AO Sterostar Prism

[pilot2]

I have an AO Stereostar microscope. Haven't used it for several years but now using it to solder surface mount (SMD) electronic parts to PCB's. The right side works fine but the left side does not. I have swapped eyepieces, inspected the 3 levels of optics. It doesn't seem than anything is optically blocked or moved. I think the problem may be that the left prism has moved.

How do I remove the body (I think that's what it is called) to gain access to the prism? Then how do I adjust the prism?

[apochronaut]

Which model, although I think they are all pretty similar and I also think they all used first surface mirrors. Possibly, a mirror has lost it's footing. Don't shake it or move it a lot. The mirror could be irreparably damaged. If you are lucky, the original glue joints will be intact with decent margins and you can just set the mirror back in place and epoxy it in.
But before you dig into that, make sure all of the lenses in the zoom body are intact. Especially the front lens. It is cemented into it's mount and after 40-50 years one can drop out, leaving the mount behind. Look at the two lower lens housings and make sure both are in there.
If all is well, you then have to unscrew the zoom body shroud by removing the cheese head screws in the mounting flange and then have a look at all the lenses, making sure the two sides are symmetrical. Then loosen the zoom knobs and pull them off. The latter is a little tricky. There is a small hex lock screw as well as a long slot head travel stop pin to remove. Sometimes the knobs are stubborn. You can then remove the hex bolts holding the zoom body and lower it away from the binocular head. Examine it carefully because it is just as likely that a lens in the zoom body is the culprit.
There are a couple of polarizing filters on a bracket between the head and objective array. One or both can shrivel and reek havoc with the image . Remove them if they are faulty. That might be your problem right there.
The binocular head is opened up by removal of the two large pin nuts around the optical tubes. There are clutch washers. Keep the order of everything. That allows the head cover to come off.

[apochronaut]

There is an ebay merchant from China that sells glass polarizing filters of various sizes. I replaced the filters in a modal 580 for about 20.00 through him.

[pilot2]

Here are some photos before I start disassembling. Correct me if I am wrong, but it looks like all the lenses in the photos are attached and in the correct positions. I don't see how the left/right side bodies or eyepiece holders are removed. There are no screws. Are they just press-fit?

Lower Lenses
https://link.shutterfly.com/9VAczOxIOGb

Zoom Lenses
https://link.shutterfly.com/4qVG8tBIOGb

Upper Lenses
https://link.shutterfly.com/fIfyfQDIOGb

Eyepiece Holders
https://link.shutterfly.com/qjSsCPGIOGb

Left & Right Bodies
https://link.shutterfly.com/oSsiz2JIOGb
https://link.shutterfly.com/KH0cnYKIOGb

[wabutter]

One of the biggest criticism of the StereoStar, especially from B&L dealers was there isn't an easy way to get into the body and do any alignment or adjustments to the optics. Of course, the argument of the day was with the StereoStar, you didn't need to do that, it stayed in alignment. LOL. As pointed out though after 50 years, it is possible that some adhesives failed. The Zoom 4 and 6 often needed touching up, and this was source of revenue and reason for the dealer's being, especially when B&L had the major market share as compared to AO in the stereo segment.

[pilot2]

One of the biggest criticism of the StereoStar, especially from B&L dealers was there isn't an easy way to get into the body and do any alignment or adjustments to the optics.

So will I be able to disassemble it or do I need special tools?

[wabutter]

I have never tried to take one apart, but I think Apochronaut did a nice job of explaining what should be done. Typically fittings were all imperial sizes and I am not aware of any special tools that are required.

[apochronaut]

No special tools. The 3 cheesehead screws need a good 3/16" flat head screwdriver. The hex lock screw on the zoom knobs is 1/16". The stop screw( if present because sometimes repair people leave them out, allowing the zoom drive to completly bottom out) is a small slot head.
The zoom mechanism hex mount screws are 9/16".
The pin nuts can be loosened in various ways because once loose they spin off quite easily. They can be tight. I have used a drift punch to get one loose. The ttick comes in reassembly, where they need to be just so. Tight enough to assure alignment but loose enough to allow esse of movement. There are clutch springs in there and a damping grease is recommended.

[pilot2]

I never heard the term "cheese head screws". But I deduced that they are commonly called "socket cap screws" (mine are hex socket not flathead).

https://us.misumi-ec.com/vona2/detail/2 ... XQEALw_wcB

What is "damping grease"?

[apochronaut]

I never heard the term "cheese head screws". But I deduced that they are commonly called "socket cap screws" (mine are hex socket not flathead).

https://us.misumi-ec.com/vona2/detail/2 ... XQEALw_wcB

What is "damping grease"?

Cheese head screws are like a round block of cheese, a thick disc with a slot in them. There are slot type sockets that work in them. They may have used hex screws too. I just have only encountered cheese head types. The last one I fixed was branded Reichert and black, so post 1985.

Damping grease is a thick gresse used to lubricate and clutch st the same time. It is used where there is a need of lubricant on moving contact surfaces while requiring a smooth predictable movement as well. Gear tracks, sliding tubes, helical screws. The focusing helical screw on a camera lens uses a damping grease. Petcocks or stopcocks and gas valves use similar.

[pilot2]

The set screws for the zoom knobs are extremely tight. I expect that I would strip them before they break loose. But the zoom lenses and everything below appear to be the same left-to-right. Only the left side is bad so I am making the assumption that the lower lenses are OK and removing the zoom knobs is not necessary.

I started this thread guessing that the prisms in the stereo bodies are the problem. As noted, they are probably mirrors and not prisms. So I want to get access to them. I have removed the spanner nut and 1 washer on the left (bad) side. It looks like there might be a locking ring holding the body in place. A gap in the ring is visible in the photo. If it is a locking ring I can try removing it using a dental pick. The body does not slide out easily so I want to check before forcing it. Does it just slide out? Is there a locking ring that must be removed. It is very stiff when I try to rotate it so maybe I am not applying enough force. I am being very cautious and asking rather than breaking something.

https://link.shutterfly.com/3NH6n6tYWGb

[pilot2]

This is a follow-up to my last post with new information. As a reminder, the right side is working perfectly. The problem is with only the left side.

I was able to remove the left and right stereo bodies. The grease was dry so it required a bit more twisting and pulling. They are now both off. When looking through the eyepiece holes from the top (eyepieces removed) I see a small clear image of what is below in both left and right bodies. So it appears that the mirrors are in the correct position and this is not the problem area.

With the lower lenses removed (attached to the cover) I looked down through the holes where the stereo bodies mount and through the zoom lenses. The images for both left and right were very clear. Also, images through the lower lenses (attached to the cover) are very clear.

It seems that I have tested all the lenses and mirrors individually and they all tested perfect. Then I re-installed the lower lenses and the left/right stereo bodies. Right side is perfect; left side still bad. So now I am stumped. What is the problem?

[apochronaut]

Have you looked carefully to see if the very bottom lens has dropped out and been lost. It is just the bottom element not the entire lens.

[pilot2]

I inspected the lenses at the very bottom and they appear to be in place and not shifted (see photo). When the scope is rotated there is nothing rattling around inside so apparently nothing has come completely loose. Maybe something has shifted. But all looks good to me. I am stumped.

https://link.shutterfly.com/KbTaJnSuYGb

[apochronaut]

When you say bad, do you mean dark, bright with a discernable but blurry or poor image or bright with no image at all, when the right side is focused properly on an object.

[pilot2]

When you say bad, do you mean dark, bright with a discernable but blurry or poor image or bright with no image at all, when the right side is focused properly on an object.

When the right side is focused the left side is not blurry but bright and totally undiscernable. I am viewing a green circuit board and the left image is green but appears streaked. Like a painting after water has washed across it. I cannot make out any details - not even close. Hard to describe.

[Scarodactyl]

You might have delamination or oil on one of the lenses. What type of stereostar is it? To figure out where it is you can remove the ryepieces, shine a light through the bottom lenses and look through the eyeholes (careful not to shine the light directly into your eyes so you don't get dazzled).

[pilot2]

I shined the light from a cell phone up from the bottom with the eyepieces removed. I moved the light so I was not looking directly at the bright light. The good side was generally black (or dark gray) with a clear sandy image. The bad side was not as clear and was far less sandy.

I removed the stereo bodies and the middle lenses (those attached to the cover with the cheese head screws). Only the very bottom and zoom lenses were remaining. As before, the good side had a black sandy image. The bad side was similar in color but definitely not as sandy.

I did not adjust or remove the zoom lenses.

[apochronaut]

Which model is it?

[pilot2]

Not sure what the model number is. Here are photos that may help. There is a data plate on the bottom that reads "248896". Maybe model number? Maybe S/N?

https://link.shutterfly.com/SxYxB3fUYGb
https://link.shutterfly.com/rfDU7unUYGb
https://link.shutterfly.com/3X05q0oUYGb
https://link.shutterfly.com/PSsgh1pUYGb
https://link.shutterfly.com/rzX7kZqUYGb
https://link.shutterfly.com/FiBQ2msUYGb

[apochronaut]

It looks like s 580 to me,. The rear plate that you accessed . Was there a bracket attached to that?

[pilot2]

Not sure what "rear bracket" that you mean.
The one that covers this opening to access the zoom lenses?
https://link.shutterfly.com/KX5UJCL7YGb

If so, there is a bracket holding 2 lenses
https://link.shutterfly.com/kPUnXEO7YGb

[apochronaut]

The latter. Those are actually polarizing plates and they can delaminate, messing up the image. Try removing them and see what happens.

[pilot2]

The latter. Those are actually polarizing plates and they can delaminate, messing up the image. Try removing them and see what happens.

I did remove them when testing with light from the bottom (see post Feb 6 @ 3:23pm). It seems that the problem is below them (zoom or bottom lenses).

[pilot2]

SUCCESS!

With a lot of help from apochronaut I found the problem and made the repair. The issue was that one of the lower lenses had moved (see photo). I tapped it back into place and the problem disappeared. The old adhesive was sticky enough to hold the lens in position for testing. After getting everything back together I put a very small dab of 5-minute epoxy on both lower lenses (the good one for precaution).

https://link.shutterfly.com/mbsjaQulrHb

During the debugging process the 2 prism bodies were removed. I found a lot of powder inside and cleaned them. The prism bodies are held in place with spanner nuts. I decided not to remove the zoom assembly to get straight-on access to the spanner nuts for fear of creating more problems. The only access was through a side cover which made starting the spanner nuts quite difficult. I had them on and off several times so after some practice installing them became very easy. I also used a Dremel to add 2 more notches to the spanner nuts (4 total) and that made it much easier to install and tighten.

I cannot thank apochronaut enough for his help. He has had direct experience with this scope. We emailed a number of times and spoke on the phone. Without his help I would still be trying to fix the scope.

[Scarodactyl]

Congrats! Incide tally I have a trinocular attachment for this model--if you ever want one drop me a line. They're kind of rare but I can sell it reasonably.