Need help with Optiphot 2 (stuck field iris)

[Dubious]

I'm trying to get at and oil the seized field diaphragm iris on an Optiphot 2--the knurled adjustment ring won't turn at all. Does anyone know how to disassemble it? I've removed the top ring with the graduations (3 screws) but the adjustment ring won't come out. Before using more force, I thought I'd better seek advice. Any suggestions would be most appreciated.

[Hobbyst46]

Perhaps the downloadable repair manual refers to it ?
see ​viewtopic.php?f=25&t=7903&p=69669&hilit ... ian#p69669
(post #6)

[PeteM]

My recollection is that you might have to reach this from the bottom.

In general, the leaves of an iris don't want to be greased or oiled. The pins, perhaps. Once you get it out you might try to loosen it up with a solvent (say, lighter fluid) and try to get rid of any hardened grease. A foam swab, running so it glides over the leaves rather than catch their edges can help mop up whatever gunk (now loosened by solvent) had it stuck.

[MichaelG.]

In general, the leaves of an iris don't want to be greased or oiled. The pins, perhaps.

Amen to that ^^^

The seizure is likely due to evaporation>migration>solidification of what tiny amount of lubricant was originally used.
High power tungsten illuminators provide plenty of heat to do this

MichaelG.

[Greg Howald]

I wonder about heat. If the diaphragm is of all metal construction, a little heat shouldn't cause it any harm. After all, it's already stuck. If the problem is caused by a seized lubricant, heat may serve to liquify the lubricant and free the apparatus. You might bake it in the oven at about 170 degrees F. That might loosen it, and 170 degrees shouldn't cause any harm.
You might otherwise soak it in a solvent to liquify the seized lubricant.
Geez, I hate trying to take those things apart. That's just got to be the last result. It's not taking them apart that is difficult. It's the putting back together part that's hard.
Greg

[imkap]

If it's a lubricant problem, you can use a contact cleaner. I have wd40 contact cleaner and it did the job for me with a stuck iris...

[Dubious]

Thanks for the suggestions. I downloaded the repair manual. Its diagram of the top parts of the field diaphragm assembly is a bit ambiguous (and possibly for the Optiphot 1) but it shows a "retaining ring" on top, right under the adjustment ring. I also loosened the mirror box down underneath, and it now seems to be held only by the top rings. I have put a few drops of oil on the top rings; and after giving that time to seep in, I'll apply some heat with a hair dryer and see if anything has loosened.

I must say, the Optiphot 2's 100w lamp produces a LOT of light. After struggling with 20w and 30w lamps that produce barely enough light in some modes, I thought it would be nice to have plenty of light; but, at least so far, the 100w lamp seems overkill. Well, I guess that's what ND filters are for...

[Hobbyst46]

Thanks for the suggestions. I downloaded the repair manual. Its diagram of the top parts of the field diaphragm assembly is a bit ambiguous (and possibly for the Optiphot 1) but it shows a "retaining ring" on top, right under the adjustment ring. I also loosened the mirror box down underneath, and it now seems to be held only by the top rings. I have put a few drops of oil on the top rings; and after giving that time to seep in, I'll apply some heat with a hair dryer and see if anything has loosened.

I must say, the Optiphot 2's 100w lamp produces a LOT of light. After struggling with 20w and 30w lamps that produce barely enough light in some modes, I thought it would be nice to have plenty of light; but, at least so far, the 100w lamp seems overkill. Well, I guess that's what ND filters are for...

I somehow recall that the Optiphot-2 standard transmittance lamp was 50W; might be wrong though.
Also, the plastic piece that connects the lamp housing to the stand is brittle and tends to crack and disintegrate over time, possibly due to the lamp heat.

[PeteM]

The original Optiphot (1) had a 50 watt lamp. The Optiiphot 2 went to 100 watts. Either one is bright enough for most any use.

Both are typically wonderful scopes, as long as the plastic fine focus gear hasn't been damaged or has been replaced. The possible problem with the lamp house at back is compounded when people set the microscope down back end first. Of the nearly dozen Optiphots that have passed through, only one had a cracked housing - while more than half had to have the fine focus gear replaced.

[Dubious]

On this one, the lamp housing is intact and not cracked, although I can see it could be easily damaged, as it protrudes so far--another reason maybe to prefer the Optiphot-1 with its much smaller metal housing. Fine focus seems to work fine, although I haven't used it much yet.

[Dubious]

Applying some heat with a hair dryer did the trick; oil oozed out and the adjustment ring on the field diaphragm began to turn a bit. I was then able to work it up and off (I had already removed the top ring with the graduations, secured by 3 screws). That released the mirror box assembly in the base (I had already taken off its 4 screws). Fortunately, the iris diaphragm, on the other side of the mirror, operated by a toothed half-gear, was fine when operated directly, so I didn't need to do anything to it. I did have to put a little work into rubbing off the sticky residue of hardened oil on the top rings. After cleaning and reoiling the moving parts, I put things back together, reassembled the microscope; and now the field diaphragm moves smoothly.

[MichaelG.]

Good result

MichaelG.

[Dubious]

I had some luck, of course--I didn't break anything, and it turned out the iris blades were not stuck, corroded or otherwise damaged--luck is always important in these endeavors Also, thanks to everyone for the helpful information and suggestions.