Duncan JB

[David Schwab]

http://www.salvarsan.org/pickups/Coil_Estimator.html

Summary:
It estimates pickup windings counts from measured DC resistance.

It DOES NOT calculate resistance from winds.

Cool! I had your other widget bookmarked... the rectangular coil thingy.

You got real close with your guesstimate. After taping it was about 9.97K.

I came up with a formula that I use after I've wound a coil, and took a reading that lets me calculate either the winds needed for a certain DC resistance, or vice versa for that coil geometry and wire gauge.

I'll post it later... someone might find it useful.

[salvarsan]

Cool! I had your other widget bookmarked... the rectangular coil thingy.

You can save the current version and use it offline, y'know.

Since there are frequent small variations in vendor parts,
could you post the inside dimensions of your PAF bobbins?

Length, width, height are all I'm looking for.

BTW, these bobbin dementions may be hand-tweaked on the Coil Estimator page.

-drh

[David Schwab]

You can save the current version and use it offline, y'know.

D'Oh! Yep.. just did that.

Since there are frequent small variations in vendor parts,
could you post the inside dimensions of your PAF bobbins?

Length, width, height are all I'm looking for.

BTW, these bobbin dementions may be hand-tweaked on the Coil Estimator page.

They were Stew-Mac bobbins. The widget said I did a machine wound coil! I do have to say it was the nicest looking coil I ever wound. It was pretty dang tight too. I try to have minimal scatter these days.

It was fun to do a spur of the moment pickup with no expectations.

[salvarsan]

They were Stew-Mac bobbins.

(grumble)

Gotcha.

That's

• length = Stew,
• width = Mac,
• height = bobbins.

Thanks, Dave.

-drh

[David Schwab]

(grumble)

Gotcha.

That's

• length = Stew,
• width = Mac,
• height = bobbins.

Thanks, Dave.

-drh

I don't have any more to measure... but there was a discussion on the hight and thickness of the center core just recently.

I had measured the unwound bobbin then and got:

coil hight= .252", and .257" for the center post thickness on the screw and .259" on the slug.

I don't know what the length of the center core is... (and of course your coil wrap length increases as you wind on the wire already wound, right?)

Otherwise I'd suppose they are the same as any other humbucker bobbins. I read 2.649" for the length and 0.691 for the width of the bobbin measured from the top.

Does that help?

[salvarsan]

How big is that f*cking bobbin?!

I had measured the unwound bobbin then and got:

coil hight= .252", and .257" for the center post thickness on the screw and .259" on the slug.

Thanks, that's pay dirt.

I don't know what the length of the center core is... (and of course your coil wrap length increases as you wind on the wire already wound, right?)

That's accounted for in the computation and
is why there are 5 different winding models. They still need refinement.

Bucker bobbins have pole spacing to accomodate in 49.2, 50, and 53mm
string widths; add the width/dia. of one slug to get the outer core width.
This doesn't tell us how thick the core casting is, and it must certainly
vary with manufacturor.

If we guess that the plastic is .005" thick around the end slugs
(.1875" dia), the core length on a 50mm slug bobbin is
~55mm = 2.166" = ~2-5/32".

The same logic suggests that either I've erroneously put 53mm bobbin
measurements in the Coil_Estimator app, or that .005" core thickness at
the ends is too conservative a guess.

Otherwise I'd suppose they are the same as any other humbucker bobbins. I read 2.649" for the length and 0.691 for the width of the bobbin measured from the top.

Does that help?

Certainly, yes. You are the ONLY one who has ever replied to my
requests for bobbin dimensions.

With the grudging acknowledgment of others' indifference on the topic,
I, In the interests of science, have ordered bobbins (both screw and slug)
from StewMac and Mojo, for more empirical measurements.

News at 11.

-drh

[David Schwab]

You are the ONLY one who has ever replied to my
requests for bobbin dimensions.

That's funny.. I actually went and dragged that Stew-Mac kit out because someone asked, and someone else posted a dimension, then whle i had the kit in hand, I decided to take a break from soldering tiny connectors onto tiny wires and wind a pickup.

I would have measured the entire thing. I'd guess that the length of the core is similar to the thickness of the core in relationship to the pole holes... so you add that to the width of the pole spacing and there you go.

This was a standard width 'bucker... The guitar needs an F spaced pickup however.

The one addition I'd like to see to your widget is getting the resistance from the turns. Right now it's the opposite. (unless it's on there somewhere and I didn't see it)

[salvarsan]

The one addition I'd like to see to your widget is getting the resistance from the turns. Right now it's the opposite. (unless it's on there somewhere and I didn't see it)

I'm working on it.

The original idea was have a reverse-engineering tool
instead of a predictive tool, but it's obvious that you
need both as a validity check.

-drh

[David Schwab]

Ah! That makes sense... I hadn't thought about it that way.

I'm just sometimes curious what I'll get resistance wise with a certain number of turns. Both would be cool.

Nice coding, by the way.

[Stan H]

You can save the current version and use it offline, y'know.

Hate to sound like a real computer illiterate DA but, how do you do that?

[David Schwab]

Hate to sound like a real computer illiterate DA but, how do you do that?

I can only speak from doing it on a Mac... but I saved the page as a web archive file.

You should be able to save it as an HTML file too. I can also do "Save As Source" from Safari. I'd imagine you can do that with other browsers as well.

You can also view as source and copy and past it into a text file, and save that with the extension .html or .htm

[Stan H]

Thanks!

[soundmasterg]

David,

I finally found my Duncan JB specs...though I only tested it at 1KHz....and can't find the pickup at the moment.

Anyway, it's DCR is 16.41k, the ACR @ 1KHz is 23.04k, and the inductance at 1KHz is 8.021 henries. I did not measure the Q.

Hope that helps ya out.

Greg

[Joe Gwinn]

David,

I finally found my Duncan JB specs...though I only tested it at 1KHz....and can't find the pickup at the moment.

Anyway, it's DCR is 16.41k, the ACR @ 1KHz is 23.04k, and the inductance at 1KHz is 8.021 henries. I did not measure the Q.

The Q is completely determined by the AC resistance, frequency, and inductance.

At 1 KHz, 8.021 henrys have a reactance of 2*Pi*8.021*1000= 50,397 ohms.

For an inductor, the Q is reactance divided by AC resistance, or 50397/23040= 2.2.