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Need help: decementing repair on a M2


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My 1966 M2 suffer from decementation since a few years (since has badly fall off on the rewind knob). :(

 

-Silvering is 2/3 yellow now and decementation increase rapidly ( was 1/2 two month ago), as I'm afraid of the cost of repair in front of the actual value of my M2, I wondered if it's possible to put M4 or M5 prism from a junk...

... or repair it by myself (total decementation-> cleaning with alcohol-> reduce oxydation with (soft) phosphoric acid-> cement with new Uv glue... / or buy a Canon RT, Cut the mirror and cement it between the two prismes with Uv glue after elimination of the old silvering) ????

 

I'd appreciate to know your experiences and knowledge about that (even real cost of repair or spare parts).

 

Thanks,

Bertrand.

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I have done this on and SEI spot photometer prism before, I soaked it for days in acetone to seperate it, dont apply force, just wait. Because I didn't want the problem of re silvering the spot I took great care not to touch it with anything other than acetone. As you suggest I glued it back together with UV stuff, simply held it togethrt in the sunshine for a few minutes.

 

You will find the black paint on the outside comes off, this is an anti reflecting coating, Humbrol enamel is a good substitute. It is probably worth removing some paint over the join and drawing a few pencil lines (they won't dissolve in acetone) across the join to aid reassembly. As to the corroded silvering it may look a lot better after doing this without the need to re-do.

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Many thanks for your help alifie... :)

 

- I may try with the acetone, I don't think there would be any risk for the semi-reflexive coating

 

- For the black matting, I tried with tar on a lens some time ago: perfect dark black but very high temperature is forbidden: behind chrome lenses and cameras only.

 

- I'm not sure for semi aluminized film. I bet it wouldn't stay plan if cemented between 2 prismes or there is a big risk of Newtons rings.

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  • 1 month later...

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Hi Guys,

CRR in Luton UK can offer a resilvering solution for about £150 which is highly recommended. I have had this also done by Malcolm Taylor again in the UK, again highly recommended. I had a prism resilvered for about £25 again available in the UK. I'm sure there are other available solutions across other continents, once you have lost the origin coating though just recementing is not an option. I have just repaired my M4 in this way and with care is quite a viable procedure, as stated care with the mirror surface will be repayed with success. UV curing optical adhesive is readily available at low prices.

 

Best,

 

normclarke.

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