Minolta XD-11 (XD-7) pentaprism removal

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md_

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I've got a new-to-me XD-7. Unfortunately, it has a bit of dirt on top of the pentaprism, right along the top vertex (as best as I can tell). I've already removed the focusing screen (scratching it a bit in the process!) and cleaned the mirror and focusing screen and bottom of the prism, but I'm not sure how to get at the top.

The best documentation of the XD-7 layout I can find is this video, which unfortunately does not show pentaprism removal.

Anyone know how to do this?

Thanks!
 

shutterfinger

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md_

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Thanks. Yeah, I found this manual before. It's not clear to me if the pentaprism actually comes out from the top once the top of the body is removed or somehow from beneath through the lens opening (once the lens collar and mirror are removed). I don't think the latter, though--after removing the focusing screen, I don't see any likely way to remove the prism.

I'm not too worried about taking off the top of the body to check it out, but I'd be pretty hesitant to take out the flex circuits based on this manual. Seems like a real nightmare. Shame, though the smudging is certainly not the end of the world.

Thanks anyway.
 

AgX

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Dirt at the top of the prism would not be visible as these prisms are coated with a reflective layer. But fixtures can corrode these layers or they may have corroded out of themselves. In any case nothing to be repaired by a basic camera tinkerer, aside of exchanging the prism.


Cleaning the mirror: dirt on the mirror will not show up as such in the finder.
 
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md_

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This is definitely somewhere in/on the prism or viewfinder itself; it's not on the focusing screen or mirror in any event. It looks like a double line of dark dots, mirrored, running down the center of the field of view.

Yes, I would imagine it's damage to the reflective layer, since dirt on the outside of it would not be visible. That's a good point. :smile:
 

John Koehrer

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The prism is removed from the top. It's very likely that it's going to have old & sticky foam around the edges where
it's fitted into the frame. If you want to give it a shot, there's the old gum wrapper on top of the prism method
Does gum still come with metalized wrappers? If you try this,you can check the effectiveness by setting the foil in place
and putting the prism back before you make it permanent. If it works, tape will hold the foil in place.
Keep on mind the metal side is conductive......................A donor body with a good prism would be better.
 

Kino

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I repaired a bad prism with Krylon, "Mirror in a Can" spray paint. You have to remove all the deteriorated silver very carefully and don't scratch the glass. Five very light coats of this paint, wait until totally dry and a few coats of glossy black. Very hard to tell it was ever damaged...
 

AgX

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Interesting, I did not think of such makeshift mirror coating repair so far. I actually got one can of chromium effect paint spray in house. Never used it, but shall test it on a piece of glass.

The "correct" way would be to coat it oneself by means of a silver-solution or give it to an optical workshop with an evaporation coating facility.
 

Kino

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Interesting, I did not think of such makeshift mirror coating repair so far. I actually got one can of chromium effect paint spray in house. Never used it, but shall test it on a piece of glass.

The "correct" way would be to coat it oneself by means of a silver-solution or give it to an optical workshop with an evaporation coating facility.

Yes, if the camera was worth the expense, it would be the proper way to do it. A grungy K1000 is not worth the expense...
 

David Lyga

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Some of these electronic Minoltas allow for removing the bottom Fresnel to clean the debris. From the mount area, you gently lift (up or out) a tiny metal flat spring that releases the Fresnel. Different models do this differently, but some do not have this advantage. - David Lyga
 

neilt3

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Dirt at the top of the prism would not be visible as these prisms are coated with a reflective layer. But fixtures can corrode these layers or they may have corroded out of themselves. In any case nothing to be repaired by a basic camera tinkerer, aside of exchanging the prism.


.

I have a Bronica ETRSi Prism finder that had this problem .
Looking threw the viewfinder you would have said that there was a streak of black dirt inside it , very distracting .
Being a solid lump of glass it's clearly not inside it .
Having dismantled it to remove the prism it was clear that the foam/rubber on the top of it to provide a cushion between the glass and the metal body had degraded to a gooey mess and damaged some of the silver/aluminium coating from the ridge of the prism about 1/8" either side and about 1" long .

Not prepared to send a £20 finder to be re-silvered I tried a D.I.Y fix .
I bought a metallic silver marker pen ( like this ; https://www.ebay.co.uk/itm/7F84-Pai...hash=item3fa9568347:m:mSx7a1wbfOzudBx9aG0wKtw ) and recoated the missing bit .

Despite it not being reflective , the repair made the prism seem as good as new .
As a black streak it was very noticeable and distracting , now you don't notice it .
As it was a small percentage of the viewfinder , and being for medium format film rather than 35mm I think this helps .

Also , being on the ridge and not in the middle of a flat area probably made this type of repair possible as it would be on the edge of the reflected image .
Had it been on a flat surface , that part of the image would never get to your eye and re-silvering ( or replacing the prism ) would be the only option .



This is definitely somewhere in/on the prism or viewfinder itself; it's not on the focusing screen or mirror in any event. It looks like a double line of dark dots, mirrored, running down the center of the field of view.

Yes, I would imagine it's damage to the reflective layer, since dirt on the outside of it would not be visible. That's a good point. :smile:

See above .
Most likely the same issue I had with the Bronica viewfinder .
 
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