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Fresnel lens back to front


nick123

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Maybe this should be obvious or doesn't matter, but one of the patt 123's I'm overhauling has the stepped face of the lens facing in instead of out as usual, and I'm wondering why. I'm thinking perhaps that it was replaced or removed at some point and whoever put it back simply got it wrong, but wondered if there could be more to it.
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Nope - whip it out and put it back in the other way.

 

Thanks. I expect people have found worse, but the amount of dust in these units is pretty terrible. Lamps with pools of dust on them, the steps of the wrong way round lens choked with dust, the inside and reflectors coated with dust. I recokon at least a decade of neglect and possibly rather more.

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Nope - whip it out and put it back in the other way.

 

Thanks. I expect people have found worse, but the amount of dust in these units is pretty terrible. Lamps with pools of dust on them, the steps of the wrong way round lens choked with dust, the inside and reflectors coated with dust. I recokon at least a decade of neglect and possibly rather more.

 

 

Dust and dirt is the most common cause of low output from old fixtures, a good dust out, polish the reflector with duraglit (brasso) and fit a halogen lamp, you will find the 123s have a new lease of life, I can confirm that Strand never fitted the lenses back to front, someone was probably trying something out but what I don't know!!, you may find the lenses have a slight yellow cast to them that can also slightly reduce the light output, this is caused by the mesothorium or radium (depending on the age and glass maker, more likely mesothorium in stage lantern glass) that is an ingredient of optical glass decaying, forming oxides if the uranium series (this is used to make yellow dyes and paints) , it can be eliminated by leaving the lenses on white paper in bright sunlight for a week or so.

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