Help with Seymour Duncan TB-4

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expat701

New member
Hi, I purchased a Seymour Duncan JB Bridge TB4 pickup some time ago for the bridge of one of my strats. I got it brand new, put it away and pulled it out today to install it.

I checked it with my multimeter before soldering it in and I'm getting some weird results.

I tested the bare/green and black wires with the red and white wires twisted together and i get DCR 6.74k. My understanding is that this is the way these pickups are meant to be installed if you are not using a push/pull pot to split the coils and yet the resistance is less than half what it's meant to be.

I then tried testing the seperate coils by measuring green and white wires but i get nothing. I then try measuring the black and red wires and i get nothing.

However if i test the white and bare/green wires with the black and red wires twisted together I get DCR of 13.6k.

The black wire is meant to be the "hot" however on this pickup it appears to be the white wire thats hot. What's going on? Could this be a manufacturing fault or am I missing something?
 
A Duncan pup should be green and red for the screw coil, and black and white for the stud coil. Try measuring that.
 
Separate all the wires, then use the continuity / circuit checker on your multimeter to check you haven't got a broken wire or a short.

Check all the combinations you can think of. Black and white should be a circuit, as should red and green, but any others indicate a short. If you don't get a circuit black to white and or red to green you've got a broken wire somewhere.

Next, measure the DCRs black to white, red to green.

The advertised DCR for the complete humbucker is 17.4 kohm, so you should see around 8.7 kohm on each individual coil..

If there's a broken wire you won't get a circuit at all.

If you've got a short that is somehow putting the coils in parallel, or if you've already misjoined wires to give you a parallel, you'll see around 4.35 kohms.

Remember two resistors in series = R1 + R2. Two resistors in parallel R = 1/[(1/R1) + (1/R2)]. If R1 and R2 are about the same, then resistance in series = twice the individual resistance, in parallel half the individual resistance.

​​​​​​​Last thing to check, I suppose, is that someone hasn't rewired the pickup in different colors. I once bought a used SD pickup that had been rewired to the Fralin color scheme.
 
The new person at the factory put pepper with their guacamole and salt with their salsa. They must not have completed basic pickup training.

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Yes, thats basically what I suspect. That said however even checking with the new "hot" white and bare/green wires i still only get DCR of 13.6k. this seems low for a JB bridge. Maybe the new guy had a hangover as well.
 
It's not impossible that a pickup could be mislabeled as well as miswired.
Where one mistake has been made, perhaps a second one isn't so unlikely...
If the dealer won't exchange it, I'd call Duncan and see what they say,
 
Yes, call Duncan. They will sort it out. It is rare, but sometimes weird things happen. We have discussed a few mistakes on this board before. If there is an error, I bet SD wants to know what it is so it can be fixed and prevented.
 
^ They're also jolly nice people and know that a happy customer is a customer who will come back for more stuff. That's why SD is my go-to brand for virtually every set of pickups I've bought, about a dozen in the last two years. Just a shame they don't do frequent flier miles...
 
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