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Checking Pickup Resistance While In Guitar?

Bruce R

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I am interested in checking the resistance of the pickups in my guitars, without opening it up. I am wondering how accurate it is when simply plugging in a cable and measuring it that way?
 
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Strings Jr.

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I am interested in checking the resistance of the pickups in my guitar, without opening it up. I am wondering how accurate it is when simply plugging in a cable and measuring it that way?
For passive pickups it can be very accurate. Close enough to see what you got without opening it up. Just be sure to turn your controls up to 10 before checking.
 

Bruce R

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Cool, thanks! My tech did it on one of my guitars and it seemed to work fine. I was just wondering if there was some 'play" involved as I am thinking of swapping out a couple pickups and wanted to compare the ones in my guitar with those still in a box.
 

Strings Jr.

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Cool, thanks! My tech did it on one of my guitars and it seemed to work fine. I was just wondering if there was some 'play" involved as I am thinking of swapping out a couple pickups and wanted to compare the ones in my guitar with those still in a box.
Measuring through a cable will get you in the ballpark with little effort. If it's important enough to be more precise, then it's important enough to open it up and check the pickup directly.
 

Bruce R

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Will removing the controls plate in the rear and directly measuring at the volume pot be the same?
 

Strings Jr.

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Will removing the controls plate in the rear and directly measuring at the volume pot be the same?
If you're referring to a Les Paul, yes, you can do that without un-soldering the pickup lead.
Again, be sure the controls are on 10 and the toggle is not in the middle position.
 

Bruce R

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Oh, yes... a 2014 R0. I did a little experiment this time; I used a 6' cable, a 6" (patch) cable, and then I measured at the volume pot(s). They were all within a cent or two, with the highest reading at the pot. With Custombuckers, the bridge pu, with a 6' cable it measured 7.95k, with the 6" cable it was 7.97k, and at the pot 7.98k. Just for giggles I went right back to the 6" patch and it showed 7.98k! The neck pu measured from 7.92k - 7.94k.

The reason I was measuring was that the neck pu is a bit louder and boomier, so I need to really drop it to get the two pickups somewhat the same, volume-wise. I measured the pickups a couple of weeks ago at a friend's house and found the neck pu was a shade "hotter" (at 7.84k, against the bridge at 7.62k)) so I was thinking of adding a different bridge pickup. I measured again over the weekend and then again today and it shows the bridge pu is a few cents hotter. I confirmed this measuring both pickups all 3 different ways.

Thanks for your help!!
 

PaulD

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The length of the cable is irrelevant, even a long cable will have a resistance of less than 1 ohm (when measuring an 8K pickup that amounts to less than 0.0001% error!). The issue when measuring pickups in circuit is that you are measuring the resistance in parallel with the volume pot resistance, an 8K pickup in parallel with a 500K pot will give a reading of 7.87K. The reading in circuit will always be slightly less than the reading would be out of circuit, measuring at the pot makes no difference it is still in circuit.
 

Bruce R

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Thank you, gentlemen, I really appreciate it. That is very useful information.
 

El Gringo

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For passive pickups it can be very accurate. Close enough to see what you got without opening it up. Just be sure to turn your controls up to 10 before checking.
How do you do it ? Where do you put the thingies from the multimeter ?
 

Strings Jr.

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How do you do it ? Where do you put the thingies from the multimeter ?
Plug your cable in to the guitar as normal.. With your controls on 10, select one pickup with your toggle. Touch one of your meter leads to the tip on the other end of the cable, and the other lead to the sleeve portion. To check the other pickup, simply flip the toggle to the other pickup and do the same thing.
 

El Gringo

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Plug your cable in to the guitar as normal.. With your controls on 10, select one pickup with your toggle. Touch one of your meter leads to the tip on the other end of the cable, and the other lead to the sleeve portion. To check the other pickup, simply flip the toggle to the other pickup and do the same thing.
Thank You kindly Strings Jr. I really appreciate your help and immense knowledge !
 

Strings Jr.

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The length of the cable is irrelevant, even a long cable will have a resistance of less than 1 ohm (when measuring an 8K pickup that amounts to less than 0.0001% error!). The issue when measuring pickups in circuit is that you are measuring the resistance in parallel with the volume pot resistance, an 8K pickup in parallel with a 500K pot will give a reading of 7.87K. The reading in circuit will always be slightly less than the reading would be out of circuit, measuring at the pot makes no difference it is still in circuit.
I believe that is in the ballpark.
 

PaulD

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Not so much in the ballpark but exactly right, If you know the exact resistance of the pickup winding and the pot then you can calculate what the parallel resistance is using the formula 1/Rtotal = 1/R1 + 1/R2, a pickup that measures exactly 8K in parallel with a pot that measures exactly 500K will give a reading of exactly 7.87K.

Of course in order to know the exact resistances of the pickup and pot you would have to de-solder them and measure them out of circuit and having done that you wouldn't need to do do the calculation - somewhat of a catch 22! :)
 
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