DC resistance reading - J-Bass pups

[SGD Lutherie]

Originally Posted by El Tedesco

I think this is confirmative and comes closest to answering the objective question. For installed pups, anyways.

Here is what I observed, J-Bass 2 Volume, 1 Tone
Measure the wire at the volume solder point with both pots fully open results in each pup reading 1/2 it's value.
As soon as I close one volume pot, the one that remains open doubles the value.
This makes sense.

Still, my readings on uninstalled pups are exactly 1/2 value on each.
There's got to be something about J-Bass pups being designed, unlike other pups. At least that's what it's hinting at.

If you have a volume control on 10, you can get nearly the exact reading on a pickup. It's very close to the actual number. Having one volume control up and the other on zero should allow you to take a reading on each pickup.

I've done this a number of times when I can't unsolder a pickup, and want to get a quick reading for trouble shooting purposes.

As an example, if you have two 250k resistors (pots) in parallel with a 9k resistor (pickup), you will get 8.3955k. So you can see that it's not too far off. I didn't count the tone pot since the cap blocks DC.

[El Tedesco]

Originally Posted by SGD Lutherie

Those figures seem too low.

That's what I am after. An answer to the fact that I am getting a reading of 1/2 value DC resistance on my J-Bass pups, unlike my guitar pups.

It is likewise the same reading results, installed and uninstalled.

[El Tedesco]

Originally Posted by SGD Lutherie

If you have a volume control on 10, you can get nearly the exact reading on a pickup. It's very close to the actual number. Having one volume control up and the other on zero should allow you to take a reading on each pickup.

I've done this a number of times when I can't unsolder a pickup, and want to get a quick reading for trouble shooting purposes.

As an example, if you have two 250k resistors (pots) in parallel with a 9k resistor (pickup), you will get 8.3955k. So you can see that it's not too far off. I didn't count the tone pot since the cap blocks DC.

Thank you for this statement, that's exactly what I am looking at.
But how about those MIM J-Bass ceramic pups (uninstalled) reading ~ 5 kohm. That can only be 1/2 value.

[maturanesa]

If ALL of your pickups read a half it would indicate THE PICKUPS ARE FINE... I dont think you have all defective different brand pups...It´s just the way you are reading them...must be wrong..

[El Tedesco]

Originally Posted by maturanesa

If ALL of your pickups read a half it would indicate THE PICKUPS ARE FINE... I dont think you have all defective different brand pups...It´s just the way you are reading them...must be wrong..

That's exactly what I was thinking. The reading pattern is the same every time and the way I measure them is the same every time. As I stated, my guitar pups read as indicated by the manufacturer.
If anybody could tell me what I could be doing wrong, measuring those J-Bass pups and I can verify that, I would greatly appreciate it.

[line6man]

Originally Posted by El Tedesco

Thank you for this statement, that's exactly what I am looking at.
But how about those MIM J-Bass pups (uninstalled) reading ~ 5 kohm. That can only be 1/2 value.

Is that not exactly what I said in post #12?

[El Tedesco]

Originally Posted by line6man

As you have noted, placing two pickups of similar DCR in parallel decreases the total DCR to about one-half. When you measured both pickups in parallel while they were wired up, did the DCR drop to approximately one-quarter of the rating for one pickup? Since you have described that the DCR of each pickup is one-half its rating when measured alone, the total resistance should drop to approximately one-quarter of the rating, if both pickups have an approximately equal DCR, when they are wired up in parallel in the circuit.



Righteousness? What was beside the point?

What you said was:


The first paragraph of this statement is the reason for the third paragraph, in this context. That being said, it is very difficult to understand what exactly you are doing, because without further clarification on your methods of measuring the DCR, the behavior you have described either points to you having improperly measured the DCR of a coil in a parallel circuit, with the results supporting the physics of a parallel circuit, or you have pickups that defy the physics in an extreme way. The former is much more plausible than the latter.

Ok, let me simplify the question to the bare bones. How is it that my uninstalled J-Bass pups read 1/2 value when measuring at the lead wire?

[El Tedesco]

Originally Posted by line6man

Is that not exactly what I said in post #12?

In a way, yes. But you focused too much on the pot's resistance, that's why it didn't come across clear enough.
However, Lutherie in #21 provided a direct example of how the pot's resistance effects the resistance reading on installed pups.

[megafiddle]

Originally Posted by El Tedesco

I think this is confirmative and comes closest to answering the objective question. For installed pups, anyways.

Here is what I observed, J-Bass 2 Volume, 1 Tone
Measure the wire at the volume solder point with both pots fully open results in each pup reading 1/2 it's value.
As soon as I close one volume pot, the one that remains open doubles the value.
This makes sense.

Still, my readings on uninstalled pups are exactly 1/2 value on each.
There's got to be something about J-Bass pups being designed, unlike other pups. At least that's what it's hinting at.

On my MIM Jazz bass, in circuit pickups read 5.1 K for the bridge and 5.2 K for the neck when they are on individually.
With both on (both volumes at '10'), I read 2.6 K.
So if measured out of the circuit, actual value of each would be around 5.5 K.

I assume you are getting similar results for your installed pickups? You get a little less than rated value when each is
selected individually with the volume control, and about 1/2 when both are selected?

Measured out of the circuit, you should read the rated DCR as you know. There is nothing more than a very long
piece of wire involved. If the measured value really is 1/2 of what it should be it is either shorted, or underwound
(assuming it's single coil).

If your meter were the problem, it would be intermittant, as some of your results are as expected. But since you
repeated the measurements many times with the same results, it kind of rules out a meter problem. Intermittant
problems would be more random.

If you really want to be sure, you could pick up a 4.7 Kohm resistor from Radio Shack. The standard, lower priced
5% carbon films are plenty precise enough as related to this particular problem. That will tell you pretty quick if the
meter is reading correctly.

But at this point, it sounds like it's the pickup.

[megafiddle]

Originally Posted by El Tedesco

Thank you for this statement, that's exactly what I am looking at.
But how about those MIM J-Bass ceramic pups (uninstalled) reading ~ 5 kohm. That can only be 1/2 value.

Just saw that post - I don't know if mine are ceramic, but if they are, ~ 5K is correct.

[El Tedesco]

Originally Posted by megafiddle

On my MIM Jazz bass, in circuit pickups read 5.1 K for the bridge and 5.2 K for the neck when they are on individually.
With both on (both volumes at '10'), I read 2.6 K.
So if measured out of the circuit, actual value of each would be around 5.5 K.

I assume you are getting similar results for your installed pickups? You get a little less than rated value when each is
selected individually with the volume control, and about 1/2 when both are selected?

Measured out of the circuit, you should read the rated DCR as you know. There is nothing more than a very long
piece of wire involved. If the measured value really is 1/2 of what it should be it is either shorted, or underwound
(assuming it's single coil).

If your meter were the problem, it would be intermittant, as some of your results are as expected. But since you
repeated the measurements many times with the same results, it kind of rules out a meter problem. Intermittant
problems would be more random.

If you really want to be sure, you could pick up a 4.7 Kohm resistor from Radio Shack. The standard, lower priced
5% carbon films are plenty precise enough as related to this particular problem. That will tell you pretty quick if the
meter is reading correctly.

But at this point, it sounds like it's the pickup.

Thanks for that info. This is very helpful. Seems I getting somewhere. My MIM pups are uninstalled, but read very similar in the low 5's.
I was assuming they are a lot higher resistance and hotter wound then that.
The custom set went into the J-Bass instead of the MIM's, but I do remember they read uninstalled in the 4's whereas they should be in the 8's. The pickup winder indicates 8.8 and 8.4 kohm. I will verify the reading later tonight with proper setting of the volume pots.

In line with my earlier statement (below) the Am Stds are installed and I was reading with both volumes fully open.
The MEC are also installed and I read with the blend knob fully open turned to the respective Pup. If the blend knob is center either pup will read 1/2 value. Now, as it shows, they are reading 1/2 value, when both volumen pots are fully open and full value (minus pot resistance) when 1 volume is closed and 1 fully open.
Sweet confusion. But I think I have it sorted out now

Originally Posted by El Tedesco

They are all single coils.
American Std J-Bass Alnico V
3.6 Neck, 3.6 Bridge
MIM Std J-Bass pickup Ceramic
5.0 Kohm Neck, 5.2 Kohm Brigde
MEC Dynamic Correction (Warwick Corvette)
9.3 Kohm on both with the blend knob fully open on either Neck or Bridge These seem to be the only correct reading, although I have no reference on their value, they are hot, ergo could be 18 kohm each.

I also have a custom set that is per winder's specs in the low 8's for the Neck & high 8's for the Bridge, both read about 1/2 value (4's)

Somebody help me solve this mistery!

[P Town]

Are you using a good CALIBRATED meter?

[El Tedesco]

Originally Posted by P Town

Are you using a good CALIBRATED meter?

It's an ok meter, but yes it's calibrated. We eliminated the meter issues already, as the readings are too consistent to indicate meter issues.

[megafiddle]

It looks like all the installed measurments are reading as the should.

I think the problem now is just any uninstalled pickups that are reading 1/2.

Alnico magnets, especially the older grades, are not very powerful. With the more powerful
ceramic magnets, less turns are needed for the same output. So these tend to be lower resistance.

[El Tedesco]

Originally Posted by megafiddle

It looks like all the installed measurments are reading as the should.

I think the problem now is just any uninstalled pickups that are reading 1/2.

Alnico magnets, especially the older grades, are not very powerful. With the more powerful
ceramic magnets, less turns are needed for the same output. So these tend to be lower resistance.

Well the only set currently in uninstalled condition are the MIM ceramics, which you measure within the same Kohm range as I do.
I didn't think they are that low in output.

What bugs still bugs me, is that the custom set I installed in place of the MIM's read 1/2 of what they are supposed be, before intallation. But I will read those again later tonight. As they are now installed, I will incorporate the learned issues.

[maturanesa]

why dont try this (measure from the cable with circuit installed):

http://www.youtube.com/watch?v=9Jcb7...fSoGw&index=42

[megafiddle]

Originally Posted by El Tedesco

Well the only set currently in uninstalled condition are the MIM ceramics, which you measure within the same Kohm range as I do.
I didn't think they are that low in output.

What bugs still bugs me, is that the custom set I installed in place of the MIM's read 1/2 of what they are supposed be, before intallation. But I will read those again later tonight. As they are now installed, I will incorporate the learned issues.

I'm not sure how you are measuring installed pickups, but I just plug in a cord and probe the free end.
If you know how the controls are set up, you can measure not only pickups, but volume control value
and even the pot taper, (linear or logarithmic).

You don't need to probe the individual pickup inside the bass. When you select a pickup and turn it's
volume all the way up, and turn the other pickup's volume all the way down, you have connected the
pickup directly to the output jack. And you can read it right there at the end of a connected cable.

And as you already know it will read a bit lower than it's actual resistance, due to the control pots.

Resistance is often equated with output. This is true if all else is equal (same magnets for example).
But ceramic magnets are more powerful. They do not need as many turns to get the same output
as an alnico pickup, and so the resistance will be lower. Less turns, less wire, less resistance.
Now if those 5K pickups were alnico magnets, then the output would be less.

[El Tedesco]

Ok, I measured the custom set installed in the MIM J-Bass and it does read 7.8 khms on the neck pup with the volume fully open and the bridge volume closed. That would be in line with the winder's specs of 8.3 kohm.

I don't know what happened when I measured them uninstalled. But that's ok.

Thanks all for your input and helping to narrow the issue down.