Home Brew Tele Pickup Questions

Nomad

Starting to look at getting the bits to make some Tele pickups, and have some questions...

What magnet length(s) for neck and bridge?

Which alnico would be considered 'classic'? (I'm leaning towards A2, but that's only because I like it in the humbuckers in my Lemon Drop.)

Are all of the single coil polepiece style magnets 5mm in diameter? (In other words, will any flatwork suit 5mm magnets from Cermag?)

There seems to be two shapes of cover for the neck pickup...

http://www.axesrus.co.uk/Vintage-Lipstick-Pickup-Cover-Brass-p/hbpc002nick.htm
http://www.axesrus.co.uk/Lipstick-Pickup-Cover-Suitable-for-Fender-Tele-p/hbpc001.htm

Any particular reason to pick one over the other? (Nickel silver is the right material, yes?)

Steel or brass for the plate under the bridge pickup?

What mounting hardware do I need? Thread size?

Anything else I need to consider?

OilCityPickups

Neck 16mm

bridge 17.5mm (not critical) and in some cases staggered.

Alnico 3 or 5

All mags that you will get in this country are 5mm metric ... mags from the States come in .185 and .195 of an inch and must be used in flatwork of that hole diameter. You could get a reamer and use 5mm mags in either US size.

The open sided Tele covers have less metal to block the signal plus let potting wax in better ... and longer legs ... the long skirted ones are similar to the 50s originals.

Baseplates: Steel ... brass doesn't interact properly with the magnets to increase the inductance.

6-32 UNC 

Simples .... squeak

Nomad

Many thanks Ash. I had already ordered today, and got 17.5mm for all magnets (A2,3 and 5, enough for two pickups each, plus some spare A2s for another little idea I have). Got the other bits from Axesrus - it looks like their (overpriced) magnets are also 5mm and their flatwork is cut to match those, so hopefully the fit should be okay. I'll see how the magnet length looks for the neck pickup once they arrive - I dare say I could have the excess poking out the bottom if need be. I also ended up with the full skirted covers (in nickel silver). Noted on the potting (haven't thought that far ahead, but I do have a little hotplate, some pans to make a basic bain-marie, and a pile of paraffin wax). Didn't know the screw size, so I ended up getting robbed. (If this becomes a habit, I'll be buying a bag of the things...)

The bridge pickup flatwork kits say brass for the baseplates, so I might need to sort something out there if they aren't brass plated in reality. Already have a couple of cheapo Tele pickup sets, so there's a possibility of robbing bits if they happen to fit.

The Axesrus stuff should arrive tomorrow, and hopefully the Cermag magnets as well. Only really need the flatwork for now, so that I can work out the geometry of the adapter plate for the winder.

WezV

Nomad said:

 Noted on the potting (haven't thought that far ahead, but I do have a little hotplate, some pans to make a basic bain-marie, and a pile of paraffin wax). 

there is an old article from Lindy Fralin about potting on the stew-mac website.  he suggests a deep fryer can be used, although the suggestion to test it outside until you know it will hold steady at the right temperature is a good one - don't just trust the dial on the front!!

http://www.stewmac.com/How-To/Online_Resources/Pickups_and_Electronics/Wax_potting_pickups.html

and an update

http://www.stewmac.com/How-To/Online_Resources/Pickups_and_Electronics/None_of_your_beeswax_Potting_pickups_with_paraffin_.html

Nomad

Cheers Wez - interesting reading.

Nomad

The flatwork and covers arrived yesterday. Magnets still to come.

The plates for under the bridge pickup are brass, so I'll need to work something out for those, either make or buy steel versions. Not in a rush at the moment for these - planning to do neck pickups for now (bought 2 covers but 4 sets of flatwork so I have a couple to mess up while I learn).

I've been measuring the neck pickup bits, and it looks like the 17.5mm magnets will fit with the bottoms flush with the underside of the lower bit of flatwork. Here's how the geometry looks...

http://i1279.photobucket.com/albums/y521/Nomad_Zamani/Misc/Tele%20Neck%20PU%20Geometry%2001_zpsow9b6zzz.jpg

The flatwork is 2.5mm bottom, 1.5mm top. If I put a top bit into the cover, I get 13mm from the edge of the cover (at the end) to the flatwork. Measuring from the edge of the cover to the inner radius of the cover, I get 15.4mm. Since it's very difficult to measure to the start of the radius, this is approximate, but also means that the inner surface at the magnets is a bit further away than the drawing suggests.

In essence, 15mm of magnet protrudes above the lower flatwork and thus into the cover, and given that the cover bows upwards, there should always be space between the magnet tops and the underside of the cover. The 12.7mm spacing between the two bits of flatwork is based on the fact that metal comes in this as a standard size (1/2"), which makes it easier to make spacers for assembling the bits. The 12.7mm also means that the upper edges at the ends of the flatwork should be just clear of the radius inside the cover.

Should I be aiming to ensure that the end magnets don't make a connection with the cover? I assume there should be clearance, given that the middle magnets will be clear. On the other hand, humbucker magnets and poles are earthed, so maybe it doesn't matter? (Or should they all be earthed or all not earthed?)

OilCityPickups

Don't let the magnets touch the cover top .... in fact tape the tops of them to isolate them ... otherwise you will be making the same mistake Fender used to do ... and in fact still seem to: if there is a crack/fault on the inner insulation of the winding wire  touching one of the magnets it will short to ground and kill the pickup, either now or later ... I had to rewind a Twisted Tele unit that had died because of that a few weeks ago. I lacquer my whole bobbin with magnets once assembled ... to isolate the bare alnico ... then belt and braces ... tape the pole ends. Tele neck pickups are fragile things, and the more you can do to make them 'bugger up proof' the better.

Fender used to hang any extra magnet length out of the bottom of Tele neck units at times in the sixties... and that's still not a bad plan. 

Humbuckers have the core of the bobbin making an electrical insulator ... single coils tend not to.

Nomad

Thanks Ash. I'll do a dry run assembly to see if the magnets contact the cover in any case, but tape on top makes sense, as does lacquering the inside. Any suggestions for lacquer? (I prefer to brush on rather than spray...)

Magnets should arrive from Cermag soon. I emailed them today to see what was happening, and asked about the material - apparently, they're cast and ground rather than sintered.

OilCityPickups

I used to use cellulose sanding sealer brushed on ... nowadays I spray. Give any lacquer plenty of time to cure as otherwise the wire will cut into it as you wind.

I get some magnets from Cermag ... they can be very slow!  Stand by for some winding videos shortly ... 

Nomad

I'll have a look to see what I've got lying around, or try B&Q if I have nothing suitable.

The magnets arrived today. Assembly was pretty straightforward. The holes in the flatwork appear to be slightly tapered - much easier to get the magnets in from one side than the other. With a bit of careful pressing in a vice lined with card, I set them flush with the base and top, and then used a couple of strips of 1/2" brass as spacers while pressing down the top down further with my fingers. The tops of the magnets protruded by 0.5 to 0.77mm (there was variation in the lengths as well - got 17.48 to 17.59). With the cover held in place, there was no continuity between that and the magnets.

Found that Dragon Guitar Parts sell copper plated steel baseplates for the bridge pickups, so I ordered a couple of them and some cotton tape.

Looking forward to seeing the vids.

Nomad

As noted in the winder thread, I've made a test wind to get a feel for the technique. While it's nothing to write home about (let alone stick in a guitar), it does seem to have a convincing DC resistance at 962 ohms for 1611 turns of 42awg wire. I didn't solder - just wrapped the wire at both eyelets, and scraped the lacquer off the loose ends to get the probes on. That was without lacquering the bobbin. Had a mooch round B&Q but didn't see anything convincing. I have a little pot of glossy black acrylic paint somewhere (hobby/crafts stuff), so I might give that a try once I get the wire off.

Things I learned...

• Threading the wire through the eyelets is fiddly.
• I should have cut off the excess before I started winding - it worked its way around from under the flatwork and got trapped under the winds.
• When coming to the end, work the turns back towards the bottom flatwork to ensure the wire doesn't span a gap and thus become vulnerable.
• I need to practice more with tension.
• Need to think more about scatter patterns and evenness (or not) of fill as it builds up.
  
  

Going back to the potting... In the two articles linked to by Wez, Fralin at first uses an 80/20 paraffin/beeswax blend, but later drops the beeswax because it affected the tone in some way. How could the type of wax affect the tone? I'd have thought the electrical characteristics and magnets would be the primary factors, and maybe whether the pickup was potted or not. If beeswax has better dimensional stability in thermal variation, I'd be tempted to use that 100%. Is there any reason not to?

Nomad

Just did the first proper wind, and it seemed to go well. This has the magnets north up, and wound anti-clockwise looking at the top of the pickup. 42awg wire, 8000 turns, and it measures 5.6K - does that sound about right?

I found the acrylic hobby paint, and that seems fine - dry in the time it takes me to clean the brush (in water) and have a cig while I leave the assembly under a desk lamp to help the paint dry. I went for a more even fill than I did with the test wind, moving more gradually across the width, and sometimes pausing in certain areas to build it up a bit. It's quite hard to see what's going on when it's spinning, especially how much room is left on the bobbin, so I stopped the winder 2 or 3 times to get a better look. It looks pretty even to me, and I notice that it bulges a little in the middle of the wind. I wasn't sure whether I would be able to get 8000 turns on.

The finger pinch tensioner method was a bit uncomfortable after a while - I might look into making some sort of clip thing that I can hold and wiggle. The tension seems fine, though - solid at the ends, but still a bit of give in the middle of the span either side.

I've still to add the hookup wire, but not sure how much yet - I guess I need to look inside the guitar for that. Also need to get the end holes threaded for the fixings. The plan is to do a before and after recording, so I need to pick an amp and set things up for that before I start messing about with pickup changes and soldering on hookup wire. Once that's done, I can do some low volume (house level) testing while I think about potting and fitting the cover.

Anyway, here are some photos...

http://i1279.photobucket.com/albums/y521/Nomad_Zamani/Pickup%20Winder/PU%20TN01%2001_zpsb8ukcmhl.jpg

Well filled. I don't think there's scope to put any more on, given that tape has to go on as well.

http://i1279.photobucket.com/albums/y521/Nomad_Zamani/Pickup%20Winder/PU%20TN01%2002_zpsbbfelfah.jpg

Can see the slight bulge in the middle of the wind here.

http://i1279.photobucket.com/albums/y521/Nomad_Zamani/Pickup%20Winder/PU%20TN01%2003_zpsnrwscqop.jpg

Gratuitous pretty picture.