AO Cycloptic Magna-changer stuck?

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Wehnelt2
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Joined: Thu Jun 24, 2021 5:56 am

AO Cycloptic Magna-changer stuck?

#1 Post by Wehnelt2 » Thu Jul 29, 2021 3:07 am

Hi. I'm in the process of refurbishing an AO Cycloptic but ran into an odd problem. The Magna-changer is stuck and doesn't rotate, though it doesn't appear to have anything blocking it such as the detent spring or corrosion on the barrel and the other mechanics are in terrific shape. Did some models have an optional grub screw to lock the Magna-changer in place? It is stuck on a high zoom level, or did they sell some that still used the Magna-changer barrel but only had 1 high zoom that didn't rotate(seems unlikely since the detent springs are aligned and greased).

dtsh
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Re: AO Cycloptic Magna-changer stuck?

#2 Post by dtsh » Thu Jul 29, 2021 3:22 am

The manual lists a model "F" with a single fixed magnification. I've not seen one, so I don't know if it uses the magni-changer. It is listed as having 15x with 10x eyepieces and 20x with 15x eyeieces. I presume the magni-changer comes off like the others, remove the screws in the middle of the magni-changer dials and they should come off, allowing the changer to be slid out the side opposite the detent spring.

It doesn't sound like what you describe is the same as the F, so my guess is it's stuck. Some pictures might help.

Mine is an "M", but if you need me to look at some particular part let me know.

Wehnelt2
Posts: 6
Joined: Thu Jun 24, 2021 5:56 am

Re: AO Cycloptic Magna-changer stuck?

#3 Post by Wehnelt2 » Thu Jul 29, 2021 4:45 am

Thanks - I found the '77 manual (I'd only seen the brochures) and mine is a 59M. It will rotate a couple degrees but then is hard stuck even with the pin-detent manually depressed- which is why I thought there might have been a locking pin/grub somewhere that I was missing. The manual page 7, item 6 is a "Stop Screw", I'll check that*edit* stop screw is for the eyepiece IPD adjustment. It's a former ATT and then University scope, Factory Service Keene, N.H., with someone having scribed FN-299005-57AA into it. Would my next step be to use a right-angle lock ring pliers to unscrew the hinge pin and carefully check to see if something is physically blocking rotation? tyvm.

*update* I didn't see anything physically blocking it, though there may be hardened gunk underneath from it being in storage without the CMO attached. Should I use a gentle solvent around the barrel rim? I'd need to quadruple check the pathways to avoid a solvent dripping or pooling onto any lens assembly and find the appropriate solvent. I'm not experienced with using solvents to remove lubricants, especially ones older than myself.
Trying to wiggle it back and forth resulted in the main knob's Delrin fatigue cracking quite easily(dang) and quickly so it's probably been stuck or had increased turning resistance for awhile before it came to me.
MagnaSide - small.jpg
MagnaSide - small.jpg (73.91 KiB) Viewed 3186 times
MagnaDetent small.jpg
MagnaDetent small.jpg (101.56 KiB) Viewed 3186 times

apochronaut
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Re: AO Cycloptic Magna-changer stuck?

#4 Post by apochronaut » Thu Jul 29, 2021 2:07 pm

Likely the grease has hardened and is resisting movement. The fit between those drums and the cylinder is quite tight and it is aluminum on aluminum, so without the correct viscosity of lubricant or very close to correct , they will bind easily. Dried lubricant can pack up too. This would allow some movement to a lockup.
I would introduce a very small amount of a light solvent at both ends and with some wiggling you should be able to push the drum out from the detent side.
The cracked collar on your dial(s), I have repaired by cementing the piece(s) in place with epoxy, then grooving the outside of the collar slightly and twisting a thin brass wire ring tight on it to make a clamp. Be carefull not to plug the registration hole.
The magnification plates are left and right. Sometimes they fall off the knobs and can accidentally be put on the wrong side.
Just an adjustment note. Often the objectives are aligned along the y axis but don't line along the z axis. Those 6 registration bars that detent into the spring can be loosened individually and moved clockwise or counter clockwise in order to perfectly align the objective centers.

Wehnelt2
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Joined: Thu Jun 24, 2021 5:56 am

Re: AO Cycloptic Magna-changer stuck?

#5 Post by Wehnelt2 » Fri Jul 30, 2021 12:52 am

Thank you for the help. I have a 3d printer so planned to fix the knob by making a support ring attached by epoxy and epoxying the split section back together, followed by drilling a new registration away from fatigued material and rotating the label on the knob accordingly.

Is 90% IPA an appropriate solvent?

apochronaut
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Re: AO Cycloptic Magna-changer stuck?

#6 Post by apochronaut » Fri Jul 30, 2021 1:08 am

You could try it just to get the drum out because of it's relative safety, if that is already what you have......in case some got into a lens or two. IPA isn't a particularly good solvent of grease or oil but it might do that little job o.k.
Once you get the drum out most of the cleanup can be done dry. Much detailed work can be done with a small toothbrush and dish detergent.
Damping grease is often called for on many microscope parts. I found the one I currently have to be too heavy for that drum. The last one I did I used vaseline on. You really don't use much and on just the obvious mating surfaces that act like bushings.

dtsh
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Re: AO Cycloptic Magna-changer stuck?

#7 Post by dtsh » Fri Jul 30, 2021 2:14 pm

Once the changer is out, if you need to clean any of the lenses I found on the "M" changer I could reach all the exposed inner surfaces through the empty positions; I found bending a cotton swab was helpful. Be aware that if you remove any of the lens elements from the changer like I did, it will probably take some repetitions and effort to realign them.

Wehnelt2
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Re: AO Cycloptic Magna-changer stuck?

#8 Post by Wehnelt2 » Sat Jul 31, 2021 9:35 am

No luck with the IPA. I used about 0.25-0.5mL Naptha/Petroleum Distillate by filling the aerosol straw then touching the straw to one side of the barrel and it wicked to the opposite side overnight with some dark gunk coming out with it, rotated the base, and repeated from the other side. It was mostly clean the second time but with no movement. It feels like something that would usually need a bearing puller but that seems excessive and likely to break the Magna-changer's Delrin. I'm also not sure how much tapping the mechanism can withstand other than to avoid high-g forces in general with optics.

apochronaut
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Re: AO Cycloptic Magna-changer stuck?

#9 Post by apochronaut » Sun Aug 01, 2021 4:24 pm

I suppose it is theoretically possible that one of the screws that holds objectives in the drum has vibrated out and is jamming it. Can you move the drum back and forth a little or have you just gone forward to lockup?

Wehnelt2
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Joined: Thu Jun 24, 2021 5:56 am

Re: AO Cycloptic Magna-changer stuck?

#10 Post by Wehnelt2 » Fri Aug 06, 2021 9:18 pm

It appears to be locked solid. It makes me wonder if the rotational movement I was feeling at the beginning was actually just the delrin knob's crack separating and coming back together before failing completely.

PeteM
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Re: AO Cycloptic Magna-changer stuck?

#11 Post by PeteM » Sat Aug 07, 2021 1:29 am

You might try a bit of heat (pencil type heat gun) to the outer body to expand the space a bit and try a drop or two of something like Kroil penetrating oil. Outside housing blow dryer hot. Inside barrel kept cool as you can. Try to rotate it just a degree or two in one direction and then the reverse direction. You want to gradually loosen up any oxidized grease rather than try pulling or rotating the whole thing out with brute force.

IPA isn't a particularly good solvent for grease. For future reference, a relatively safe and conveniently packaged one is lighter fluid. What you used should be good (and very similar to lighter fluid), but it's entirely possible it found a single channel through and left large patches of congealed grease in areas of the barrel.

Since the most common failure mode with Cycloptics seems to be detached prisms, perhaps followed by a broken detent spring, the good news is that even if you have a mangled part - you can probably get a replacement scope with a good inner assembly fairly affordably.

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