight drag across the entire range of movement.

My own experience is that the "feel" of stages is then very dependent upon adjustment. Once you get the dovetail or ball bearing slides to move fairly with slight pressure while normally greased, then the adjustment of the racks against the pinions and the X and Y knobs against their Belleville (disk spring) washers controls the final feel.

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Re: Reichert Diastar 420 coarse focus problem

#24 Post by PeteM » Wed Sep 23, 2020 10:58 pm

Just to add to the what-grease discussion - I just came across two articles. One by a traditional hydrocarbon based grease maker trashing silicone greases for messing up surfaces that had to be painted, creeping, etc. This one by a silicon base grease maker calling much of that a myth:

https://www.ecllube.com/resources-for-e ... Grease.pdf

There's also a link to an engineering lubricant guide which discusses various thickeners and compatibility issues. This probably is of only theoretical interest, since we rarely know what thickener is in the old hardened grease we're trying to remove. What's not theoretical is the risk of incompatibilities.

As for what to get - I use a plain light mineral oil where appropriate and sometimes to loosen up an old stiff petroleum-based grease for another year or two. A bit of heat can help get things started. Starrett instrument oil is an example of a relatively pure light oil.

Then synthetic (but not silicone) greases in NLGI 1 & 2 viscosities and a Helicoid NLGI 1 damping grease. Also have a Nye heavy damping grease, but don't use it much for optics - seems a little too stiff to me.

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Re: Reichert Diastar 420 coarse focus problem

#25 Post by hans » Thu Sep 24, 2020 3:57 am

Thanks for all the info, Pete. That helicoid grease on Amazon sounds promising, and much less of an investment than the Nye stuff. I went the found the silicone Molykote I have for underwater connectors (which are using NBR for seawater compatibility) and it is 55 not the 111 Jeff mentioned. One thing that concerns me about it is that is does seem to separate over time. I use it infrequently and there is always a little silicone oil accumulated in the cap when I remove it. Not sure if that is a general characteristic of silicone greases, or something specific to the 55. I also have a jar of "3M car care silicon paste dielectric grease" which I have not noticed separating, but I suspect is too thick/viscous. Glad you mentioned "Super Lube", when I looked it up and saw photo I remembered I had some in my bike tool box (recommended for the suspension bushings) which I had forgotten about when I went rounding up all my greases a few months ago.

Regarding stage adjustment, from my experimentation so far the ball bearing ways themselves on the 400 series seem to be extremely slippery with low damping no matter what lubricant or preload force, up to the maximum I can apply by hand. Seems like damping/drag needs to come from the rack/pinion or control knobs with their friction pins. I think the main problem I have now with the white lithium grease is stiction between the plastic (nylon or polyethylene, maybe?) pins and brass shafts in the controls when they are tensioned enough to give reasonable drag. I wonder if the stiction problem could also be related to contact area? The pins on mine are well-worn to match the shafts giving very large contact area. Perhaps they were originally flat or rounded with much smaller contact area?
PeteM wrote:
Wed Sep 23, 2020 10:16 pm
The link you posted does seem to have a lot of good info. However, some of the advice such as never trying to repair an objective or condenser would have left me short of several now-repaired objectives and condensers.
Agreed, I hadn't actually looked through the presentation, just linked to it as an example of the sort of vague, unsourced warning against silicone grease I remembered seeing frequently.

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Re: Reichert Diastar 420 coarse focus problem

#26 Post by jjcook » Fri Sep 25, 2020 8:53 pm

Recall that this coarse focus mechanism was very rough and jittery -- as it turned out it was just due to hardened grease. I disassembled and cleaned it with naphtha, but during disassembly (removing bearings) I messed up one of the two IJK 6901Z bearings (Z for single metal shield) so I ordered two replacement bearings of the same size but self lubricated with rubber shields on both sides (as that is what I could easily find inexpensively for this initial fix to validate no other issues with the focus). I have temporarily reassembled it just applying light oil (Nye 179) to the inner surface of the bearings (along the shaft) and also along the shaft this mechanism rides. I'm guessing I should have used grease here but it hasn't shown up yet and I'm still not clear on which kind to use for this. Overall when cleaning out this mechanism there was very little grease (which was all dry), a far cry from what I see in Carl's BH2 repair documents. Maybe the original open sided bearings are where a bulk of damping grease is supposed to be applied? Once I finish reassembly tonight I'll see what it feels like, but presently turning the coarse focus gear by hand the nose movement is smooth but very slick. I will still need to grease the fine focus too, I guess just the gear shafts mounting points with a little 767A? I'm still lost when it comes to figuring out what needs to be greased particularly for the correct clutching, so I'll experiment...

In the third photo you can also see the focus arm that did not move smoothly along the linear bearings (once disconnected from the focus cam), which I also cleaned and applied a small amount of light oil and worked it into the linear bearings which smoothed it out and reduced the grinding sound from the linear bearings (which were very clean and dry to start with):

Disassembled but not yet cleaned:
IMG_9049.jpg
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The infamous bearing:
IMG_9050.jpg
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After disassembly. Note the open (on inner side) bearings that are separated by a thin spacer):
IMG_9055.jpg
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Cleaned and reassembled with just a touch of light oil:
IMG_9079.jpg
IMG_9079.jpg (72.58 KiB) Viewed 412 times
Installed: (any reason to grease the wave washer? currently it just moves with the inner bearing surface without slipping)
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IMG_9080.jpg (103.4 KiB) Viewed 406 times
- Jeff

hans
Posts: 342
Joined: Thu May 28, 2020 11:10 pm
Location: Southern California

Re: Reichert Diastar 420 coarse focus problem

#27 Post by hans » Fri Sep 25, 2020 11:02 pm

Sounds like good progress. Did you disassemble the focus knob on the left side at all? Friction on the coarse focus is set by clamping force applied by a Belleville washer, not labelled, but shown sandwiched between two flat washers between the parts labelled 58 and 138 in the patent drawing. Note that some parts on the inside near where the label 74 points, which are what transmit the clamping force to the opposite side of the plate 58, are omitted from the drawing. With everything clean and lubricated damping grease alone will not keep the focus arm from falling under it's own weight while backdriving the cam, I am pretty sure, and friction needs to be set by tensioning that Belleville washer appropriately.

hans
Posts: 342
Joined: Thu May 28, 2020 11:10 pm
Location: Southern California

Re: Reichert Diastar 420 coarse focus problem

#28 Post by hans » Fri Sep 25, 2020 11:08 pm

Also, since the coarse friction is set on the left side, you will not have any friction on the cam until you reinstall the knob and fine focus gear train on the right.

jjcook
Posts: 30
Joined: Wed Jul 29, 2020 4:23 am
Location: Portland, OR, USA

Re: Reichert Diastar 420 coarse focus problem

#29 Post by jjcook » Fri Sep 25, 2020 11:33 pm

Yes, I fully removed the left hand side focus down to removing 58 that supports the coarse focus shaft. Good to know the tension will come back when I install the left/right side -- as I was hoping :). Do I need to grease any of these tension washers as I reassemble both sides?

Actually I noticed upon reassembly of 56 & 58 (maybe it was this way originally), I don't have the shaft lined up coaxially with the coarse focus cam side -- as there is some wobble to the shaft visible where the fine focus mechanisms on the right side will mount, so I'll need to play with this first.
- Jeff

jjcook
Posts: 30
Joined: Wed Jul 29, 2020 4:23 am
Location: Portland, OR, USA

Re: Reichert Diastar 420 coarse focus problem

#30 Post by jjcook » Fri Sep 25, 2020 11:40 pm

And since I removed the focus arm I've realized that I'll definitely need to re-set the "auto-focus" range. Is the AO110 service manual the best approximate description of this process?

Edit: Restated, do I just use the procedure in the Microstar IV manual to set auto-focus, or do I need a more involved procedure to get the coarse/fine focus knob initialized in the correct location?
- Jeff

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