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 Post subject: Duplex IIi problem--delamination?
PostPosted: Tue Nov 13, 2018 1:22 am 
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Hi everyone ! I recently snagged a vintage maxilab for ehat i think was a good price. Everything seems to be working, with only a few missing bits and an apparently dead battery. I am suoer impressed with it overall, but the one bummer is the duplex III seems to be nonworking. I will not claim to be a master of the refractometer, but I can easily get a reading with my cheap Chinese one but can't on the duplex. Upon examination it looks like the hemicylinder has some delamination(?) Of some sort:
Image
I know Jeff wildman has a reputation for replacing duplex II hemicylinders, but I was wondering if this is a standard problem or if something else is wrong.
Thanks!

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 Post subject: Re: Duplex IIi problem--delamination?
PostPosted: Wed Nov 14, 2018 1:20 pm 
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That delamination is not causing any problem. It is merely a delamination of some cement on a bridge underneath the slot in the prism. I have one with a similar spot. The slot is cut to make it easier to only see part of the illumination going up to the surface. Since it's there they made a support bridge too.

The Duplex III is a little harder to use. The surface of that one looks fine and I don't see any cracks. They are harder to use because of their more compact and simpler optical system. In a regular duplex the optical system on both sides of the prism is longer and narrower field of view which makes it easier to "find" the shadow edge. That refractometer probably works. Just keep trying and you will find it (the shadow edge). The delamination is not in the image path/aperture. Try using a yellow filter/LED / or heaven forfend an actual sodium lamp. You are someone that should be using the latter anyway.

If you set your Duplex III next to a Duplex II you will see the prism is identical. The three sides around it have all been truncated to make it smaller.


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 Post subject: Re: Duplex IIi problem--delamination?
PostPosted: Wed Nov 14, 2018 3:43 pm 
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Ah, that's good to hear! I've never used a Duplex before, just cheap Chinese ones. I tried it with the maxilab's built-in fiber optic light and with the sodium filter and had no luck either way, but maybe I didn't have the stone positioned right. I'll retry with something bigger and report back.

edit: huge thanks! I was positioning the stone wrong--when I finally hit the right spot it showed up beautifully. I feel a bit dumb but it's overwhelmed by how pleased I am that the refractometer is working. Thanks once again for your help!

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