Humbucker is humming, what to do?

[K-Frog]

When you say "blade" are you referring to the brass colored base plate or the flate plate running throught the center of both pickups that the pole piece are connected to?.

The pickup on the left has white paint on both sides.
The pickup on the left has no white paint on it at all (top or bottom).

btw, I really appreciate your help on this.

 

[SGD Lutherie]

When you say "blade" are you referring to the brass colored base plate or the flate plate running throught the center of both pickups that the pole piece are connected to?.

The pickup on the left has white paint on both sides.
The pickup on the left has no white paint on it at all (top or bottom).

btw, I really appreciate your help on this.

Yes, that is a steel plate that the magnets are stuck to.

The magnets on both side should be all facing the same way. So either the painted or unpainted side of all the magnets should be facing that plate that runs through the coils.

 

[K-Frog]

pickup on the right has no paint at all, so I can't face them the same way according to paint markings.

I did stick a magnet on the painted edge of the left magnet and it stuck. When I moved the magnet to the either edge of the right magnet, It was repelled.

Would that be correct for this arrangement?

The magnets are well stuck on the pickups

 

[K-Frog]

Also unwired them just now, and the faces of the magnets stick together, I suppose one is N and one is S, so turned around facing opposite puts the magnet faces aligned right NN>SS?

 

[SGD Lutherie]

Also unwired them just now, and the faces of the magnets stick together, I suppose one is N and one is S, so turned around facing opposite puts the magnet faces aligned right NN>SS?

They sound be S|S and S|S. Use the magnet with the paint as a guide.

 

[K-Frog]

I don't understand.

I'm using a magnetic pickup tool to test with, only one magnet pole exposed on the tool ( i have no idea if it's N or S).

It is attracted to the white painted edge of the left pickup, but repelled by it's face.

It's repelled by the edge of the non-painted right pickup, and attracted to it's face.


????

 

[Melik]

So I'm inferring it works then, right?

 

[K-Frog]

here's a pic of the assy without the pickup attached.

4 pole piece screws and 2 screws through the brass base plate up through the 2 "pole piece alignment bars"

Don't know if that helps with daignosis or not.

 

[SGD Lutherie]

I don't understand.

I'm using a magnetic pickup tool to test with, only one magnet pole exposed on the tool ( i have no idea if it's N or S).

It is attracted to the white painted edge of the left pickup, but repelled by it's face.

It's repelled by the edge of the non-painted right pickup, and attracted to it's face.


????

The white paint indicates the North pole. Ceramic magnets come painted that way. You want all the poles facing the steel plate to be the same, so the opposing poles are facing each other. They want to repel each other. Stick them to the plate. Both sides of the pickup must be the same.

So on both sides you want either the north or the south facing the plate. Since we could see white paint showing, we will assume the south poles of the magnets, on both sides, need to face that plate.

Also, if you removed the bobbins, you must put them back on the same way. If you flip them over they will be out of phase with each other and hum.

I'll post some pictures of my Gibson Mudbucker tomorrow.

 

[K-Frog]

ok, thanks

 

[MusicBear]

One basic detail that you have not (explicitly) mentioned:

(If it worked fine before you removed it from the original bass, and the pickup did not come apart during the transfer to the new instrument then there should be no reversal of magnetic polarity to adversely effect the humbucking operation.)

Have you checked to be sure that the output lead you are connecting to ground is the "ground" side of the pickup? It should be the lead that is connected to the pickup baseplate and cover. If that lead is erroneously connected to the "hot" side of the circuit then it will hum as you described in your OP.

Use an ohmmeter to verify which lead is zero ohms from the cover and baseplate. That will be your ground lead. The lead that is 30 K-ohms "above" the cover and baseplate will be your "hot" output lead.

 

[K-Frog]

It's a new pickup from "across the pond"

I'll verify that connection, or just reverse it for fun and see what I get

 

[SGD Lutherie]

One basic detail that you have not (explicitly) mentioned:

(If it worked fine before you removed it from the original bass, and the pickup did not come apart during the transfer to the new instrument then there should be no reversal of magnetic polarity to adversely effect the humbucking operation.)

This is true, but I was wondering if it was put together correctly at the factory. I once saw a set of humbuckers in a Yamaha SG-200 guitar that were wired up out-of-phase, so they were thin sounding and hummed.

Here's a late 60s mudbucker. I had rewound it at one point, so it has a lot less wire on it. Also the original magnets are not currently on the pickup. But this is how the real ones are put together.

Here I removed one bobbin so you can see the blade that runs through both of them. The pole piece screws are threaded into the steel bar on top. The wood on the bottom is just a spacer.

This is how the poles of the magnets should be facing on both sides. These are not the original magnets, but you get the idea.

 

[K-Frog]

Now I understand exactly the pole orientation you were trying to get me to understand

 

[K-Frog]

I just took a closer look at the magnets and this sucker is indeed assembled wrong. On the left side of my pickup assembly we easily see my white North poles (S poles facing the blade). The reason I don't see the white paint on the right side is because upon closer inspection, the white-painted North poles are facing the blade. :-(

Should i try to pull the magnets off and flip them around with the white N poles facing out like on the left side?

 

[SGD Lutherie]

I just took a closer look at the magnets and this sucker is indeed assembled wrong. On the left side of my pickup assembly we easily see my white North poles (S poles facing the blade). The reason I don't see the white paint on the right side is because upon closer inspection, the white-painted North poles are facing the blade. :-(

That's what I expected, since most ceramic magnets come with one pole painted. I couldn't figure why they would have mixed magnets!

Should i try to pull the magnets off and flip them around with the white N poles facing out like on the left side?

Yes. Make them all face the same way. They will stick to the steel OK, even though they want to repel each other, but I'd put a couple of drops of super glue on the blade first to keep them from vibrating or popping off.

You also want to make you you have the bobbins back on the way they were. If you flip one over it will be like winding it in reverse, and have phase the wrong way.

That should fix the hum problem. If it still hums that means a coil is on backwards. You can either flip it over or swap the wires going to the other coil. If you aren't sure which way they go on, try it out before gluing the magnets in place.

 

[K-Frog]

I'll try to do that tomorrow. Since the current magnets appear to be glued on, you got any suggestion on removing them?

 

[SGD Lutherie]

I'll try to do that tomorrow. Since the current magnets appear to be glued on, you got any suggestion on removing them?

Ceramic magnets are brittle and can break. I'd take a single edge razor blade and see if you can get it between the magnet and blade on the corner and then try tapping the razor with something and the magnet should pop off.

If the magnet should happen to break, you can glue them back together with super glue.

Obviously you only have to do one side.

 

[K-Frog]

I got the magnets off pretty easily today with no damage. When I get home with it I'll give it a try.

 

[K-Frog]

I got the magnets flipped over correctly, but it still hums.

It's reassembled and wired same as i got it, and it still hums.

I know i didn't put the bobbin back on wrong because it's near impossible (like putting a left shoe on your right foot, and backwards). The bobbin can't be flipped around end-for-end because the leads wouldn't reach. Although build rather symetrically, the outer side of the bobbin has the glue residue on it from the magnets, and I flipped them and put them on to match the other side.

What should I try now?
1) take the magnets off and flip the bobbin around, with the leads still on the same end, and put the magnets back on?
or
2) flip the bobbin end-for-end and extend the leads to i can connect them back together?

3) unwire the black leads that connect one side to the other and connect a red to black? Seems like i would be parallel then because I'm currently at 30k ohms with blk to blk wiring.

I can post whatever pics would be helpful to show where I started and where I am now, or whatever.

Just let me know what you think I should try next.