Does anyone repair L12A1 7X42 Avimo Prismatic Binoculars?

[Vincent]

I think the prism assemblies have come loose and are rattling around inside.

Is it a repair I could make?

Information

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[Peter Laidler]

The real problem is that you could get inside and tighten the prism - or whatever it is that is loose but once you have done it, they will need collimating. And THAT is the difficult thing to do with L11's and 12's. That's because in those, you have to use multiple eccentric rings to collimate two separate prismatic telescopes whereas with the old No2's and 5's you rotate a simple(?) prism on one or both and this prism is the actual objective lens. The L12 binos have a special collimator........

I think that I might have the parts list so you can see your way. But don't hold your breath.........

[Flying10uk]

Does this model of binocular have a bonded prism and if so is it not likely that that adhesive has failed? A few years ago I paid an "expert" to refurbish a pair of Barr & Stroud 7x50 Naval binoculars for me but I regretted it because they came back with one side showing spotted vision. When I complained about this I was told that special jigs were required to re-glue the prism which were no longer available and so I would have to accept it as it is.

[bigduke6]

A few years ago I paid an "expert" to refurbish a pair of Barr & Stroud 7x50 Naval binoculars for me but I regretted it because they came back with one side showing spotted vision. When I complained about this I was told that special jigs were required to re-glue the prism which were no longer available and so I would have to accept it as it is.

A jig can be made very easy and doesn't have to be a tool room example, although not for a Barr & Stroud the pic should give an idea, as Peter said using balsam you can redo till the cows come home.......

A very simple jig below, Heath Robinson yes but does the job....




A link below is a repair to Binocular Prismatic No5 may be of interest to some, includes the home made Jig above.

https://www.milsurps.com/showthread.php?t=53576

[Vincent]

The real problem is that you could get inside and tighten the prism - or whatever it is that is loose but once you have done it, they will need collimating. And THAT is the difficult thing to do with L11's and 12's. That's because in those, you have to use multiple eccentric rings to collimate two separate prismatic telescopes whereas with the old No2's and 5's you rotate a simple(?) prism on one or both and this prism is the actual objective lens. The L12 binos have a special collimator........

I think that I might have the parts list so you can see your way. But don't hold your breath.........

Thank you, Peter. Obviously not something I can do then.

They worked for 37 years. That’s a good run in my book.

Does this model of binocular have a bonded prism and if so is it not likely that that adhesive has failed?

I have been reading and that is probably the case.

The good news is I found a pair for sale and they are on the way.

I would still really like to have these repaired if it’s possible.

[Peter Laidler]

Nope, the bonded prism was the preserve of the No5 7x 50 binos. There was a jig to replace the lens onto the prism but if your repairer had simply looked at the other side and judged the positioning reasonably accurately using balsam instead of UV fix, then any small discrepancy could have been rectified using the prismatic OG lenses. UV fix means that the lens is stuck to the prism for good...... fault an' all!

[Peter Laidler]

Nope, can't find a parts list for the old L11 and 12 binos but did find others. But internally they're not complicated. In fact they're really two slimmed down SUIT or SUSAT sights joined together

[Vincent]

Thanks for looking Peter.

You said they are like two sights joined together. Does that mean I can replace the left side with the left side from another pair?

[Peter Laidler]

Yep. While the sides are handed the internals are identical except for the graticle pattern cemented within the field lens. Just beware of that if you're dealing with L12's. L11's are opbserving binos as opposed to spotting binos so they don't have a graticle

[Vincent]

Thanks Peter. I will give it a try.