Seymour Duncan JB over 300k resistance

[Ichabod]

Hello,
I have a Fender Stratocaster of a friend with a weird issue with this pickup a JB model in the bridge position.
It sounds thin, with a loss of low end, and it measures over 300k. Even now I have desoldered it from the guitar, so it's clear that it has something wrong.
What could I check to understand what's the issue?

 

[ehdwuld]

Coils

Check where the two coils connect
red white pair

Measure each coil should be around 8k per coil

Then reconnect the red white pair

 

[Ichabod]

Thanks.

I separated the red and the white wires.

The two coils north and south should be:
South -> Red and Green: 8.25k;
North -> White and Black: over 15M-16M.

So, the North coil has something wrong.
Is there a step two?

 

[freefrog]

Thanks.

I separated the red and the white wires.

The two coils north and south should be:
South -> Red and Green: 8.25k;
North -> White and Black: over 15M-16M.

So, the North coil has something wrong.
Is there a step two?

What you are experiencing is probably a "capacitive" coil: its wire is broken but stays aligned with itself. This break in the wire makes it behaves just like a capacitor.

If you measure(d) the capacitance of the pickup with its defective coil, it will/would probably exhibit around 4nF... And if the problem is what I evoke, the tone pot behaves strangely (= partly like a 2d volume control).

More explanations here: https://www.marshallforum.com/threa...ithout-anyone-noticing-it.130785/post-2343570

I've repaired my share of humbuckers with this problem.

One can try to unwind the defective coil in order to find where the wire is broken. It's possible but requires some care and... luck. Next step: rewinding the coil or changing it. Or change the pickup, or course...

Good luck in your tinkering.

 

[Ichabod]

White and Black wires measured 0.8nF, less than how much you said, but I think this change anything.

Meanwhile, I have to see how disassembly this pickup, I never do it.
Then, I guess if I am very very lucky the wire is broken close the begin, and I could even avoid the rewinding. Else I'm not sure if I really can rewind it in a safe and durable way. And I'm not sure... wax or other stuff like that... I could look at that, but I think I'm not going to do it.
I'm sorry for my friend, but the easy way, even if it will be the most expensive solution, is to buy a new pickup.

Thank you.

 

[freefrog]

White and Black wires measured 0.8nF, less than how much you said, but I think this change anything.

I realize my previous post was misleading: the 4nF that I've mentioned were just a typical / average value for the whole pickup in such cases, and not for damaged coils alone... and anyway, the measured capacitance in such a situation will obviously depend on the nature of the damage.

You're right, repairing a potted pickup with this kind of issue is a PITA. I've also solved it by changing the whole pickup the last time it happened. ;-)

Good luck again.

 

[playas]

If you are in the US it might be worth his while send it back to SD and paying to get it fixed.

 

[Ichabod]

I'm from Italy.

If I can repair it, somehow, my friend could mount it on a cheaper guitar.
In this Stratocaster a new pickup is a better choice.

 

[ehdwuld]

I would start on the easiest parts to get to

The internal winds are unlikely to be where the damage is done

Where the coil wires come out to the colored wire is the most likely area of damage

I would check and resolder at this connection

Check resistance after each attempt

 

[Ichabod]

I just open up the pickup. It's a bit sticky, of course!
Let me see if I can do something to clean the wires.



Else, I'll let it like is that now. Maybe I can set this pickup to be used permanently splitted. My friend is going to buy a newer pickup, perhaps a different model.

 

[freefrog]

The internal winds are unlikely to be where the damage is done

Where the coil wires come out to the colored wire is the most likely area of damage

I would check and resolder at this connection

Check resistance after each attempt

Your answer is logical but IME, the problem can also be in the first layers of wire : a high E string stuck under the top of a bobbin suffices to harm a coil. Another sensible area is the start lead, buried inside the coil and dying sometimes with time, for whatever reason...

 

[Ichabod]

I cut out the North coil, but the resistance is extremely high. It changes, but always over 10-12M.
I can't see what can I do, at this point. I don't want to take off the wax because it doesn't seem a good idea, and I can't re-wax it.

 

[ehdwuld]

you have a white and black wire going under the tape to the coil
lets look there

remove the tape

you cant damage it
it is damaged

plan D

Buy a new Pickup

lets stay with plan B
for now

it changes because thats where its broken
where the wires connect to the coil

 

[Chistopher]

Eddie Van Halen would probably love that pickup.

 

[freefrog]

I can't see what can I do, at this point. I don't want to take off the wax because it doesn't seem a good idea, and I can't re-wax it.

Since you've nothing to loose: don't hesitate to plunge the damaged coil in... boiling water. It should take out the wax superficially, giving easier access to the coil. It shouldn't cancel the benefits of wax potting.

Might sound scarry but I've done that more than once with separate coils and even with entire pickups. It has never damaged anything. But it made some urgent repair faster than with the tedious hair dryer process...

 

[Ichabod]

Sorry, I didn't answer for a long time.

My friend bought a new pickup. He still have the damage one, unlikely he will use it again just splitted (the only way to make it sounds ok).
Maybe in the future we can try some extreme solution to make it usable again.
Thanks!

 

[jeremy]

glad he got something working. if you wanna mess with the dead coil, we will be here to help

 

[Supernautilus]

Since you've nothing to loose: don't hesitate to plunge the damaged coil in... boiling water. It should take out the wax superficially, giving easier access to the coil. It shouldn't cancel the benefits of wax potting.

Might sound scarry but I've done that more than once with separate coils and even with entire pickups. It has never damaged anything. But it made some urgent repair faster than with the tedious hair dryer process...

The problem I’ve had with the hair dryer method is it seems not all wax is created equal. When I use it on SD pickups, the wax drips right out no problem. I assume this is because SD uses the “good stuff”. But I’ve tried to use a hairdryer on cheap pickups before and sometimes the stuff just doesn’t want to melt. Or else it partially melts and I have I scrape the rest out with a popsicle stick or something lol.