Repair or parts manual for Leica MZ6 stereo microscope?

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PeteM
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Repair or parts manual for Leica MZ6 stereo microscope?

#1 Post by PeteM » Fri Nov 19, 2021 3:12 am

A Leica MZ6 zoom body arrived today, claimed by the seller to be in great shape except for the sun-yellowed plastic body. It turns out that the zoom is only parfocal at the very lowest and the higher magnifications. Everything in between is way off. Far as I can tell (OK, guess), the problem is a tiny missing bearing meant to ride on a brass cam that moves an intermediate pair of lenses into proper position. All that is there is a stub of a tiny axle that looks like it might need something like a 6mm diameter bearing to reach the cam?

Before returning it - does anyone have experience with this problem -- or a PDF of a parts diagram or repair manual that might help me identify the missing bearing (if that's the problem) and the original method of attachment?

Many thanks on the remote chance someone can assist.

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75RR
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#2 Post by 75RR » Fri Nov 19, 2021 7:17 am

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Probably way off on this theory but thought it worth a shot. Could the Ratchet settings be messing things up?
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MZ6 Ratchets.png
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Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

PeteM
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#3 Post by PeteM » Fri Nov 19, 2021 8:15 pm

I appreciate the idea, but pretty sure it's not the click stops. The focus is out with our without them actuated. In the photo below, I've inserted the end of a swab between the yellow brass cam and the "axle" that might once have had a cam follower (bearing). One can see damage around the area. My guess is that some sort of tiny bearing belongs here.

I navigated Leica telephone support, got a person who directed me to the "right" phone extension, spent half an hour on hold, and then got a support person who said they have some parts lists/diagrams but not this one. He promised to put in a note and have someone email or call me back. We'll see.
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LeicaMZ6_bearing.jpg
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viktor j nilsson
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#4 Post by viktor j nilsson » Fri Nov 19, 2021 9:01 pm

The zoom mechanism on a MZ8 failed when I was working on it a couple of years ago in a lab in Toronto. Some plastic part just snapped while zooming. It was fixed quite promptly by Leica's representatives, but it made me certain that I'd never buy a plastic Leica stereo microscope for home use. But at least it shows that Leica know how to fix some issues on these scopes - at least for paying customers.

Scarodactyl
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#5 Post by Scarodactyl » Fri Nov 19, 2021 9:30 pm

The ones I've messed with have been pretty well built. The insides are mostly metal, though I have never messed with the mz8 in specific and it was one of their older designs. Maybe some of the gears are plastic, breakage of which is a common complaint on the mz16.

viktor j nilsson
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#6 Post by viktor j nilsson » Fri Nov 19, 2021 9:39 pm

Yeah, I may absolutely have jumped to conclusions based on too small a sample size. I've never taken one of the MZ's apart and just assumed that my experience was symptomatic for the MZ range. The plastic exterior doesn't exactly inspire confidence! But good to hear that some or most are better built than I thought.

PeteM
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#7 Post by PeteM » Fri Nov 19, 2021 10:10 pm

The interior of the MZ6 looks reasonably well built. Metal frame, nicely machined guides, and so on. Better than Chinese zoom scopes I've opened up. The "ESD safe" plastic housing is a clamshell that easily removes with screws top and bottom. Biggest problem with it is an apparent lack of UV stabilizers -- it has yellowed with age and perhaps become slightly brittle?

The missing bit on mine is a puzzle. The other moving pair of lenses has a tiny cam follower. The pair of not-adjusting-properly lenses that is my problem looks to have a tiny missing cam follower of unknown (tiny ball bearing, plastic, metal) composition with no obvious means of attachment. There's just a tiny tear in the metal axle area where I presume it fit. Could have been glued or press fit or ??? In any case, not likely a good design.

This one is going back - not worth further effort to attempt a repair. If Leica comes through with a parts diagram, I'll aim to update this post on the missing bit.

Scarodactyl
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#8 Post by Scarodactyl » Sat Nov 20, 2021 2:11 pm

Yeah, that's not an easy fix. It was likely abused pretty badly to do that, which is a common refrain with stereos.

PeteM
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#9 Post by PeteM » Sat Nov 20, 2021 6:32 pm

What's annoying on this one is that the optics and mechanism are otherwise in good shape. The housing is seriously yellowed from sun exposure, but it's just this one part that has apparently broken off. Getting inside to work on this was also a breeze - one of the rare not overly-complicated Leica designs.

I see from Ebay "parts only" listings (this one was promised good) that a trashed zoom focus is pretty common. In roughly trying shims, it was also apparent that one had to get the cam follower of just the right diameter to to keep things parfocal. Get it off a bit and you can't even get a proper manual focus.

If someone ever has a Wild/Leica M3Z opened up, I'd be interested to see how that cam follower was designed.

PrecisionInstruments
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#10 Post by PrecisionInstruments » Sun Nov 21, 2021 6:51 am

Definitely a roller bearing should be rolling over the brass cam, which should be pressed over that stub as you have thought.
Although having serviced thousands of MZ6’s, I have never taken measurement of the roller bearing, not ever had to replace one. I would estimate the roller bearing to be approx 3-4mm outer diameter.

The older style Mseries would simply had a thick plastic tube in the roller bearings place. Maybe to gauge the correct diameter roller bearing, you could apply multiple layers of heat shrink until you gain parfocality and therefore the correct diameter, of course making sure you have adjusted the eyepieces correctly first.
I have a headache, For which the future’s made

PeteM
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#11 Post by PeteM » Sun Nov 21, 2021 7:44 am

Thanks for that information, PrecisionInstruments.

PeteM
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#12 Post by PeteM » Thu Nov 25, 2021 1:19 am

Here's what I've learned, not quite willing to give up on this.

1) Leica was good enough to get back to me, but they didn't want to share repair manuals with a hobbyist and don't stock any parts for this scope.

2) On a hunch, I searched around here for the smallest ball bearings I could find. They're .2495" OD (approx 6.33mm) with a flange. The flange seems to capture the bearing between the shaft and the brass cam. If so, not as bad a design as I initially thought. The MZ6 ends up almost perfectly parfocal through the zoom range with this bearing in place, though it's just a bit loose and off center. A guess is that a 6mm bearing is what was called for.
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Small flange bearings.jpg
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LeicaMZ6bearingINplace.jpg
LeicaMZ6bearingINplace.jpg (50.84 KiB) Viewed 238 times

PeteM
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Location: N. California

Re: Repair or parts manual for Leica MZ6 stereo microscope?

#13 Post by PeteM » Sun Nov 28, 2021 5:25 am

Turns out that a 6mm OD flange bearing works perfectly - parfocal throughout the zoom range.

Scarodactyl
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Re: Repair or parts manual for Leica MZ6 stereo microscope?

#14 Post by Scarodactyl » Sun Nov 28, 2021 6:14 am

Congrats! The mz6 is a nice scope when it's working.

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