Weird Issue with JB

[larryguitar]

I've got a G-spaced JB that was originally covered. I uncovered it and put it in a guitar where it worked fine and sounded just like a JB should.

I then pulled it and placed it in a different guitar, and the output was very, very weak; sounded like less than a single coil. Checked and double-checked my wiring, and finally pulled the pickup to check it out.

I pulled the four individual wires out of the potting wax and unsoldered them when I couldn't get a good reading from the leads, and what I found is that one coil (I don't have my notes with me as to which coil, or what the specific readings were, unfortunately) read a solid 8.8Kohms or thereabouts, while the other started out at 10Kohms and steadily dropped as I continued to meter it. It did this every time I checked it, which was more than five or six.

I expected to find a short or solder issue, but didn't expect something like this. Could it be a short in the coil? If so, why would the resistance go down like a battery discharging?

Not too upset about the dead P/U; I'm assuming it's my mistake that did this. Just trying to figure out what it could be.

Any pointers or advice would be appreciated,

Thanks,

Larry

[larryguitar]

Re: Weird Issue with JB

Rut roe...no ideas? I must really be out of my depth trying to figure this out if the uber-experienced pickup pros around this place don't have any ideas!

Larry

[CTN]

Re: Weird Issue with JB

never seen any pickup or coil do that with the dwindling resistance.

maybe call SD Customer service and ask them about it?

[larryguitar]

Re: Weird Issue with JB

Thanks, may have to do that. Like I said, more curious about it than anything, so didn't really want to bother SD. (It's not a customer service issue if I break it myself, right? )

[GilmourD]

Re: Weird Issue with JB

Sounds to me like something still isn't connected right.

Are you holding the pickup in your hand as you measure it? You might be heating it up subtly, affecting the already wonky reading.

[larryguitar]

Re: Weird Issue with JB

Sounds to me like something still isn't connected right.

Are you holding the pickup in your hand as you measure it? You might be heating it up subtly, affecting the already wonky reading.

No, I run out of hands. So the pickup is on the table, and I'm holding the wires up and pressing the MM leads to them.

And the measurements are from the (four) wires that are actually attached to the coils, so I'm not sure what could be 'hooked up wrong', since it worked fine before? My current guess is I poked the coil or something and it's got a very minor or intermittent short, changing its resistance as it shorts once the small voltage used to check the resistance from the MM is applied.

Or not. I'm not that sharp with all this stuff, and that plus curiosity will likely result in bad things happening to this pickup eventually.

Thanks!

Larry

[ehdwuld]

Re: Weird Issue with JB

are you holding the wires to the leads with your thumbs?
you could be reading your thumbs and not the broken pickup coil

a rising or lowering resistance
ticking up or down is what capacitors do
when checked by the meters small voltage ohm setting

what you proabably have is a broken coil or coil lead

may be fixable

remove the tape that surrounds the two coils



is it the screw coil?
that would be the coil with the black wire

the slug coil has the green wire

look at where the lead wires mate with the coil wires
test either end of the lead wires
to make sure the lead doesnt contain the break

test the start / finish of the coil
the wire is wrapped like a spool of thread
the start is where the wire first starts on the coil
and the finish is where it ends

if the break is in the coil then it is repairable only if it is near the finish wrap
a break at the start end is unrepairable without rewinding the pickup

is it in the coil?

remove the two screws that hold the coil to the base plate

look closer

[larryguitar]

Re: Weird Issue with JB

are you holding the wires to the leads with your thumbs?
you could be reading your thumbs and not the broken pickup coil

a rising or lowering resistance
ticking up or down is what capacitors do
when checked by the meters small voltage ohm setting

what you proabably have is a broken coil or coil lead

may be fixable

remove the tape that surrounds the two coils



is it the screw coil?
that would be the coil with the black wire

the slug coil has the green wire

look at where the lead wires mate with the coil wires
test either end of the lead wires
to make sure the lead doesnt contain the break

test the start / finish of the coil
the wire is wrapped like a spool of thread
the start is where the wire first starts on the coil
and the finish is where it ends

if the break is in the coil then it is repairable only if it is near the finish wrap
a break at the start end is unrepairable without rewinding the pickup

is it in the coil?

remove the two screws that hold the coil to the base plate

look closer

Wow, that's EXACTLY what I was hoping for, Sir! I will check those things and let you know how it turns out, but thank you very, very much!

[larryguitar]

Re: Weird Issue with JB

OK, finally an update. (I work too much!)

I finally stripped the pickup down to the coils, and read them directly; screw coil at 8.7, slug coil at 8.4. So there was a buggered connection somewhere in there, and resoldering it should sort it out. Will update when I have done that.

Thanks for the help, gents!


Larry