Guitar Pickups Coil Ringing Test Electric Testing PUP

"Wild_Bill"

** The pickup has a steel ( possibly Alnico ) magnet and soft iron pole pieces, this makes for a lossy inductor - bit like a normal loudspeaker voice coil is.

If you remove all of that, the inductance goes down and you have a low Q inductor because of the high resistance.

... Phil

I attempted to explain that I've disassembled the humbucker pickup, separated the 2 coils, and have removed all the metal influences from the coils. The magnet, pole pieces, screws, frame plate and cover have been removed and set aside.

Just a plastic bobbin and hundreds of turns of wire.. there is no metal, other than the coil of wire. The desk where I'm checking the coils is wood.

At that point, there weren't even any long signal leads attached to the coil.

So I've reassembled the pickup as originally wired, with a short pigtail of shielded pickup coil cable.

I added an inline 1/4" jack to the pigtail, and plugged my VOX AM30 Amplug headphone amplifier into the pigtail, and held the pickup near the guitar strings (in the open space between the guitar's neck and bridge pickups..

and Buhh-Zinga! plenty of output from this Epiphone humbucker pickup.

This isn't a definitive performance test, but the notes sound very clear and strong for all the strings. I immediately plugged the H-P amp into the guitar, and the Epiphone pickup sounded essentially the same as the guitar's DiMarzio DP155 bridge pickup.

I hadn't suspected that the Epiphone pickup was bad, but I wasn't sure since it hadn't been installed in a guitar since I've had it.

BTW, I didn't place the metal cover back on the pickup, and I'm aware that a metal cover will create a fairly large area for eddy current to pass, and slightly affect the peak frequency.

I think I'll make a little gantry for suspending test pickups over the guitar strings, for a quick bench check.

But I still don't know why the Bare coils didn't ring higher than 4 rings. It's possible that shorted turns could exist even though the output seems to be OK.

Oh, and forgot to mench.. the inductance measurement for the combined coils in this pickup (when it's fully assembled) reads about 5.5 H.

-- Cheers, WB .............

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Because the inductance of the coil alone is VERY much smaller than the inductance when it is placed inside the pole pieces, while the resistance of the coil does not change. Thus the Q changes drastically because the ratio of inductance to resistance changes radically.

So, I've disassembled another Epiphone humbucker pickup of the same basic type/series (but instead the neck pickup), and the Ringer Test results are the same (4 rings whether assembled or disassembled).

Assembled pickup DC resistance 10.8k ohm, inductance 4.7H.

Disassembled pickup, coils separated from magnet, frame plate.. individual coils inductance 2.3H

Bare coils, no screws or core plugs.. 830mH each.

-- Cheers, WB .............

"Wild_Bill"

** The number is visible cycles of ringing is a guide to the Q of a resonant circuit - the Q is approximately equal to the number of cycles.

So, your pickup coil has about a Q of 4 - either bare or assembled.

Why?

The frequency of ringing is much higher when bare.

Q = the ratio of impedance to resistance at a given frequency.

.... Phil

I'm guessing that you're unfamiliar with the Sencore Z-Meters Ringer Tests. They're capable of indicating shorted single turns. Fault-free inductors normally ring 10 rings or higher.

Placing a single turn of wire (with ends touching forming a conductive turn) around an inductor will generally yield a Fail/1-thru-9 test result.

These testers work reliably for any type of inductor/transformer commonly used in electronic equipment circuits (no core material or ferrite-type cores, not steel core types as mentioned previously).

Guitar pickup assemblies aren't typical circuit inductors, however I kinda expected them to Ring Test normally with the steel screws and cores removed.

-- Cheers, WB .............

"Wild_Bill"

** Demonstrating that the Q is 10 or more.

As any DELIBERATE inductor will.

** Errr - cos that reduces the Q. ** Yep - ferrite cored and air cored deliberate inductors have high Q factors. ** Show how easy it is to be wrong when making silly guesses.

.... Phil

Your fabricated Deliberate Inductor term sounds very similar to the term Chemical Fuse.

You might be surprised/shocked to discover that many folks understand inductors.

Use all the space you need to show how many small components exhibit over 5H of inductance, which aren't inductors.

Would those components be Accidental or Coincidental inductors?

The Sencore Ringing Test isn't a specific measurement, it's an indication.

The inductance of an electric guitar pickup is the pickup's most significant characteristic.

-- Cheers, WB .............

For those who believe that the output of a guitar pickup is primarily related to the coils' DC resistance readings, I suggest some reading would be worthwhile.

Not from sources where the "experts" claim that the output of this model of pickup is 13.8, when they don't even understand what the 13.8 on their ohm meter represents. These are often the same folks that routinely refer to the cable connector on the guitar as the Input Jack.

The only importance of the 13.8 reading is that's the only thing their $5 DMM from Harbor Freight tells them. Immediately they understand that a 13.8 is almost twice as hot as a 7, while their misguided deduction realistically doesn't mean squat.

-- Cheers, WB .............