jamiegramo wrote: ↑Tue Mar 09, 2021 11:59 am If the problem is the diaphragm this could be because celluloid becomes hard and brittle over time. It’s an inevitable problem with most early plastics that they will deteriorate. If the future looks bleak for humanity it is also bleak for the Cliftophone. Perhaps they sounded really good when new, after all Brunswick bought them out.
I am wondering if you could apply a thin coat of linseed or mineral oil to the celluloid, this could then be lightly over coated with a small amount of alcohol (methylated spirit/denatured alcohol). The idea is to penetrate the celluloid and soften it so that it goes back to being more compliant for sound reproduction. Alcohol is an ingredient of celluloid but there is a danger it could melt the celluloid. I guess you could test the edge or I’ve got some old bits of celluloid I could dig out and test with meths to see how it reacts. This is only an idea...
This assumes it’s not the gaskets...
Celluloid goes bad when its camphor content evaporates, so solvents or oils wouldn't help as much.