Help Fixing Microscope Head?

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tmasciola
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Joined: Wed Sep 23, 2020 11:32 pm

Help Fixing Microscope Head?

#1 Post by tmasciola » Thu Oct 01, 2020 5:11 am

I have a fairly old but nice binocular compound microscope that I recently damaged and need to repair a detached mirror in the head. I have no idea how to even open the head, much less repair it. Does anyone know how to open this thing up (looking at my pictures)? I really love the microscope and would love to find a cost-effective way to repair it, if possible.

Here is what happened... I was in the process of replacing a lamp bulb and and was less than careful (total bonehead move on my part), resting the microscope on its back side. It slipped and fell to the side, hitting the left side of its head on the table, jarring the head and disconnecting one of the mirrors inside (it looks like the mirror to the right side of the left tube). From what I can see, the mirror does not seem to be broken -- the epoxy that held it onto the tube disconnected. I knew what happened because the left eye tube went black and I heard the mirror clinking inside. Although I can see and touch it through the tube, the mirror is too large to extract and I see no way to open the left housing that it is inside. No screws, no snaps, no obvious way to disassemble the housing (possibly interlocking sections?) I don't see cracks or obvious damage to the mirror, but it's hard to be sure. While I figured things out, I carefully stuffed a cotton cloth into the tube between the two mirrors (the other mirror looks fine) to prevent them from touching or getting further jarred. I am currently able to use the right eyepiece just fine and the left mirror doesn't seem to be moving thanks to the cloth.

I am a reasonably handy person, but I know almost nothing about the internals of a microscope. I am learning quickly, because I recently tore apart the base and fabricated my own gear to replace the original one that had worn out (reassembling and lubricating the bearings and assembly inside) and it seems to be doing ok. Like I said, I really love this microscope and with the quality of this thing (sturdy construction, nice optics, smooth mechanical stage etc.), I'd don't want to give up on it yet if I can avoid it.

Does anyone know how to open the (left) black box that surrounds the tube? I see now screws or anything to get me started. But once I open it, I'm hoping I can epoxy the mirror back in place. Please look at the pictures and let me know if you can help. Thanks!
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PeteM
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Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: Help Fixing Microscope Head?

#2 Post by PeteM » Thu Oct 01, 2020 6:33 am

I've seen two ways of removing covers. Some have screws. Others have a snap fit; requiring you to carefully try lifting a corner with a thin blade or a tiny (beat up jewelers?) flat head screwdriver. Could also be that some covers have adhesive, but I haven't seen that yet.

In some cases you need to remove a central round decal or cover (where the interpupillary distance marks are) to expose screws below that allow separating the binocular parts. Those may have a rubbery adhesive and are possibly meant to be pried off.

If you're lucky, once inside, you'll be able to see (from glue residue) exactly where to replace the mirror. Not sure I'd use epoxy though. If the mirror is solidly attached to aluminum, differences in the rates of thermal expansion between glass and aluminum might eventually crack the glass. Aluminum has near 3x the index of thermal expansion. And if you screw up placement, removal is going to take some glass with it if you have a proper epoxy bond.

I've done glass to metal repairs with three approaches, all of which seem to be holding up. All require carefully noting position, scraping away the old adhesive, and cleaning up for a good bond (isopropyl alcohol likely).

- Using tiny drops of a rubbery cement with a bit of give for DIC prisms and first surface mirrors.

- Using cyanoacrylate (instant glue) with a bit of 1/2" round paper blotter in between the glass and aluminum (to give a bit of give and a central adhesion point) for Cycloptic stereo microscope prisms. This allows quick setting and also easy immediate repositioning with acetone as a solvent. Not likely right for your mirrors, though, which may have both a mechanical capture (screws, straps) and (prior) adhesive to hold things in place.

- Most recently using E6000. Not enough time has passed to judge it, but it seems to working OK. Put a drop on cardboard and place it with something like a toothpick. Biggest problem is it dries quickly with tiny "spider threads" dragging behind that you might have to work around. Seems stronger and just as flexible as the rubbery cements, though.

Others may have better advice or an OEM source of adhesive. A spot of epoxy or other hard glass adhesive should also be fine if you don't constrain the entire bit of glass - just one spot, maybe part of one edge?

Is that a Tiyoda or ?? scope. Someone with the same scope might be of greater assistance.

Element 56
Posts: 272
Joined: Thu Oct 13, 2016 3:48 pm
Location: Lancaster County, PA

Re: Help Fixing Microscope Head?

#3 Post by Element 56 » Thu Oct 01, 2020 8:41 pm

What exactly are you working on? Brand serial number etc...

tmasciola
Posts: 4
Joined: Wed Sep 23, 2020 11:32 pm

Re: Help Fixing Microscope Head?

#4 Post by tmasciola » Mon Oct 05, 2020 11:28 am

Thank you so much for your help! I'm sorry, I didn't get a notification so I didn't realize anyone replied. That was very thorough and helpful feedback. When I get back in town, I'll try to pry off the round plate with the IPD markings. I hesitated to try that before asking because I didn't want to break anything. Good, if it was meant for that.

I think it is an American Scientific Products M3000, which I think was later acquired by Baxter so is similar or identical to Baxter M3000. If anyone knows more about the case prying part, it would be great, as it's a bit old and I expect may take a bit of effort to pry apart. I don't want to break it. Thanks!

apochronaut
Posts: 3561
Joined: Fri May 15, 2015 12:15 am

Re: Help Fixing Microscope Head?

#5 Post by apochronaut » Mon Oct 05, 2020 12:10 pm

How do you know they are mirrors?

tmasciola
Posts: 4
Joined: Wed Sep 23, 2020 11:32 pm

Re: Help Fixing Microscope Head?

#6 Post by tmasciola » Wed Oct 07, 2020 12:43 am

I guess I don't know for sure but it looks like a mirror, or at least a lens of some sort. There is one mirror in the tube, slanted at an angle on the outside edge of the tube and this one is still attached with no obvious issues. Then it seems like another mirror (the one I'm referring to), that seems to oppose the other mirror in the tube and is detached. I can neither remove it from the tube (because it's too big) or reattach it from this vantage point. I hope that if I can open the casing, I can reattach the mirror/lens and get it back to normal. I guess I assumed that both "mirrors" work together to redirect the light from the microscope to the ocular tube. Hope this helps.

apochronaut
Posts: 3561
Joined: Fri May 15, 2015 12:15 am

Re: Help Fixing Microscope Head?

#7 Post by apochronaut » Wed Oct 07, 2020 2:40 pm

Yes. That's the way it works. Some heads use prisms instead of mirrors or a combination. I guess you can see that it is a mirror for sure by looking down the tube?

tmasciola
Posts: 4
Joined: Wed Sep 23, 2020 11:32 pm

Re: Help Fixing Microscope Head?

#8 Post by tmasciola » Wed Oct 21, 2020 11:03 pm

Sorry for the delay in getting back. I came back from my trip and got swept up in work. I finally had a chance to try things out today and it looks like I am still stuck. Sure enough, I was able to remove the plate with the IPD markings on it by prying it off (thanks PeteM), but what I saw underneath didn't seem to give me more screws or options to open it up.

See the attached photos, which show where I am now (they show both open ends of the central tube). I have the plate off and the prism section removed. I can see clear through the central tube, but still I have zero idea how to open the ocular cases (which is where the issue is). Everything I attempt to pry just ends up chipping off paint and not budging, so if someone can please tell me from experience which part needs to be pried open (and how), I'll feel better before introducing more damage.

Does this look familiar to anyone? Any guess where I can pry the ocular case open? Thanks!
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