How to check pickup resistance and polarity?

[roadsleeper]

Hi all,

I have two SD Alnico II Pros that have been in and out of my Strat so many times I can't remember if I put the one that was supposed to be the mid or the neck in their correct positions...

As I understand it, I can use a voltometer to check the D.C. resistance of the pickup and thereby see which one goes in which position. Is this right? SD's specs call for the Alnico II Pro to read at 6.4k... how do I know which will go where?

Also, I'm almost certain I didn't buy one as a RW/RP for the mid, but how do I check this?

Any help would be tremendous!

 

[BlueGuitar]

Re: How to check pickup resistance and polarity?

If the two Alnico II Pro pickups you have stick together magnetically if placed together top-to-top, it is safe to assume that one of them is the RWRP middle pickup. Now figuring which of the two is supposed to be the middle pickup is another issue. If the bridge pickup is also single coil, then the middle pickup should stick to the top of that pickup as well. But if you have a humbucker in the bridge you would have to do other tests...

 

[roadsleeper]

Re: How to check pickup resistance and polarity?

you would have to do other tests...

What would those tests be?

 

[BlueGuitar]

Re: How to check pickup resistance and polarity?

What would those tests be?

Well, pull up a chair- this might take awhile! :smack:

Hopefully your humbucker is already wired up to 4 conductor cable... write down exactly how it is wired up and then disconnect all 4 wires. You can get color codes for most pickups here:

http://www.blueguitar.org/new/misc/pu_mfg_specs-sm.pdf

You've already mounted your neck and middle pickup so now you can start clipping the leads together to figure out which combinations work well and which don't. (If your guitar has a strat-like pickguard you might want to remove one of the tone pots and pull the pickup leads out through that hole for testing.) For testing you will want a cable that will plug into a guitar amp, but has alligator clips on the hot center conductor and ground shield.

Getting back to your humbucker, you can figure out which two leads go to each coil by tapping the screws or studs with a small screwdriver. You can check the polarities of the coil with a compass. You might decide to flip the magnet to change which coils will work with your neck and middle pickups respectively.

You do have at least one string strung up so that you can test that the coil combinations are in-phase as well as hum-cancelling.

BTW here is an excerpt from Seymour's FAQ:

How do I make an H/S/H guitar noise-canceling/hum-free?
In order for an H/S/H guitar to be noise canceling it is necessary to split the humbuckers in the #2 and #4 positions. Then you must make sure that the single coil in the center is both magnetically and electrically out of phase with the split coil from each humbucker. It can be done but for the layperson it can be a bit tricky. A far easier solution is to use a Seymour Duncan Stack®, a Vintage Rail or Duckbucker, or one of the Seymour Duncan single coil sized humbuckers.

 

[STRATDELUXER97]

Re: How to check pickup resistance and polarity?

Well, pull up a chair- this might take awhile! :smack:

Hopefully your humbucker is already wired up to 4 conductor cable... write down exactly how it is wired up and then disconnect all 4 wires. You can get color codes for most pickups here:

http://www.blueguitar.org/new/misc/pu_mfg_specs-sm.pdf

You've already mounted your neck and middle pickup so now you can start clipping the leads together to figure out which combinations work well and which don't. (If your guitar has a strat-like pickguard you might want to remove one of the tone pots and pull the pickup leads out through that hole for testing.) For testing you will want a cable that will plug into a guitar amp, but has alligator clips on the hot center conductor and ground shield.

Getting back to your humbucker, you can figure out which two leads go to each coil by tapping the screws or studs with a small screwdriver. You can check the polarities of the coil with a compass. You might decide to flip the magnet to change which coils will work with your neck and middle pickups respectively.

You do have at least one string strung up so that you can test that the coil combinations are in-phase as well as hum-cancelling.

BTW here is an excerpt from Seymour's FAQ:

How do I make an H/S/H guitar noise-canceling/hum-free?
In order for an H/S/H guitar to be noise canceling it is necessary to split the humbuckers in the #2 and #4 positions. Then you must make sure that the single coil in the center is both magnetically and electrically out of phase with the split coil from each humbucker. It can be done but for the layperson it can be a bit tricky. A far easier solution is to use a Seymour Duncan Stack®, a Vintage Rail or Duckbucker, or one of the Seymour Duncan single coil sized humbuckers.

Hey Steve....Gotta tell ya how lucky we all are to have another knowledgable guy on this great forum....You've sure helped me quite a bit years back when we were both on the Ampage...I still have alot of your very informational posts you wrote to me also..Welcome buddy!

John S.

 

[Artie]

Re: How to check pickup resistance and polarity?

Great post Steve. Even I get confused sometimes on the polarity/hum-cancelling issue.

This should go to the vault.

 

[roadsleeper]

Re: How to check pickup resistance and polarity?

Thanks for the info BlueGuitar!