Reverse wind/reverse polarity question...

[Neal]

Stupid newbie questions...
The wife and kids were out selling Girl Scout cookies yesterday, so I got a chance to work on my 'tinkering' list.
One of the things I got to tinker with was an old no-name guitar with a dead pickup. The winding was broken (the pickups have no tape wrapped around the coil, so it's easy to break a winding when changing strings or picking hard).
I'm considering rewinding it for the middle position as a reverse-wind/reverse polarity. I'm thinking about unwinding the coil onto a spool, then rewinding it back onto the bobbin. Then, I figured if I slipped the magnet polepieces out of the bobbin, and put them back in "upside down", I'd be reversing the polarity.
Here are my questions:
First, is it practical to re-use the existing wire, or will it be an exercise in futility?
Second, would this actually be hum-cancelling with the existing pickups, or would it be out of phase?
This old guitar intrigues me... it's got a crappy trem bridge which I've blocked, and is put together pretty cheaply. However, it's got a cool switching system:
3 single coil pickups (neck and middle each read 9.4 ohms!), and two 3-way blade switches...
Switch 1's 3 positions are: neck, middle bridge.
If switch 2 is in second position, switch 1 is : neck+middle, middle+bridge, neck+bridge.
If switch 2 is in the 3rd position, all pickups are muted (kill switch).
As an added bonus, a small slide switch controls a bass roll-off cap, which brings out the strat chime without being thin or harsh.
Any advice or tips would be appreciated!
Thanks!

[Dave Kerr]

I've never tried recycling wire, but from all accounts it's a royal PITA - absent real motivation to save it (it's a vintage pickup with PE wire that you feel you need to keep, for example) I'd grab a spool of wire off EBay.

RWRP means that the music signal will be in phase with the other pickups, and the hum will be out of phase. Take a magnetic compass to the pickups to determine whether the existing middle pickup is already RWRP, it may very well be already.

[Neal]

Thanks, Dave!
No, the middle pickup is not RW/RP... it hums in all positions. I think I've got a spool of wire here somewhere, but I'm not sure what gauge wire is on those old pickups. It's extremely tiny.... possibly 43 gauge.
Thanks for the advice!

[David King]

You could take the original middle pickup out and remagnetize to flip the polarity then switch the leads. 2 good sized neodymium bar magnets glued to the jaws of a vise will do this for you.

I guess if you have to rewind the pickup anyway then it's reasonable to flip the magnets manually but you might find the good end of the busted wire, resolder it to the eyelet and be good to go.

[Possum]

...

If you want it humbucker you have to wind it backwards, so looking from the top the wire would go clockwise around the magnets, that is if the the others are traditional with anticlockwise wind looking down from the top. No, you don't want to try to save the wire unless you have a spare 15 hours on your hands and don't mind splicing back together all the places you'll break the wire :-) And you have to have the magnets opposite polarity of the others. There is a cool trick to check any pickup's polarity electrically. Go to an auto supply place or any hardware store and buy the cheapest piece of junk multimeter they sell with a NEEDLE readout. Hook it to your pickup with black lead to ground and red to hot then switch it to ohms. Take a fat piece of iron and push it down towards the pole pieces in a quick motion. The needle will jerk left or right. Then test the other pickups in the guitar you're putting it in, if they all jerk the needle in the same direction then they are all in phase with eachother and you won't get any accidental out of phase tinny tones.....

[Mike Sulzer]

If you want it humbucker you have to wind it backwards,

A humbucker (that is, a pickup that cancels hum from magnetic fields) needs one of the two coils to have reverse magnetic and electrical polarity. The first is achieved by reversing the direction of the magnetic field. The second can be achieved by interchanging the two coil wires. It is not necessary to rewind the pickup.

[Possum]

....

No its not necessery but if you get a coil short to the poles and the strings touch the poles, guitar turns off. Its fine for hobby work but not for products for sale.

[David King]

Possum,
In basses, a coil simply may not short to the magnets. There are too many active eq circuits that rely on a floating ground. Magnets need to be grounded for noise reasons but if the coil shorts to the magnet you've just shorted out 1/2 the preamp. This is a disaster and is the reason I got into making pickups in the first place. (If you want it done right you need to do it yourself.). If you take your hot from the start you know right away whether you have a short. I'm pretty confidant that the polymide tape I use to insulate the magnets won't be breaking down anytime soon

[Neal]

I appreciate all the responses, guys. For the short term, I've put in a pickup from the 'stray pickup' box. It has a lower output than the other two in the guitar, but it'll work until I get the original rewound.
I'm almost hesitant to rewind it, because I'm afraid I'll enjoy it too much... I already have too many projects on the back burner, and if I add another time consuming hobby, I'll never get anything done!
I've been slowly grooming my 8-year-old daughter to be my partner in crime (read: keeping me company while I tinker in the music room), so maybe she'll be my pickup maker when she shows a little more patience.
Thanks, Gents!

[Possum]

....

I don't think we were discussing active bass pickups here, but strat pickups. Many vintage strat pickups have shorted winds to the magnets, in fact this can help fatten up the tone sometimes, but personally I insulate my magnets on all my single coil stuff as regular practice. Grounding magnets adds metal to the circuit so you are adding inductance which changes the tone, I suppose in active bass pickups you guys are stuck with doing that. I don't make bass pickups in my product line because I don't play bass and don't know enough about what bass players want, I do however make pickups for drummers

[Mike Sulzer]

Grounding magnets adds metal to the circuit so you are adding inductance which changes the tone,

I do not see how the electric potential of the magnets affects the inductance. It should change the capacitance a little bit. You do want to be a bit careful how you do the grounding. For example, if you were to wrap a piece of foil around the magnets, that is, a shorted turn right around them all, that could affect the sound.

[Possum]

...

It doesn't make a huge inductance change but there is a definite measurable effect most noticeable in the AC resistance. This is actually one way to spot a short to the poles. Alnico after all is mostly iron and is metal, replace it with ceramic and the inductance drops way back.

[David King]

It seems to me that I've read here that Alnico has very little inductance.

[Possum]

....

No thats completely wrong. Stick an alnico mag in a bucker and use your Extech, then replace it with a ceramic, very big difference....

[David Schwab]

Right, alnico has more metal than ceramic... but you ground the magnets in a humbucker, right?

Here's an easy test. Ground the magnets in a Strat pickup using some copper tape on the bottom. If needed you can use some conductive paint first. Run that wire separately from the pickup leads. Now wire it to a switch, and then to ground.

Do you hear a difference when the magnets are grounded? My tests say you wont, at least nothing worth worrying about. I hear no difference at all.