Can a pickup's ohms be measured while it's still in the guitar?

[chamberpop]

Thanks for any responses or advice.

c-pop

[cband7]

At the least you'd have to get access to the back of the selector switch. Deselect that pickup, measure from the hot connection on the switch to ground (hopefully). Check the schematic for your particular guitar.

.

[chamberpop]

Thanks cband!

They are both Teles, an American Standard and a '56.

So just pop the control plate and de-select the pickup I want to measure?

I assume place the red wand on the yellow wire solder joint where it connects to the switch? And the black wand to the white? Or not?

Thanks again for the advice.

[winny pooh]

I get readings just fine with the controls full up and touching the ground and hot of a guitar cable plugged into the guitar...

[Ronsonic]

You can get close enough measuring at the output jack, with the volumes full up and only one pickup at a time selected.

If you really want to get more precise you can calculate the effect of having the volume control in parallel, but no need to bother. DCR is only a crude measure of what a pickup does anyway so measuring a hundred or so ohms low is no big deal.

[vanguard]

Originally Posted by Ronsonic

You can get close enough measuring at the output jack, with the volumes full up and only one pickup at a time selected.

If you really want to get more precise you can calculate the effect of having the volume control in parallel, but no need to bother. DCR is only a crude measure of what a pickup does anyway so measuring a hundred or so ohms low is no big deal.

this. just measure the end of a cable plugged into the guitar.

[copperheadroad]

A pickup will usually read a little lower installed in a guitar

[jefrs]

Originally Posted by vanguard

this. just measure the end of a cable plugged into the guitar.

remember to turn all knobses to maximum.

The pots are at least 250k, so you will get a reasonably accurate resistance of the pickup 'cos it's a lot less.

[frakenstrat]

i made myself a special cable where i lopped off the probe ends and soldered on a 1/4" jack. plug it into the guitar and you can read what the pickups measure through the circuit. granted, it won't tell you what the pickups will really sound like, but at least you won't get off readings if you don't have to factor in your capacitance.

[cband7]

Originally Posted by winny pooh

I get readings just fine with the controls full up and touching the ground and hot of a guitar cable plugged into the guitar...

Classic case of I can't see the forest for the trees: I'm too much the technician - I always think of disassembling first.....

[Rob DiStefano]

truthfully, what does single coil pup resistance matter/mean? not much.

what does matter more is how the pup sounds. pup resistance is a direct relationship to the amount of copper wound around the bobbin, and the diameter of said copper wire.

it's not the direct resistance that matters, it's the pup's materials, build, coil turns and tension that will dictate its tone/volume. the build means both the pup's design and assembly process. if the materials are 'proper' (fiberboard flatwork and not plastic bobbins, alnico V or II or III mags, formvar or enameled 42awg), the rest is up to the shape of the coil (tall strat, lower and wider tele bridge, squat p90, etc), the number of turns around the bobbin and the tension applied during winding. imo, the winding factor isn't all that important (linear, scatter, whatever), but others feel differently. and lastly, the number of wire turns will definitely shape the tone and volume for a given bobbin shape - typically, less turns for more treble bite and clarity, more turns for increased mid-range and warmth.

so, if the materials and build are standardized (this is important - plastic and fiber bobbins are not equal in this matter), then it's coil turns that count (pun intended), and when there are more turns of copper, the resistance goes up. without a winding machine counter, one could spot check the coil resistance to determine at various stages of the wind what the pup will offer for tone and volume. with a tele bridge pup and the aforementioned pup material/build parameters, 10000 turns will roughly deliver 8k resistance. typically it takes a good 1000 turns to perceive tone/volume differences.

[teleman55]

Originally Posted by winny pooh

I get readings just fine with the controls full up and touching the ground and hot of a guitar cable plugged into the guitar...

+1.

[Enaitz]

I'm starting to think also that pickups DC resistance means nothing.

The other day I measured all the pickups I got around and I obtained this:

Seymour Duncan Little 59 (neck): 9'46
Lace Sensor Silver: 7'42
Dimarzio Chopper: 9'01

Rumpelstiltskin White Rope Tele neck: 6'65
Rumpelstiltskin White Rope Tele bridge: 6'67

Squier Strat Middle: 5'66

Epiphone Les Paul Standard neck - 57CH(G): 8'35
Epiphone Les Paul Standard bridge - HOTCH(G): 14'19

Burstbucker 1: 8'32 (Waxed)
Burstbucker 2: 8'44 (Not waxed)

Tonerider Alnico IV Classic neck: 7'63
Tonerider Alnico IV Classic bridge: 8'49

Whatever it means...

[Rob DiStefano]

it's not that coil resistance means nothing, it's just that it has less or no meaning when comparing pickups for tone and output.

think of pup resistance as an indicator of sorts - but knowing the pup materials and build is very important!

if two pups are the precise same materials and build, but the coil turns are different, the resistance will be an indicator of which pup will/might have more coil turns, and more coil turns might mean a perceived 'warmer' tone and increased output. when i say 'coil turn difference', it typically takes a goodly 1000 turns to make that perceived tone/volume difference ... maybe. a vast difference in resistance - say, 6.7k ohms (about 8500 turns) versus 8.3k ohms (about 10500 turns) for a tele bridge pup - will almost always show the pup with the lower value to be more treble based (maybe to the point of being shrill), while the higher value pup will be more mid-range tone based and sport more usable volume.

[Rhomco Guitars]

The only time I care what the reading is, is when I am writing a "For Sale" description and when I have two identical pickups and need to know which one is the neck vs. the bridge.
Rob

[Derek Kiernan]

RTotal=1/([1/R1]+[1/R2])
or
(measured Ω at meter) = 1/([1/pickup Ω]+[1/volume pot Ω])

What you want to do is change this so we're subtracting the volume pot's resistance from the measured total:
R1=1/([1/RTotal]-[1/R2])
or
(pickup Ω) = 1/([1/measured Ω]-[1/volume pot Ω])

You could also think of it as (for quick calculation):
(pickup Ω) = [(volume pot Ω)x(measured Ω)]/[(volume pot Ω)-(measured Ω)]


example:
250kΩ volume pot
unknown pickup resistance
5.86kΩ measured resistance


If you do a simple plug and chug, you get 6.00kΩ for the pickup. The tone pot acts as an impedance control and does not factor in the calculation. Cable resistance will be negligible, deviation of the volume pot from its rating won't matter much... try plugging in 200k instead of 250k and see how that affects your results. The temperature changes from a pickup sitting in your hand would vary readings more.

[Becky Lawrence]

Hey Derek and glad to see that you're taking notes the other night when Bill spoke with you about an hour on this topic! Bill says that he's preparing to include some of this very information in his website section Pickupology but in a different way - more simplified which can help players learn more about pickups and their guitars. Btw, Bill had explained this same information to our friend Bruce which I hope he'll come in to write here too! Love, Becky