Help Needed with Stuck Field Iris

[JGardner]

I've just acquired a Leitz Orthoplan from an eBay seller and the field iris built into the base is frozen in the fully open position. The thumb wheel meant to control the iris won't budge. From reading the instruction manual, I'm pretty confident there's no lock for the iris control, so there's nothing that should be preventing me from closing it down.

How should I go about freeing the iris? I'm assuming that using a tool to apply more force to the control wheel is probably not the best approach? Perhaps it's stuck because lubricant has dried out and turned into glue? In that case, would it be possible to squirt some penetrating oil or solvent into the iris mechanism to dissolve the dried lubricant?

Another possibility is to apply a heat gun to the iris mechanism and heat it up in an attempt to melt any solidified lube--is this a reasonable thing to try?

The iris mechanism is integrated into the base of the stand and appears to be part of a removable module that includes the 45-degree first surface mirror that reflects light up to the condenser. Should I try to remove this module so I have better access to the iris mechanism? Does it go back together again easily?

I'm open to any and all advice that might help me get the field iris operational again.

Jerry

The photo below shows the thumb wheel used to control the iris:

[MikeA]

Hello,

Reading this and your other post it appears there are a number of major problems with that Orthoplan;

The mirror is loose from its mount in the base.

The field iris is frozen

The coarse focus is stiff, if not frozen

The optics are dirty if not missing

The condenser centering screws are not functioning properly

And I expect there are several other problems, e.g. how does the interpupillary distance adjustment on the headpiece work? I expect that it 'frozen' as well.

How clean is the optic train in the headpiece?

In truth, if you have the ability to return this scope for a full refund I would suggest that might be the best route, as it was, I believe, sold as fully functioning and it is certainly not. PayPal/eBay will assist in a return/refund.

In the event you want to keep it, you should at a minimum require a refund of a majority of your payment, and I would suggest you only do that as a last resort.

All the things that are problems can be repaired in all likelihood, but they do require some knowledge/equipment that might be an additional expense, and for what you paid you have a right to expect a microscope in not only good working condition, but in excellent condition and certainly more complete.

In the interim, whatever you do, do NOT force the field diaphragm via excessive force - or any other part; that may do permanent damage.

You are likely correct in your surmise it is probably locked due to old lubricant or whatever that has polymerized. A reasonable application of hot air from a blow dryer while attempting to move the dial may break it loose, and then working it for a bit will help. I do not recommend use of penetrating oil.

The correct method is to remove the mirror mount which also mounts the diaphragm, then removing the diaphragm from the base and 'washing' it in a series of solvents to remove entirely any old lubricant/dust/rust/whatever. The diaphragm is designed to operate 'dry', i.e. no lubricant.

If you want to try this, you will first need to remove the getting into collector lens control knob by removing the screw in the top center, then using a small gear puller to pull the knob off the axle. Once this is done, the entire mirror/diaphragm mechanism may be removed by loosening the four machine screws that hold it in (the two smaller ones hold the diaphragm mechanism to the base.)

Once you have the diaphragm free from the base, I would suggest you soak it in a few baths of heptane if available, if not, you can use/try whatever hydrocarbon solvent you are comfortable with, just be mindful that ROH has little to no solvent effect here, and heptane/benzene/xylene et al are serious health concerns. Unfortunately the solvency of most material is inversely proportional to health safety.

After multiple baths (and actuation) you should experience a freeing of the mechanism, and note quite a bit of rust coming off - this is normal. When the no further rust is evident and the diaphragm actuates freely when dry, it can be reassembled.

As you probably know already, the mirror is a first surface mirror and should not be touched - I clean them using a material "First Contact Polymer" available on line. Expensive, but when used with care does a great job and lasts a long time.

Be mindful, of the repairs/maintenance that are required, this is the simplest of the things that need doing.

If you would like to contact me via PM that would be fine.

I certainly do not wish to 'rain on your parade' as regards your new microscope, but I think I need to be honest with you.

[Hobbyst46]

@JGardner
MikeA's advice is in my opinion extremely sensible. An extremely dirty microscope is a long neglected microscope.

[JGardner]

Mike,

Thanks for your comments. My replies below...

The mirror is loose from its mount in the base.

This may have been caused by shipping the microscope. As I haven't looked closely at how the mirror is attached to the stand, I'm still not sure how to re-secure it--do you know how it's held in place?

The field iris is frozen

Yep, this is the biggest remaining issue with this microscope.

The coarse focus is stiff, if not frozen

The coarse focus is not frozen. It's stiffer than the fine focus, but not significantly more so. It may be normal, but I have no way of judging as this is the first Leitz microscope I've ever worked with.

The optics are dirty if not missing

The optics are dirty as if this microscope was stored on a shelf for years with no dust cover and should be as good as new with a good cleaning. As far as I know, none of the optics are missing. The K4 lens mentioned in my other thread is, I believe, an optional item and not a standard part of the condenser. So far I haven't noticed any ill effects of not having one.

The condenser centering screws are not functioning properly

As far as I can tell, this is correct. I'm not sure how these screws work... There are two arranged 45 degrees apart on one side of the condenser. I can see how tightening one or both of them would move the internals of the condenser in that direction, and I assume there is something inside the condenser that moves the parts in the other direction when the screw(s) are loosened. I presume there are springs of some sort to accomplish this, but I don't know. If that's the case, it would seem that either the springs have lost their springiness or a lubricant has dried up and is preventing the springs from doing their job. Any information regarding this would be most helpful.

And I expect there are several other problems, e.g. how does the interpupillary distance adjustment on the headpiece work? I expect that it 'frozen' as well.

It works very well. It's not frozen and the movement is not stiff.

How clean is the optic train in the headpiece?

Spotless. The only dirt on the optics is on the optics directly exposed. For example, the eye lenses of the eyepieces are dirty, but pull them out and the back lenses are clean with no dirt or dust.

In truth, if you have the ability to return this scope for a full refund I would suggest that might be the best route, as it was, I believe, sold as fully functioning and it is certainly not. PayPal/eBay will assist in a return/refund.

At this point, I don't think I'll be returning this microscope. I knew going in that this scope was at least 35 years old and perhaps older and wouldn't be like a new scope fresh from the factory. There were a few things about the description on eBay that do seem problematical given what I've found. The statement "was removed from a working lab and is in good condition" doesn't quite ring true unless whoever used this scope in the lab never bothered with the field iris and just left it open. I wonder also about the missing power supply for the lamp house--did this get lost when the scope was acquired by the eBay seller? One wonders how the scope was used without the power supply. The other questionable statement in the eBay listing, "all control knobs function correctly", certainly doesn't apply to the field iris control and I strongly doubt that the iris froze up as a result of shipping.

In the event you want to keep it, you should at a minimum require a refund of a majority of your payment, and I would suggest you only do that as a last resort.

I think that's overstating the case. Sure, there are some issues (frozen iris and problems centering the condenser), but I don't think that justifies a refund of >50% of what I paid.

All the things that are problems can be repaired in all likelihood, but they do require some knowledge/equipment that might be an additional expense, and for what you paid you have a right to expect a microscope in not only good working condition, but in excellent condition and certainly more complete.

As I'm not familiar with Orthoplans and the used microscope market in general, I don't know if $975 was too much to pay for a scope in this condition. Perhaps it was and perhaps I could have gotten a scope in better condition for less money. I did search out other listings on eBay and other sites and most were in the $1500 to $3000 range.

In the interim, whatever you do, do NOT force the field diaphragm via excessive force - or any other part; that may do permanent damage.

Good advice. I don't plan to, especially since I don't even know which direction moving the control wheel closes down the iris.

The correct method is to remove the mirror mount which also mounts the diaphragm, then removing the diaphragm from the base and 'washing' it in a series of solvents to remove entirely any old lubricant/dust/rust/whatever. The diaphragm is designed to operate 'dry', i.e. no lubricant.

If you want to try this, you will first need to remove the getting into collector lens control knob by removing the screw in the top center, then using a small gear puller to pull the knob off the axle. Once this is done, the entire mirror/diaphragm mechanism may be removed by loosening the four machine screws that hold it in (the two smaller ones hold the diaphragm mechanism to the base.)

Once you have the diaphragm free from the base, I would suggest you soak it in a few baths of heptane if available, if not, you can use/try whatever hydrocarbon solvent you are comfortable with, just be mindful that ROH has little to no solvent effect here, and heptane/benzene/xylene et al are serious health concerns. Unfortunately the solvency of most material is inversely proportional to health safety.

After multiple baths (and actuation) you should experience a freeing of the mechanism, and note quite a bit of rust coming off - this is normal. When the no further rust is evident and the diaphragm actuates freely when dry, it can be reassembled.

Thanks for the detailed description. Sounds straightforward. n-heptane might be a little hard to find locally, so I'll probably try petroleum naphtha in the form of Coleman lantern fuel, which is readily available locally. As a former chemist, I'm well-versed in the safety aspects of working with organic solvents.

As you probably know already, the mirror is a first surface mirror and should not be touched - I clean them using a material "First Contact Polymer" available on line. Expensive, but when used with care does a great job and lasts a long time.

I'll check out First Contact Polymer. I do have experience cleaning reflector telescope mirrors, which are also first surface mirrors, so I do have that experience to lean on.

I certainly do not wish to 'rain on your parade' as regards your new microscope, but I think I need to be honest with you.

Thanks. I knew going in that this was a used, decades old, microscope that probably had issues that would need to be resolved. None seem like something I'd totally write off this scope for, however.

[MikeA]

Hello!

Hoping to address your comments in order:

The mirror is glued (epoxy or the equivalent from 60 - 70 years ago) to a metal pedestal that is attached to the base with machine screws. In many years of shipping/receiving Orthoplans I have never seen a mirror come loose in shipment. In the event yours is damaged beyond repair, I have a spare in my parts that I am sure we can come to an amicable arrangement.

If the mirror itself has come off the pedestal, it should be simply re-glued, making sure the old glue is removed first. Obviously if the pedestal itself is loose, the more-to-be-hoped for situation, reattaching it to the base is all that is required, although there is the possibility, if not probability, the alignment will be effected, and that would be problematic, but one must first ascertain the nature of the problem.

Yes, n-heptane can be difficult to source but it is the best solvent for HC materials IMHO; using naphtha should do a fine job, just be prepared to go through a number of washes until there is no evidence of corrosion or grease evident.

If the coarse focus is a bit stiffer than the fine, that is perfectly normal and not an issue, which is very good news!

Again, perhaps I misunderstood something in earlier messages, but if the optics only have surface dust, as you say, not a problem, in fact, to be expected! Most of the Orthoplans do not come with the K4 condenser lens - not sure why but there you are! Good luck in finding one as they almost never show up on the aftermarket. Certainly the scope is fully usable without it.

Condenser Centering Screws - your surmise is correct that there are springs that are used to exert enough pressure that once the screws are released the unit will move in the opposite direction. This problem is, again, the lubricant drying and causing more resistance than the spring energy can overcome. A good cleaning with solvent should address this.

I admit to being a bit surprised the IPD adjustment moves freely, but that is good news, as is the information the optics in the headpiece are clean and free from contaminants/fungi.

My original introduction to the First Contact cleaning system was when I was involved with telescopes, and although the kit is a bit pricey, it will last a long time and nothing cleans first surface mirrors or quality lenses as well.

I strongly suggest you request a refund and list the various problems - it does not meet the criteria of being completely functional. How much depends on you and the seller coming to an amicable agreement.

The 'market' such as it is, for Orthoplans, (or for any other 'vintage' microscope) is dependent solely on how much one is willing to spend. I have seen Orthoplans go for prices as low as $150 and also listed in the multi-thousands. Here is one that sold recently on eBay (4/15/18 323210039374) for $400 plus $100 shipping that 'seems' to be a decent scope; from the same seller, another sold for $250 (323216162937) with a list of problems that might sound familiar!

I see them listed for everything from $150 up to $12K and above, but the most accurate measure of the market value is looking at completed auctions. Here is one that sold for $2,350 (253642180317) BUT is has the large circular stage, FSA50 headpiece, pol condenser, plus a complete set of quality objectives. As well, the seller is someone who I have dealt with over the years who knows Leitz microscopes well and only handles quality items. (8K+ exchanges, 100% positive with zero negative/neutral feedback.) His prices are usually at the high end of the spectrum, and worth it.

The 'extras' on the last mentioned microscope push the value up dramatically - the headpiece alone is very rare and warrants big dollars, perhaps $1K or more, and the condenser is once again, not common so attracts a lot of attention. Finally the large rotating circular stage is usually valued well above $500 by itself.

My point is it is impossible to say 'what is a good price?' as so much depends on the accessories included, the condition, etc. If I could find a solid Orthoplan with appropriate objectives (NPL or better) and lamphouse AND power supply I would expect to pay circa $1K, BUT I have paid more (>$4K for a well equipped system with multiple accessories out of a research lab) as well as much less - got one for $150 in November with two lamphouses (one Hg Vapor), complete excepting optics and now use it as my #1 microscope.

No question, with some TLC and a few $$ for objectives etc. you will have a great scope. Keep your eyes open for needed items on eBay as they do come up fairly regularly.

If you have any questions I will be more than happy to give you my input.

[JGardner]

Condenser Centering Screws - your surmise is correct that there are springs that are used to exert enough pressure that once the screws are released the unit will move in the opposite direction. This problem is, again, the lubricant drying and causing more resistance than the spring energy can overcome. A good cleaning with solvent should address this.

I took care of this issue last night and now the condenser centers properly. Another problem down and only the field iris and mirror issues to go. I'm expecting the mirror issue to be trivial and the iris to require some effort, but ultimately yield to a good flushing with solvent.

[JGardner]

I got the field iris unit out of the stand and tried soaking the whole thing in solvent. Even after six rounds of solvent, it was still frozen.

I took it apart and found that most of the blades were stuck to each other, leaving me no other choice but to remove them and soak them in solvent. They are all clean and dry now, but I haven’t discovered the trick of getting them back together. One half of the unit has a series of holes in a circular pattern and each leaf has two pins—one on the front and one on the back, and opposite ends of the blades. One pin goes in the holes on one half of the assembly and the other goes in a linear slot on the other half of the unit. I can’t figure out how to get the pins of all twelve leaves in the holes at the same time without at lest one popping out.

Anyone have any hints on how to do this? How was it done at the factory?

[PeteM]

As you probably observed in disassembly, the iris leaves go in one at a time with one pin down and the other hoping to align with slots or holes in a part above (and now likely apart, since you got the leaves out).

So you start assembly one leaf at a time -- one over another -- resting the leaves toward the fully open position -- and get maybe half way around when things start flying apart. At this point you'll want to conjure up some sort of very light clamp or restraint to hold the previously assembled pin ends lightly in place. You may have to make up something like a bit of stuff foam cut in a circular arc and held between clamp type tweezers. Whatever holds most of the already-pinned ends in place.

As you get to the last few iris leaves you need to start tucking them under the already installed leaves, fiumbling to align the pin and its hidden hole. I use a tiny spatula to lift the leaves already in place. Not so bad if you have secured the ends of the previously installed leaves. Seemingly impossible if you haven't.

After much consternation and a few tries you've got all the iris leaves with one end pinned in place. You carefully arrange them to the outer wide open position; using that as a reference so all the pins now facing up are equally spaced.

At this point you take the top portion, try to carefully drop it over the pins, jiggle things a bit, and if you're lucky capture all the upward facing pins.

Next you do something stupid like drop the entire assembly and start again -- this time with a bit more dexterity.

Not sure if this is the right way; but it has (eventually) worked for me on several scopes.

[JGardner]

Thanks for the advice.

We got it back together and it works. My wife, who’s a master at jigsaw puzzles, and who has a lot more patience than me, finessed it back together.

I also found that the 45-degree mirror in the sub stage assembly came completely loose from its mount. Fixing that should be a simple matter of cleaning off the remnants of the old glue and gluing it back on with epoxy.

[JGardner]

I got the scope back together and the field iris works, but it's a little hard to adjust via the thumb wheel. I suspect this is because it's now totally dry--I stripped all of the lubrication out of the unit when I cleaned and reassembled it. I know that the iris blades themselves should not be lubricated, but how about the other parts of the mechanism? Should they be lubricated, and if so, with what?

[75RR]

This should do:

http://www.molykoteproduct.com/pdf/en/M ... Grease.pdf
https://www.amazon.com/Corning-Molykote ... olykote+33

and yes, avoid getting any on the blades - they become dust magnets.

[JGardner]

This should do:

http://www.molykoteproduct.com/pdf/en/M ... Grease.pdf
https://www.amazon.com/Corning-Molykote ... olykote+33

I thought anything containing silicone was a big no-no anywhere near optics?

[75RR]

I thought anything containing silicone was a big no-no anywhere near optics?

I think one should always avoid grease, oil, indeed just about anything on lenses.
Had not heard that silicone grease was worse than any other. Then again this is not going near any lenses is it?
Perhaps someone can chip in on this.

[billbillt]

I thought anything containing silicone was a big no-no anywhere near optics?

I think one should always avoid grease, oil, indeed just about anything on lenses.
Had not heard that silicone grease was worse than any other. Then again this is not going near any lenses is it?
Perhaps someone can chip in on this.[/quote

I have used graphite(lightly) with some luck.. Use a sharpened pencil to apply precisely... I learned this trick in college lubricating a Pickett slide rule that I tried to wear out...

BillT

[JGardner]

Then again this is not going near any lenses is it?
Perhaps someone can chip in on this.

The field iris assembly is immediately adjacent to the swing-out lens. When the swing-out lens is swung in, it's no more than 3-4mm from the iris assembly.

[mrsonchus]

I just cleaned the field-iris of my Orthoplan - last night in fact. It was sticking and slightly deforming as it reached about 85% of it's maximum amount of closure.
Upon removal of the housing (not removal of the iris-leaves themselves individually) and inspection it transpired that in the past someone had lightly oiled two of the leaves. These two were binding and causing stiffness at the wheel as well as the distortion.

All I did was apply isopropanol liberally and gently wipe, several times, using about 20 cotton-wool buds I suppose in all. This I did very carefully indeed - the field-iris leaves of the Orthoplan are really very thin and fragile - and quite large too.

The rusty-oily-mucky stuff that was removed by this simple method was quite a surprise. Once the buds were 'coming back clean' I let the assembly dry for about 5 minutes while gently moving it from full-closure to full open and hey-presto - a perfectly smooth and fully-fixed field-iris!

As far as I'm aware the iris should indeed be completely dry and lubricant-free.

John B.

[JGardner]

As far as I'm aware the iris should indeed be completely dry and lubricant-free.

I went even further when I cleaned the field iris and completely removed all the blades and cleaned them and the other parts in solvent. Now everything is completely degreased, clean, and dry, and the iris opens and closes as expected. But it takes a lot of effort on the control wheel to move it, and I suspect that some lubrication is needed on the circular parts that rotate.

[mrsonchus]

As far as I'm aware the iris should indeed be completely dry and lubricant-free.

I went even further when I cleaned the field iris and completely removed all the blades and cleaned them and the other parts in solvent. Now everything is completely degreased, clean, and dry, and the iris opens and closes as expected. But it takes a lot of effort on the control wheel to move it, and I suspect that some lubrication is needed on the circular parts that rotate.

It could well be the case - is there a possibility that the casing that holds the wheel/control is a touch too-tightly assembled? I don't mean the leaves, just any casing that's holding the mechanism....

John B.

[JGardner]

It could well be the case - is there a possibility that the casing that holds the wheel/control is a touch too-tightly assembled? I don't mean the leaves, just any casing that's holding the mechanism....

I don't think so. When I reassembled the unit I had to back off the screws about a half-turn to get the parts to turn. Tightening them all the way binds everything up. If I loosen them any further everything will be too loose.

[75RR]

You could PM carlh6902 who has a lot of experience in refurbishing Olympus BH-2 microscopes.
See link to his step by step manuals and his list of lubricants at the end of his pdfs

viewtopic.php?f=5&t=5301&p=47741&hilit= ... ead#p47741

The field iris assembly is immediately adjacent to the swing-out lens. When the swing-out lens is swung in, it's no more than 3-4mm from the iris assembly.

Are you perhaps worried about evaporation and the fumes clouding the lenses? Do not believe that is the case with Molykote silicone grease. Do you have a reference for this if that is the case?