# Thread: What Could Account For This?

1. ## What Could Account For This?

Two humbucker coils. One wound with 5720 turns and the other wound with 5600 turns. Same speed, tpl and tension. But the coil with less turns has a higher resistance and the one with more turns has a lower resistance, 4.40 and 4.23 respectively.

Explanations?

2. Originally Posted by jrdamien
Same speed, tpl and tension.
Same wire? Measured at the same temperature?

3. Originally Posted by Leo_Gnardo
Same wire? Measured at the same temperature?
Yes and yes, within a few degrees (or however much a room might change from body temp). Or how great of a temp change is required to account for this? The coil that has less turns but a higher resistance was wound second, so after the room would have warmed some.

All that is left is mechanical aberration, correct? Or am I not thinking of something?

4. Internal shorts would be the most likely answer followed by stretching.
Temperature is very relevant here too -you can watch the resistance change just while you hold the coil in a warm hand.

5. Originally Posted by jrdamien
Two humbucker coils. One wound with 5720 turns and the other wound with 5600 turns. Same speed, tpl and tension. But the coil with less turns has a higher resistance and the one with more turns has a lower resistance, 4.40 and 4.23 respectively.

Explanations?
Confusing which had more turns would explain it to an error of about 1%. Measure the inductance to confirm the theory.

6. Originally Posted by David King
Temperature is very relevant here too -you can watch the resistance change just while you hold the coil in a warm hand.
Copper coefficient near room temp is approx. 0.4% per degree Celsius. The resistive difference between room temp and held in hand for awhile, say 10 degrees C, can easily be 4%. This used to flummox me something awful, thought I'd wrecked pickups by wax dipping, until I looked it up. Let 'em sit at room temp for a good long while then measure.

7. Originally Posted by nickb
Confusing which had more turns would explain it to an error of about 1%. Measure the inductance to confirm the theory.
I'm definitely not confusing which has more or less turns.

EDIT: Low meter battery. There is no difference in inductance. Both are at 2.16.

8. Originally Posted by Leo_Gnardo
Copper coefficient near room temp is approx. 0.4% per degree Celsius. The resistive difference between room temp and held in hand for awhile, say 10 degrees C, can easily be 4%. This used to flummox me something awful, thought I'd wrecked pickups by wax dipping, until I looked it up. Let 'em sit at room temp for a good long while then measure.
Sure, and after having been left alone the coils are now 4.3 & 4.16. And this is what I expect of any coil I wind. But it doesn't seem to account for the difference, though.

9. Originally Posted by David King
Internal shorts would be the most likely answer followed by stretching.
I think David hit the nail on the head...Stretching is more likely especially if hand guided/wound. A short is also possible (machine or hand guided).

It could also be smaller wire OD on the one with higher DC resistance...this can happen even on the same spool. Mic the OD of the two coils at both start & finish to see if wire OD could be the culprit.

Are you machine winding with auto-traverse or hand guiding your wire?

If hand guided, TPLs could be slightly off causing your situation. This would be hard to tell because your off-set is so little. Generally a lower TPL will generate a bigger coil with higher DC resistance even with the same turn count.

10. Originally Posted by Jim Darr
I think David hit the nail on the head...Stretching is more likely especially if hand guided/wound. A short is also possible (machine or hand guided).

It could also be smaller wire OD on the one with higher DC resistance...this can happen even on the same spool. Mic the OD if the two coils at both start & finish to see if wire OD could be the culprit.

Are you machine winding with auto-traverse or hand guiding your wire?

If hand guided, TPLs could be slightly off causing your situation. This would be hard to tell because your off-set is so little. Generally a lower TPL will generate a bigger coil with higher DC resistance even with the same turn count.
Machine wound, auto traverse, identical tension. Same spool of wire, coils wound back to back.

Maybe it was just an aberration but it's big enough that it's bugging me.

If hand winding TPL could account for this, but it would have to be a rather estranged tpl.

11. What kind of circuit is the turns counter? Some mechanical ones(reed switches, lever switch) screw up or bounce.

12. Originally Posted by mozz
What kind of circuit is the turns counter? Some mechanical ones(reed switches, lever switch) screw up or bounce.
mozz, Very good point!! Didn't think of that.

jrdamien, What type of winder are you using?

13. Originally Posted by Jim Darr
mozz, Very good point!! Didn't think of that.

jrdamien, What type of winder are you using?
It's a homebrew winder with a mechanical traverse. The counter is digital triggered by an optical sensor.

If anything it's a tension issue or wavering somewhere in the traverse mechanism.

However, after posting this earlier, I've since wound a dozen sets of coils. Everything seems fine...fingers crossed.

It's still bothersome, though.

14. All posts have good insights and considerations. Temp, humidity...2 big variables. Small changes make a difference. I've had - and I think we've all had - similar experiences at points in our career and probably still do from time to time: this is good stuff, really. When in doubt, start again. Customers deserve our absolute best, period!

15. Originally Posted by JGravelin
All posts have good insights and considerations. Temp, humidity...2 big variables. Small changes make a difference. I've had - and I think we've all had - similar experiences at points in our career and probably still do from time to time: this is good stuff, really. When in doubt, start again. Customers deserve our absolute best, period!
That is absolutely the bottom line. So, even if 'this' is just me being bothered by an inexplicable deviation and wondering all the things I might not know as to why, it's all in the end of always making great pickups.

And yes, lots of good stuff and online to always have and for others to learn from.

16. Originally Posted by jrdamien
I'm definitely not confusing which has more or less turns.

EDIT: Low meter battery. There is no difference in inductance. Both are at 2.16.
If the inductance is the same ( which is very surprising) then at least you know you don't have a shorted turn.

17. Originally Posted by jrdamien
Two humbucker coils. One wound with 5720 turns and the other wound with 5600 turns. Same speed, tpl and tension. But the coil with less turns has a higher resistance and the one with more turns has a lower resistance, 4.40 and 4.23 respectively.

Explanations?
Are both coils 49.2mm, 50mm, 52mm or a mix?

18. If it's possible that the counter may be counting wrong ,a small jeweler scale can easily weight the different weight of the coils .

19. Originally Posted by nickb
If the inductance is the same ( which is very surprising) then at least you know you don't have a shorted turn.
But why would that be surprising?

20. Originally Posted by jrdamien
But why would that be surprising?
If everything else is the same i.e.the number of turns is the only difference, then the inductance is proportional to the number of turns squared. The resistance is proportional to the number of turns. Thus the inductance should be a more sensitive measurement.

5720/5600 = 2% difference in resistance
(5720/5600)^2 = 4% difference in inductance

21. Originally Posted by nickb
If everything else is the same i.e.the number of turns is the only difference, then the inductance is proportional to the number of turns squared. The resistance is proportional to the number of turns. Thus the inductance should be a more sensitive measurement.

5720/5600 = 2% difference in resistance
(5720/5600)^2 = 4% difference in inductance
I misspoke when I said they were the "same." I meant they were not wildly different or different enough to account/explain for the dc I was seeing.

If I have an inductance of, say, 1.5 (or whatever) in the larger coil the difference between the two would be .06 or so. So if I have my meter on a less sensitive selection it probably wouldn't show a big difference or any difference.

22. .

If the inductance is equal then the number of loops should be the same. That leaves the resistance difference to wire manufacture variations. Many variables that could cause the wire to be slightly thicker/thinner along its whole length at the tiny diameter of pickup wires, mechanical and chemistry both.

I remember something about steel sheet rolling will have thinner ends and thicker center because it starts out as a thick block and gets squeezed out and stretched. There was even a term for it but it escapes me at the moment. Point is the spool you have could have been thick or thin size at the beginning and changed along the five miles of wire spread across those pickups. Wouldn't take much that wire manufacturing thickness gages could barely discern but have enough of it and the resistance changes.

Might plot out which pickup was done first, readings vs length and any you wind in sequence after. Maybe see a rising/falling trend in the order built.

.

23. Knowing exactly how wire is made would be instructive here. Anyone care to expound on the finer points of drawing copper through dies?

24. .

The first video below doesn't dwell on the wire resizing operation, but the second one does. See the surging of the continuous sizing machine farther in the second video. Those stages with rows of opposing offset wheels are there to straighten the wire. All of the resizing, the gripping, and the straightening operations work harden the material which will alter how it stretches in later operations. Tension on the wire-making take-up spools could even change the wire as wound from the spool inner diameter to the outer large diameter as the circumference of the spool changes the take-up speed. Annealing furnace variations can alter the draw process. The third video gets closer to pickup wire manufacture. Everything that is touching that wire the whole way through can be a variable on the output.

This is all not including the wire chemistry to start with. New from the ground copper vs reclaimed copper. Some copper mines have higher contents of other alloying materials already in the copper at some acceptable level of 'contamination', but it's all a variation.

At least remember that guitar potentiometers have a 20% tolerance band of acceptable factory variation and better tone caps have 5% tolerance. I have seen a 5% DCR reading across a three pickup Strat set.
OP's two bobbins, assuming aiming for the same number of winds, are 2% off each other and the resistance variation is 4%, while a low sample, is a lower tolerance than the circuits that gate the pickup tone into the amp.

I have often been curious what the output variation is of bigger pickup manufacturers like Fender/Gibson/Duncan/etc daily and over weeks, partly due to my interest in guitars but also on the day job side I'm involved with manufacturing (automotive). What wacky shenanigans go on in their plants?

25. If you combine some of the answers?
Are the bobbins the same (height, width, flange)?
Do both coils weigh the same?
Mic the outside diameter of the 2 coils, are they the same diameter?
If you answer no to any of the above, then the two bobbins are not wound the same and will read differently!
T

26. Just one of the MYSTERIES OF WINDING PICKUPS

27. Amen.

Pickups are as variable as people, and you will never wind two coils exactly alike. And even if you managed to do it... they would probably sound completely different from each other. The trick is not to obsess over the numbers, but to obsess over the sound

Ken

28. Originally Posted by ken
Amen.

Pickups are as variable as people, and you will never wind two coils exactly alike. And even if you managed to do it... they would probably sound completely different from each other. The trick is not to obsess over the numbers, but to obsess over the sound

Ken
Absolutely. But, in a production scenario in which I am winding familiar coils and 'this' happens, it makes me wonder and ask.

Obviously every pickup made isn't being put in a guitar first and played. The best 'I' have to go with are subject limits of anomaly that tell me a given coil or pickup shouldn't be sent out.

29. Originally Posted by jrdamien
Absolutely. But, in a production scenario in which I am winding familiar coils and 'this' happens, it makes me wonder and ask.

Obviously every pickup made isn't being put in a guitar first and played. The best 'I' have to go with are subject limits of anomaly that tell me a given coil or pickup shouldn't be sent out.
I agree that it's best to strive to understand tolerances, and not write it all off as luck of the draw. I think you have to wind a few more coils to those same specs and see how they deviate. The sample size is just too small to draw a conclusion. It might be that your winding process stretches the wire, and that by reducing the diameter over some length you get a difference DC resistance in the end.

30. Pickups are made of of a collection of parts made by humans, all with different tolerance levels for the parts they themselves make. In other words, somebody who is tired on Friday afternoon after lasering bobbin flats all day and wants to go home is not going to be as fussy about the parts they made as I would be, because I'm OCD about pickups and make my own parts. Each part you add to your pickup adds its own set of variables to the finished piece, and sometimes the accrued tolerances can really mess you up.

I have found the best way to deal with the problem is to test *each step* in your process after you do it.
Assembled your bobbin? Measure it with calipers and make sure the magnets are correct and tight before you wind the coil. Wound your coil? Make sure your coil is complete and not shorted or open before you pot the pickup or wrap it in tape. Wrapped or potted the coil? Check it again. Did the measurements you get this time change from the ones you took after winding? Why?

This will teach you how each step in your process can change your finished product, and can help you find what exactly went wrong. Besides, the info you will generate will give you an education in pickup making you won't get on YouTube.

Yes... I test every pickup I make in a guitar before I send it out as part of final inspection. How are you going to know if you have a defective product if you don't test it?

Ken

31. I think electrical tests would be sufficient to pick up problems in production of the same pickup model.

Originally Posted by ken
Pickups are made of of a collection of parts made by humans, all with different tolerance levels for the parts they themselves make. In other words, somebody who is tired on Friday afternoon after lasering bobbin flats all day and wants to go home is not going to be as fussy about the parts they made as I would be, because I'm OCD about pickups and make my own parts. Each part you add to your pickup adds its own set of variables to the finished piece, and sometimes the accrued tolerances can really mess you up.

I have found the best way to deal with the problem is to test *each step* in your process after you do it.
Assembled your bobbin? Measure it with calipers and make sure the magnets are correct and tight before you wind the coil. Wound your coil? Make sure your coil is complete and not shorted or open before you pot the pickup or wrap it in tape. Wrapped or potted the coil? Check it again. Did the measurements you get this time change from the ones you took after winding? Why?

This will teach you how each step in your process can change your finished product, and can help you find what exactly went wrong. Besides, the info you will generate will give you an education in pickup making you won't get on YouTube.

Yes... I test every pickup I make in a guitar before I send it out as part of final inspection. How are you going to know if you have a defective product if you don't test it?

Ken

32. Originally Posted by John Kolbeck
it's best to strive to understand tolerances ....
you have to wind a few more coils.....
The sample size is just too small.....
Same here.
Canīt believe we have reached more than 30 answers wondering about unimportant differences (IF there is any audible one, that is) between 2 handwound pickups, on a homemade machine, within 10% (or less) from each other, and based on a grand total sample of 2 (two).

33. I think electrical tests would be sufficient to pick up problems in production of the same pickup model.
I have a 5S7 (1957 Strat style) pickup in my collection I made years ago. It looks perfect, it electrically tests perfectly, but for some weird reason it has a strange fizzy distortion product when played loud I can see on my scope. Play it soft, it's fine. Problem is I can't figure out why it did it, and it was the only one I ever made that did that. I keep it as a reminder to test everything before it leaves here whether it needs it or not.

The only explanation I can think of is some kind of insulation issue on the coil wire. Like I said, it's electrically perfect.

34. You're right about that. I had no idea the sample size was so small. Leo would have been happy with those measurements, as his pickups were +- 20%.

Ken

35. Originally Posted by jrdamien
Absolutely. But, in a production scenario in which I am winding familiar coils and 'this' happens, it makes me wonder and ask.

Obviously every pickup made isn't being put in a guitar first and played. The best 'I' have to go with are subject limits of anomaly that tell me a given coil or pickup shouldn't be sent out.
It might sound perfectly normal. But in a production scenario, just rewind the coil is it's out of spec. That's what I do. Why take chances.

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