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williaty
1-Feb-2019, 17:34
I bought a Bausch and Lomb Tessar Ic today that I hope turns out to be a good deal in the end. The lens was hazy but my experience with previous B&L Tessars is that I could easily open them and clean the haze away. The rear cell thankfully turned out to only have haze on the outside surfaces. The front cell, sadly has haze on the internal surfaces too and I can't figure out how to get the damned thing open. The front lens is slightly loose/rattly and it looks like the crenelated ring with the inscribed lens info should screw out of the barrel but it won't budge. Any ideas on what to do?


Crappy cell phone pic of the victim:

https://i.imgur.com/WbRkSLm.jpg

c.d.ewen
1-Feb-2019, 19:02
There's always a hint - see the knurling on the top of the piece holding the beauty ring in? Get yourself a big rubber stopper or something else to get some friction on that ring and start turning. There are marks in the knurling at 10 and 1 o'clock. I can't tell if they're notches for a lens wrench or not. Check it out. If there are notches at 180 degrees, you've got your answer.

Charley

williaty
1-Feb-2019, 19:51
I have been trying with the rubber "lens wrench" cones and no luck. I'm twisting the hell out of it but the cone eventually just squeaks across the metal ring. I think the deeper marks in the crenelations are damage, not notches for a wrench but I'll inspect it to see if there's an opposing pair.

I'm freezing it now to see if it'll come loose in the morning. I had a cell stuck in a shutter once that released easily once frozen.

djdister
1-Feb-2019, 20:08
The Tessar lens design show that the front group is made up of two air separated lens elements. Have you tried unscrewing from the back of the front lens group to get at the internal surfaces?

williaty
1-Feb-2019, 20:11
The Tessar lens design show that the front group is made up of two air separated lens elements. Have you tried unscrewing from the back of the front lens group to get at the internal surfaces?

In my older B&L Tessar, that's exactly how it opens up and how I was able to clean the haze out of it. This newer one is constructed differently. The barrel is a single piece from front to back. Nothing wants to screw off, which is why I'm assuming that the front inner ring screws out. Though so far that assumption is failing me.

djdister
1-Feb-2019, 20:14
Can you snap a picture of the back of the front lens group?

John Kasaian
1-Feb-2019, 20:53
I've used a rubber strap wrench with good results in situations like yours. Try the $1.99 cent table at Ace or (as much as I hate to say it) Harbor Freight

Steven Tribe
2-Feb-2019, 03:18
This is an unfortunate back entry job.
The two lenses and spacer have been loaded from the rear and the brass tube has been lathe burnished (Friction causing the brass to become plastic)to create a thin retaining overlap.
This system was cheaper in terms of labour costs than making threads and screw rings. The lenses were never expected to be in use more than a dozen years, or so!

LabRat
2-Feb-2019, 03:37
Let's see a pix of the back c/u, but maybe what Steven said...

Others that I have cleaned unscrew the retainer for the thicker 2nd element and once removed, you can access the 1st element rear surface...

I have seen a description of how to undo a burnished rear seat, as it is thin, but don't remember where, but possible...

These cloud over in time as barometric pressure seeps in a little moisture, that leaves some calcium deposits when the moisture can't leave...

Steve K

Steven Tribe
2-Feb-2019, 07:02
Let's see a pix of the back c/u, but maybe what Steven said...

....

I have seen a description of how to undo a burnished rear seat, as it is thin, but don't remember where,....

Steve K

I am sure I have submitted a description here in connection with RR cells or Pezval achromat. There is an almost a certain garantee that parts of the turned-back edge will break off - but the glass will be OK!

jim10219
6-Feb-2019, 11:47
I've got that exact same lens. I had some fogging between those two elements on mine, and I ran into the same road block you did when I tried to separate them. What I eventually did was dipped a Q-Tip in some solvent and ran that around the edge and let it soak in between the grooves, then it popped right out. It appears the front element is glued down. I can't remember which solvent I used, but it was probably rubbing alcohol or naphtha.

paulbarden
6-Feb-2019, 15:12
I've got that exact same lens. I had some fogging between those two elements on mine, and I ran into the same road block you did when I tried to separate them. What I eventually did was dipped a Q-Tip in some solvent and ran that around the edge and let it soak in between the grooves, then it popped right out. It appears the front element is glued down. I can't remember which solvent I used, but it was probably rubbing alcohol or naphtha.

And if those solvents don't work, try Acetone.

williaty
6-Feb-2019, 20:14
This is an unfortunate back entry job.
The two lenses and spacer have been loaded from the rear and the brass tube has been lathe burnished (Friction causing the brass to become plastic)to create a thin retaining overlap.
This system was cheaper in terms of labour costs than making threads and screw rings. The lenses were never expected to be in use more than a dozen years, or so!

Took me a while to get back to this.

Side image of the lens cell:
https://i.imgur.com/NU1p46b.jpg


I'm trying to upload a video to Youtube that shows the construction much better but it appears that the upload function is currently broken.

williaty
6-Feb-2019, 20:53
Youtube still seems broken but I uploaded it to Gfycat:

https://gfycat.com/AnchoredDisfiguredLamprey

Steven Tribe
7-Feb-2019, 02:30
Super video!
Yes it is mounted from the back. Somewhere underneath the black enamel covering the edge of the rear lens, is a brass edge. Perhaps not burnished, but with the black paint acting as a sealant/glue? This would explain the solvent/push out solution mentioned in one of the last posts. It may have already received this treatment a couple of times, as air spaces do get soiled over time.

I would:

1. find out where the brass ends and the lens begins under the black paint.
2. is there a burnished edge over the glass?
3a. if there is an edge, then mechanically bend back the edge.
3b. if just a friction fit, sealed with paint - go to 4!
4. remove as much of the paint layer as possible mechanically! excess solvents are not good!
5. push the lenses carefully through the rear.

c.d.ewen
7-Feb-2019, 08:59
Steve:

I have to cautiously disagree with you. Here are my two reasons for thinking that the cell comes apart by unscrewing the front: knurling, in my experience, is rarely decorative; it's meant to indicate a part that unscrews. Also, if the rear of the cell is opened, can the front element fit through it?

I have several similar Tessars, and will try to find some time to experiment with them.

Charley

Steven Tribe
7-Feb-2019, 13:04
It is certainly possible, but I have seen knurling that has no function - other than decoration.

The rear lens seems to hang out of the back showing a lot of the lens edge. I assume that the black paint covers almost all of the lens edge and that the brass rim is quite narrow. There is an overlap of this brass which can be seen at the top.
Perhaps an oversize front lens is permanently and separately mounted in the front. But cleaning would be possiblle with just the rear lens out.

c.d.ewen
7-Feb-2019, 20:28
Sorry to report no progress. Spent too much time at the ER getting staples in a minor scalp wound. Maybe tomorrow.

Charley

pepeguitarra
7-Feb-2019, 22:00
There's always a hint - see the knurling on the top of the piece holding the beauty ring in? Get yourself a big rubber stopper or something else to get some friction on that ring and start turning. There are marks in the knurling at 10 and 1 o'clock. I can't tell if they're notches for a lens wrench or not. Check it out. If there are notches at 180 degrees, you've got your answer.

Charley


I have nothing to add here, only that by reading this comment, I remember that I have a Convertible Schneider 50/5.6 -214/12.5 that I could not remove for months. After reading this, I recalled I have some of those rubber stoppers that I used to clean the lenses, and put one around the rim of the front element, and after some hard trying, I was able to unscrew it. It pays to read all the comments. Thanks.

pepeguitarra
7-Feb-2019, 22:03
And if those solvents don't work, try Acetone.

Thanks, Acetone dissolves Crazy Glue. Which I am going to try now. I have a piece or adapter that someone glued (?) on a Copal 1 shutter and I have not been able to remove it, even after dropping some wd40. I now realize that it may have been glued. I will get the acetone to try. Thanks.

Paul Ron
8-Feb-2019, 10:53
acetone or nail polish remover... same stuff, different price.

lacquer thinner works the same if you have some around.

it was common for manufacters to use lacquer as a lock tite.

c.d.ewen
8-Feb-2019, 11:45
No experiments today - out of town.

Crazy glue, will often fracture if frozen. That didn't work when you tried it?

Charley

williaty
8-Feb-2019, 13:06
Well, end of this project :(

There was no way the front lens could come out the back of the cell, so that inner ring had to be a retaining ring. I threw everything I had at it. Heat, cold, solvents, vibration, and finally brute force. I eventually use a jewler's saw to cut slots in the ring for a lens spanner to fit into. Applying an entirely unreasonable amount of force, I got the ring to unscrew about 30 degrees before the lens spanner snapped in half and the shattered stub smashed straight into the center of the lens. So that Tessar is no more.

c.d.ewen
8-Feb-2019, 20:25
The price of a education can be dear.

Charley

pepeguitarra
8-Feb-2019, 20:46
acetone or nail polish remover... same stuff, different price.

lacquer thinner works the same if you have some around.

it was common for manufacters to use lacquer as a lock tite.

Nail polish no longer has acetone on it. I once got my four fingers glued with Loctite while holding a bridge on a guitar that I was gluing. I used nail polish with no avail. Then my neighbors had acetone, acetone did it.

williaty
8-Feb-2019, 20:46
The price of a education can be dear.

Charley

It didn't hurt too bad, actually. It had been sitting on the shelf at the store for years so I was able to bargain them down to $80. For that, I got the lens, lensboard, and a near mint #6 Packard with the rare-as-hens-teeth pneumatic pass through, so I still did ok even with the lens being a write off. I'm glad I didn't have this happen to a more expensive lens though.

pepeguitarra
8-Feb-2019, 20:48
Well, end of this project :(

There was no way the front lens could come out the back of the cell, so that inner ring had to be a retaining ring. I threw everything I had at it. Heat, cold, solvents, vibration, and finally brute force. I eventually use a jewler's saw to cut slots in the ring for a lens spanner to fit into. Applying an entirely unreasonable amount of force, I got the ring to unscrew about 30 degrees before the lens spanner snapped in half and the shattered stub smashed straight into the center of the lens. So that Tessar is no more.

Been there , done that.