Restoration of Antique Headphones with Broken Electronics

In this video I'm restoring a pair of antique German headphones. I've found these headphones at an online auction for $30 and I thought they look pretty cool for a restoration project.
Unfortunately they didn't work anymore. I measured the coils and three of the four were broken. That fact put this little project to a whole new challenge. It required a ton of research to completely understanding every single detail of its function to remake the coils and such. After some trial and error I managed to remake the broken bobbins and rewind the coils. The tricky part was that both coils are connected with each other at the beginning of the windings in the core. I had to make a special jig, so I could clamp both coils when winding the second one.
The original paint had some kind of a structure in it. It was black matte with some kind of a hammertone pattern. Unfortunately I was not able to find such paint, so I went with regular black matte. To not loose the were fine writings and logo I only applied a very thin layer of primer and coat.
The Bakelite pieces just required some wet sanding and a good polish and they looked like new again. Old Bakelite might contain asbestos, that's why I wet sanded them so there won't be any sanding dust.
I cleaned the membranes with scotch bright after a 24h bath in rust remover. To get rid of the pitting I sanded it with 240 grit sandpaper. I was already down to 0.13mm from 0.2mm thickness, but there was still pitting visible and I just sanded one side. To get the best possible sound at the end I decided to remake both membranes with new 0.2mm steel foil. To match the original membranes I also painted the center black matte.
I nickel plated all the screws and the two brackets like they were originally. The brackets were a little bit weird, because they were two identical ones instead of pair of mirrored ones. I fixed that pretty easy by just bending the shaft on one ion the opposite direction.
I was very lucky that the cable was in nearly perfect condition. It had absolutely no visible damage or fraying, just lost a bit of color. I just had to shorten them. Todays headphones all work with AC, these however back then worked with DC. Therefore the polarity matters. I also marked all endings of the cable with red and black threads, so did I made a red and black plastic cover for the plugs.
In the end I'm very happy how these headphones have turned out. The color combination of the black matte with the shiny black Backelite parts look very classy together with the shiny nickel plated parts and the crispy clean looking knurling is the cherry on top.

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