hand wound pickup question

[mike ryman]

Hello. I have built an electric guitar. I have done all of it myself so far. Body, neck, fretboard, everything myself by hand. I put the pickups in and wired it all up only to find 1 wire in the bundles touched ground and blew 1 coil in both pickups. I have another set coming, but in the meantime I decided to try my hand and rewind the blown ones. I bought some enamel coated wire and made up a hand crank jig. I have stumbled onto a problem I need some help with. Ohm measurement. I know how to measure, but my reading just doesn't add up. Let me explain. OK now, I used 39 awg wire. I know that's a bit bigger than normal, most people use 42 gauge. My set that blew had a resistance of 17k on bridge. 8.5 each coil. Yes they were overwound. I removed all the wire and cleaned the bobbins and proceeded to rewind. Something was not right the whole way through winding. I was checking ohms during winding but the readings were way too low. I continued to wind a bobbin all the way out to it's edge until I couldn't get any more on it. I checked it there and I only have 924 ohms at that point. Everything stayed tight during the winding process, and pretty straight as well. I know the wire is slightly larger than originally used, but this just makes NO sense to me whatsoever. Can someone please give me an idea as to why this seems to have gone so wrong? Please help if you can. I didn't expect to get it up to 8.5k but this is bad. Yes I was reading on the 20k scale and it is an electronic multimeter. Thanks in advance.

[Mark Swanson]

Mike, hold everything here. first, what makes you think the pickups were "blown"? Pickups don't blow, and shorting one to ground will not hurt it at all. Your pickups were probably just fine and if your guitar didn't work then you most likely had a wiring error somewhere else. Too bad you didn't bother to ask before you tore your pickups apart and ruined a perfectly good set of pickups.
The wire you are rewinding with is the wrong stuff, you just won't get enough on the bobbins for this use. It sounds like you need to wind tighter, too but first you must get the right size wire, yes it makes that much difference.

[mike ryman]

Okay first. The reason for my thoughts of blown. I tested pickup leads with a mutimeter. No reading at all. So I took it apart. 1 coil showed continuity, the other none. So, 1 bad coil. 1 bad on neck as well as bridge. When I tore it apart, I found coil tap wires had touched ground. So I pulled them apart and tested each coil individually. Just the 2 wires coming from each coil. result, 1 had continuity, the other none. I have rewired several guitars and changed pickups in all 3 guitars I own. I'm quite used to working on electricals, but have never rewrapped coils for a guitar. I have however made coils for other uses. Never had this kind of problem. Hence my posting lol. I just checked the neck pickups coils again, 1 has 4.25k the other none. The possibility exists that I just may have got a bad set to begin with. I don't know. I took for granted that they were fine and didn't checked them when I bought them.

[Mark Swanson]

It is possible that your pickups were bad when you bought them, but depending upon who made your pickups and the reputation for quality they may or may not have, it is very rare for that to happen. If a coil doesn't read any resistance, then it is either broken in the wind or the connections to the start and finish are bad. It isn't "blown", that can't happen. If you looked at a coil-tap situation and a coil was grounded, then it is normal, because when a pickup is tapped for coil-cutting, the center connection between the two coils is brought to ground- that's how coil-cutting works. Having a connection touch the ground does nothing at all to hurt the pickup.

[mike ryman]

Okay. when i peeled wire coating off of coil harness i found that the wires for coil tap had touched against the shielding copper. That's why I figured blown. So I removed the shielded wire bundle down to just the 4 short wires coming out of the coil, I tested there. 1 showed continuity. Nothing on other one. Anyway, as I said I have another set that should be here today, so I will get some smaller wire and rewind them for another guitar project coming up. Thank you for your insight.

[Beate Ritzert]

Your example demonstrates how misleading Ohm values of pickups are.
What You are actually seeking for is inductivity. The inductivity is proportional to the number of windings. If Your wire is thicker, the specific resistivity of the wire decreases with the square of the diameter. So with thicker wire You actually expect lower Ohm readings if the number of windings remains the same.

Need an example?
I recently wound a pickup with very thick wire, diameter 0.2 mm, a bit less than 500 turns, filling the bobbin of a tele neck PU. Its DC resistance reads 37 Ohms (and the beast sounds nice...)

The resistance is, however, responsible for another effect: internal damping of the resonance of the pickup. The pickup with the thicker wire will sound differently, sharper, even if the inductivity has remained the same. You need to compensate for this.

[David King]

The original set had a resistance of 17k with both coils in series? In a HB pickup I guessing they used 43 AWG so dropping to 39 AWG would drastically lower your resistance as Beata explained. You'll have many fewer turns and the wire will have much lower resistance as well. Give them a chance, you might like the tone for some things.

[Brian Moum]

Mike - how much wire did you use? Quick check on a few sources shows resistance per 1000 feet of 39 awg wire as around 850 ohms. So logically, if your 924 ohm reading is correct, that should be about 1,090 feet.

By comparison, to get your original reading of 8.5 kOhm per coil using 42 awg takes something over 5,000 feet (nominally 1660 ohms per 1000)

[mike ryman]

Wow, info overload lol. First, Beate, thank you for that info. still kinda doesnt make sense but i understand most of it. Secondly, David, I may just keep the larger wire wind pickups. Definitely sounds interesting. On to Brian, as for how much wire? I have no idea. All I know is , I wound it as smooth and tight without breaking the wire as I could. I wound it out to the very edge of the bobbin. I did get some good news however, my second set of pickups arrived and I wired them in. I changed nothing about how it was done, and my guitar works perfectly. So at least I know it wasn't my original job of wiring that caused it to go bad. At any rate, I will probably end up keeping the larger wound coils and put them in a future project. I thank you all for your idea s and advice. Here is a picture of the body. I am quite happy with how it turned out.

[David Schwab]

Okay. when i peeled wire coating off of coil harness i found that the wires for coil tap had touched against the shielding copper. That's why I figured blown. So I removed the shielded wire bundle down to just the 4 short wires coming out of the coil, I tested there. 1 showed continuity. Nothing on other one. Anyway, as I said I have another set that should be here today, so I will get some smaller wire and rewind them for another guitar project coming up. Thank you for your insight.

You can't check pickups for continuity. You can test the resistance though. Sometimes pickups have a break in the coil, and they read open. That is often at the start or end points.

There is at least one pickup, the Duncan JB neck, that wont give a reading on a ohm meter because they use a capacitor to roll some low end off the pickup, and capacitors block DC. So the meter wont work with them.