Well Ben you've asked a question about one of the most difficult pickups to make from scratch. The original Burns Tri-Sonic pickups were an air coil with a ceramic magnet. The coils are wound on a collapsible former. Once the coil is wound to spec, the former is collapsed from the inside, and the coil is taped completely. Then its put into the cover with the magnet, and then the whole thing is epoxied so it won't be microphonic. The coil is very thin top to bottom, and there is no bobbin.
The new Burns Tri-Sonics aren't made the same, and so don't sound the same either. The only one I know of that makes the Tri-Sonics correctly is Adeson in the UK, and I have a set of his pickups. I don't have anything to pu them in yet, but I will. He uses the actual equipment from the 50's that Burns made their pickups on, and uses the same methods to make them. The pickups are very reasonably priced too. Check out his site and email him about it...he's very friendly.
Here's some stuff he told me about their pickups in an email.
Regarding the coils - all early European pickups (Hofner / Framus / Hoyer etc..) were built this way. The coil is wound on a removeable chassis - and then completely wrapped in a special armature winding tape (takes ages to learn this - they are ridiculously delicate!). The whole thing is pulled tight - just like lacing up your boots. The magnets are vintage ceramic (similar to Alnico 2). They have been out of production since the early seventies - I have to have them custom made - and they cost a fortune!!! The coils are then placed arround the bar magnets (the holes in the chrome top covers are purely aesthetic). The whole thing is then glued solid to prevent the brass top covers from causing howling. This is exactly how they were made 40 years ago - and they sound great!!!
Many thanks for your enquiry. Our pickups are identical re-creations of Tri-sonic pickups built between 1960-65. We use the exact build methods and original components - they are even wound on the original late 50's Burns winding machine, making them the most accurate version of this classic pickup - period!!!!! We can easily supply a hotter bridge pickup, however on Brians guitar the "hot" pickup was in the middle position. Most Red Special experts want - neck pickup approx 6.5k, middle approx 6.9k, and bridge approx 6.7k. Apparently these figures are based on Greg Fryers restoration of Brians original guitar. Regarding pots and caps, Brian's were Omeg 220k log B pots with a .022cap, although Burns originally used 500k pots in the 60's.
For the whole set of Tri-sonics from Adeson, it was less than $200 with shipping though this was about 2 years ago. Hope this info was helpful to you?