Olympus OM-1 prism rot

[baachitraka]

Is OM-1 only suffering from this dreaded prism rot or is it common for all Olympus OM (analog) cameras?

 

[faberryman]

It is not really prism rot. It is the foam between the prism and the top cover.

 

[baachitraka]

yes. But it renders the prism unusable I think.

 

[wiltw]

Deterioration of the foam affects OM-1 and OM-2 only, that I know of.

 

[M-88]

I've interacted with dozens of OM machines in the past. OM-1, 2 and their "n" subversions are affected by the issue. Others are not, because later models have vinyl-like plastic instead of the foam above the prism, which obviously does not deteriorate with age.

The top cover is fairly easy to remove (repair manuals are widely available) and the prism silvering can be repaired, if it's worth to you. Replacing the prism is all too easy as well. Just keep in mind that OM-1 and OM-2 have slightly larger prisms than OM-2S and OM-4, so pick an appropriate donor. Not sure if OM-10/20 prisms are compatible, I have never tried.

 

[Michael L.]

yes. But it renders the prism unusable I think.

Hardly. The degraded foam is easily removable, and after that the prism is still completely serviceable.
Visit these sites for help:
http://olympus.dementix.org/Hardware/tutorials/OM-1CoverRemoval/index.html and http://olympus.dementix.org/Hardware/tutorials/FoamRemoval/index.html

 

[baachitraka]

Thanks. I just can't get over from this Oly addiction.

 

[Ap507b]

Read somewhere there was a period in the OM1 MD run where they didn't put the seals in but then went back to fitting them. My MD & N when i bought them were clear of rot. Sent both of for CLA's & was told that the foam was removed just in time from the N. Same with the OM2N.

Bought an early OM1 last month as a restoration project . Made between 72 & 74 i think as no motor drive socket. Jammed film advance & mirror stuck up & the foam has damaged the prism. Have read that an OM10 prism is a straight swap for an OM1 so a broken OM10 as a donor. Will be sending it all off to Miles Whitehead next month for him to work his magic on it & bring it back to life.

 

[CMoore]

Hardly. The degraded foam is easily removable, and after that the prism is still completely serviceable.
Visit these sites for help:
http://olympus.dementix.org/Hardware/tutorials/OM-1CoverRemoval/index.html and http://olympus.dementix.org/Hardware/tutorials/FoamRemoval/index.html

Wow.....the camera in that link is an M-1.
How many of those did Olympus actually make.?

 

[darinwc]

If you can find a dead om10 for cheap, the prism is a direct fit and there is no foam.

 

[Quendil]

I've swapped prisms in an OM1 and OM2 and its fairly easy. You can use OM10 or OM20 ones I have also managed to pick up cheap OM1 and OM2 for spares. If its just the foam that has gone it can usually be cleaned off the prism, if the prism is desilvering you ned to swap it out. This blog has a strip down of the OM1

https://simonhawketts.co.uk/2016/07/16/olympus-om-1n-strip-down/
https://simonhawketts.co.uk/2016/07/17/olympus-om-1n-reassembly/

Service Manuals http://olympus.dementix.org/Hardware/

I have far too many OM cameras and am completely addicted

 

[John51]

I have far too many OM cameras and am completely addicted

Time to stop acquiring OM bodies and start collecting the rest of the system.

 

[baachitraka]

Yes, 21mm and 100mm f/2.8 are in the wish list and I hope I will find a black OM-1 body for an affordable price.

- 28mm f/3.5, 50mm f/1.8, 85mm f/2 (100mm f/2.8) and 135mm f/2.8 (135mm f/3.5) must be in the starter pack. Then comes wides and teles...

Shot with 135mm f/2.8. APX 100 in PC-TEA (great keeper of hightlights) and I think printed on MCC 110.

 

[wiltw]

Wow.....the camera in that link is an M-1.
How many of those did Olympus actually make.?

Supposedly Olympus had stated that 52000 M-1 bodies had been produced. I am the proud owner of one of them, with two lenses with the 'M system' engraving identifications (not the 'OM system' lens designation.

 

[CMoore]

I did not realize they made that many.
I am happier with my OM-1n ....... but the M-1 certainly fetches a premium price on Ebay/Etc

 

[plummerl]

Hardly. The degraded foam is easily removable, and after that the prism is still completely serviceable.
Visit these sites for help:
http://olympus.dementix.org/Hardware/tutorials/OM-1CoverRemoval/index.html and http://olympus.dementix.org/Hardware/tutorials/FoamRemoval/index.html

Maybe read the second link that you provided. I had the foam rot in my original OM-1 and true, it does not render the prism completely unusable, but the rot does degrade the silvering at the point of the rot(s). This causes black spots to appear in the viewfinder and is definitely somewhat distracting, not to mention being unable to see anything at the rot location. As others point out, I picked up an OM-10 parts only camera and used the prism as a transplant. Exact match.

 

[Quendil]

I have far too many OM cameras and am completely addicted

Time to stop acquiring OM bodies and start collecting the rest of the system.

Already Started

 

[crumbo]

On many early OM-1 and OM-2 bodies, the gap between the eyepiece and prism was covered by a strip of the same foam material used around the back cover, and other places on OM bodies for light control (i.e., around the back cover and elsewhere) and for impact absorption (where the mirror hits when it goes up). After may years, it began to revert to it's petroleum byproduct origins -- in other words, it turned into gooey, slimy, icky stuff! (Many later models of the 1 and 2 covered this gap with different covers -- usually plastic shields that doubled as protection of the prism from the retaining spring that held it in place, and so this is not a universal problem.)

The foam against the prism eventually begins to dissolve the paint and silver coating of the prism.

It is possible to remove the prism, clean off the damaged "goo", and buff the glass clean (a cotton wheel on a Dremel-like tool works well, especially when coated with jewelers rouge). When reinstalled and the top cover replaced, the transition from bare glass to mirrored glass is usually hardly noticeable. But for purists/perfectionists, you can harvest donor prisms from any OM-1, 1n, 2, 2n, 10, 10Q, F, G, 20, and 30 -- the part is the same on all these models. I am not sure of the OM-2000 (different part number), or the OM-PC/40. The OM-2s, 3, 3T, 4, and 4T all used different prisms.