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I decided before Christmas I wanted to have a go at making my own magnetic pickups, and put it on my to-do list for the new year. I studied this guide http://www.instructables.com/id/Make-A-Guitar-Pickup/ extensively and ended up taking inspiration from a few other sources to come up with a design, here is the process:
I ordered a 500g spool of 42awg (0.063mm) copper magnet wire from Brocott's (UK supplier) and a couple of packs of alnico 5 rod magnets (5x19mm) on eBay. I had some 3mm sheets of sapele so I figured I would use this for the bobbins.
These were the first 2 bobbins I finished, I fixed the magnets flush with the top and bottom with a dab of superglue and drilled 2 holes for the start and end of the wire. It is really important to sand the inner surfaces of the bobbins completely smooth and free of any tiny burrs as the wire will get caught. Best case scenario you'll have to unwind several hundred turns, worse case the wire will break and you'll have to start over.
This is the winding jig I made. I did try a sewing machine first but I felt that I didn't have enough control. This is just a hand-cranked drill clamped to a desk, with a block of wood fixed to a dill bit. I attached the bobbin with an adhesive pad. One turn of the handle is about 4.2 turns of the bobbin, so I would do 50 turns, check for any tangle or loose winds, then do another 50 and mark a tally. When I had done 19 x 100 revolutions of the handle, I had roughly 8000 turns on the bobbin. This took about 30 minutes altogether.
I then decided to make a hole in the soundboard of one of my guitars to check for the fit. I use a neck-through design so I also needed to chisel out a recess for the bottom of the pickup to sit in.
I used a drill to start the hole, then fed a coping saw through to cut it out, then sanded etc. I then realised I hadn't thought of how to mount the pickup, and after looking at pages of pickups on Google images, I decided to start over and go for a top-mounting design. (Thanks to Mr. Crocker - an endless source of inspiration!)
These were mark 2. I made the tops of the bobbins larger than the bottom, so I could screw them into the soundboard through the top, covering up the hole for aesthetic and acoustic reasons. I also replaced the holes for the start and ends of the coil with small screws. I used steel screws for these but I do not recommend it - it is very tricky to solder onto them - as you can see:
Hmmm... not looking too great. Soldering was very difficult as I needed to melt off the enamel coating on the copper wire before the solder would stick. However I checked the connections by attaching a jack and plugging it in and it did work! Next step was potting.
This is a double boiler I constructed to melt the wax. I put about 600g of parrafin wax pellets into a kilner jar, placed a block of wood underneath so the jar was not in contact with the heat source and lashed the top of the jar to the sides of the pan with rubber bands. I filled with water up to about 1" from the top level of the wax and used a meat thermometer to gauge the temperature (which needs to be about 65c). I should add that I have an electric hob, and I think this process would be quite dangerous with an open flame. (This is so far the only advantage to an electric oven I have ever found).
Once the wax had all melted, I wrapped the lead wires from the pickup around a screwdriver and rested it on top of the jar, so the pickup was suspended in the middle, not touching the sides. The idea here is to wait until the bubbles stop rising and the coil will be saturated. I should add that the wood I used also took in wax - and bubbles came off that too. I have it about 20 minutes, took it out, wiped the excess from the bobbin and let it cool. I then wrapped round some PTFE plumbers' tape to protect the coil.
Then it was time to wire it up and put it in the guitar:
I then strung it up and plugged it in.
Hmm... not much volume, and lots of buzzing. I replaced the bridge with a pencil, to make it much lower, and the sound was louder - the pickup was too far from the strings. I also had not grounded the strings (which is a whole other problem as my bridge and tailpiece are both wood. Back to the drawing board again!
As you can see from Ted's diagram, the ground wire needs to connect the pot with the strings. I am planning to replace my wooden tailpiece with a metal one.
This is the new pickup I made last night. As you can see the top of the bobbin is much thicker, 6mm this time (an offcut from a sapele fretboard). The termination screws are now brass, so will be easier to solder. I also used a craft knife this time to scrape off the enamel coating, so soldering should be much easier. My next step is to pot it in wax and then wrap it with some copper foil tape, which just arrived yesterday. I will solder a wire from the ground on the pickup to the outside of the copper tape (thanks Bob Harrison for this tip). This combined with grounding the strings should have much better results, so fingers crossed.
I'll let you know how it goes!
[Part 2 here now: http://www.cigarboxnation.com/profiles/blogs/my-continued-adventure...]