Meltrope III Diaphragm attachment to needle bar

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Inigo
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Re: Meltrope III Diaphragm attachment to needle bar

Post by Inigo »

And in the exhibition, the circle or cone of red hard wax.... Which size? I'm tempted to try that... My first homemade soundbox had a cardboard (thin and stiff) diaphragm. My needlebar was made from a lady's hairpin, and the sealing with the diaphragm was done by simply inserting the needlebar end into the center of the diaphragm and sealing with that red hard wax. It sounded fairly well, and lately I've been tempted to repeat that design, replicating my first own child's Gramophone for the sake of posterity...
Inigo

old country chemist
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Re: Meltrope III Diaphragm attachment to needle bar

Post by old country chemist »

Greetings all Talking of sealant for the stylus bar to diaphragm. Well, I do not know if he has mentioned it on the forum, "epigramophone" has been using PVA glue to bind the two to make a good airtight seal. I have been using PVA since he suggested it some years ago, and I believe it is a very worthy item in gramophone re-builds. I use one or two drops on each side of the diaphragm, and let it dry for several hours, depending on temperature. It really is so much better than the sealant that H.M.V. used, which was resin powder and beeswax mixed together. If a soundbox has to be dismantled, then a few drops of hot water on the PVA holding the diaphragm to the stlyus bar will soften it for it to be scraped away enough for the tiny diaphragm screw to be unscrewed. I know it is not an original item-but who cares!! It does the job so well.
I also agree with loading the centre of the diaphragm with more sealant than is normally required. One has to try it to notice the difference!

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Inigo
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Re: Meltrope III Diaphragm attachment to needle bar

Post by Inigo »

Interesting.
I've been using PVA (or Elmer's glue for our American friends) in soundboxes, and I find it marvelous. And it's easy to remove, even dry. I've used it as sealant, but never thought of using it at the center of the diaphragm.
Today I've bought a bar of red Chinese hard wax to try it on my experimental exhibition sbx. I'm impatient to apply it and watch the results...
Inigo

leels1
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Re: Meltrope III Diaphragm attachment to needle bar

Post by leels1 »

Old thread, but for what it’s worth I have successfully managed to araldite the needle bar onto the diaphragm from the front side. In this case it didn’t need the back “washer” as the araldite has provided an airtight seal ok.

As has been mentioned, positioning the diaphragm centrally in the back, then lining it all up works best. Those needle bars seem really fragile and too much bending will break them.

This also has the advantage of not putting too much pressure on the needle bar/ diaphragm so it can all move freely.

Perhaps it seems to have lost some of the deeper bass tones, but all the Meltrope IIIs I’ve got sound different. To my untrained ears I know what I like, but not what it “should” sound like.

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