This wound up on the work bench a few weeks ago ... so I thought I'd share!
It's an old (probably 1960s) Hoyer brand mandolin pickup ... and very dead. This is interesting as it pretty much apes the construction of early Hofner six string 'add on' pickups ... and was going to be equally a bitch to rewind.
Inside you see a ceramic bar magnet ... er well ... a well broken up one that was clearly like that from day one. With ceramics (and rubberised ceramic) it doesn't matter if the magnet is broken, so long as all the parts are held firmly in the right polarity.
There is a steel base plate that transfers the magnetic field to the centre block that takes the four pole screws. In this case the pole screws really only hold the cover on and are not adjustable. Around the core you see a soft, squishy bag of wire that is the 'air coil'. With air coils there is no bobbin used, and the coil is wound around a removable former.
As there are no air coil formers made these days, we laser cut our own (see below) and pretty much have to do that for every different size of air coil we get to repair!
The time taken to CAD design and cut the former is a pain, as is making it so that tape can be passed through slots to secure the coil before removing it.
However the result is a working air coil pickup once more :-)
For those who missed how we make air coil formers ... take a look at our previous Burns Rewind thread
Air coils do have a particular set of tonal characteristics ... and we are thinking of adding a couple of air coil designs to our lineup in future.
Professional pickup winder, horse-testpilot and recovering Chocolate Hobnob addict.
Formerly TheGuitarWeasel ... Oil City Pickups
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