'57RI problem?

[bass dan]

Not sure if this is a problem or not. I have been doing my own tech work latley. I reinstalled the original pickup in my '57RI pbass. I had to resolder it a couple times as I had a cold solder. I have a hum if I touch the pole piece. Some of the poles hum more than others. Some wont hum if I am touching the stings some will.

I dont recall this being a problem before I started messing with it. It could be I never really toched the pole peices before and it has always done this but since I have messed with it I fear I messed it up.

The pickup sounds fine and ohms at 10.8k on my meter. I get a 11.5k reading at the output jack. Not sure if that is significant or not.

Maybe a problem with one of the pots or cap? Like I said I'm new to doing this but wanted to try. Any ideas?

[bassmanrocke]

Two thoughts. First it sounds like the ground strap for the bridge could possibly have come loose. I would check that solder joint first. The other is that if you disconnected the lead between the two halves of the pickup you may have reversed the leads and that would cause some buzzing issues as they would no longer work as a humbucker (polarity and winding direction issues).

[bass dan]

The ground maybe the problem. I didnt mess with the ground wire coming from the bridge but I have looked at wiring diagrams for a pbass. The ground goes to the volume pot but is not soldered to the wire coming from the pickup. It was like this before so I just duplicated the way it was. On the diagram I looked at the ground wire appeared to be soldered with the wire from the pickup to the pot. Right now they have separate solder joints on the same pot.

[Cadfael]

1.) The magnets in one coil hum more than in the other coil?
That's "natural". Same "problem" with a Jazz Bass ...


2.) Which amp do you use?
A battery amp without grounding can force these problems.
My Roland CUBE RX did until I soldered an extra ground wire for him.
Is the grounding in your house / the room okay? Does the problem occur in other rooms / houses, too?

3.) Do you have / can you get two small pieces of adhesive copper foil?
Solder small cables to them (one short, one long one). Connect the two foils via the shorter cable.
After soldering, stick them under the Magnets. Put the long cable to the electronic and solder it to Ground (pot housing). Touching the magnets then has the same effect as touching the strings - becasue they are both grounded then. No more humming ...

[SGD Lutherie]

Try reversing the polarity of the pickup (swap the hot and ground), or swap the two pickup halves (maybe, see below).

Here's what's happening; the start wire in the coil touches the magnets. The magnets are not grounded, so if the start wire on the pickup is wired to hot, touching the magnets makes an audible hum.

If you reverse the hot and ground, then the start wire is ground, and the noise induced in touching the magnets gets shunted to ground and you don't hear it.

The other coil will still hum however, since it's in series with the fist coil. Bit as long as the coil under the E/A string has the start at ground, it should be fairly quiet, since that's the coil that you would be touching most.

Alternately, you might have swapped the two coils. If you find you don't get any hum when you touch the magnets on the D/G coil, just swap the two of them without re-soldering anything. It doesn't matter which one is under which strings.

[bass dan]

Thanks for the advise. I dont think I have the pickup reversed because it has the raised pole peices on the A string. So I'm sure I have them in the right positions. I'll try the reversal of the hot and ground. and see if that does it.

All the pole peices make a hum if I touch them. Some louder than others. If I have my hand on the strings the hum goes away from some but not all the pole peices. The bass sounds fine but with the raised pole peices my finger hits them sometimes and makes a "thump" sound. Thats what got me touching all the pole peices.

[SGD Lutherie]

When you reverse the hot and ground one coil won't hum, but the other one will. Hopefully the coil that doesn't hum will be the one under the E/A, which is where you might rest your thumb.

Unfortunately this is just a poor design aspect of that type of pickup. Same is true with Jazz pickups. It's because the magnets are not grounded.

One thing you can try, is to stick some conductive shielding foil on the bottom of the magnets, and ground it. The problem what that however is it's hard to get it to make good contact with the magnets. I've seen conductive paint used on the Ken Smith Design pickups. That might work.

[bass dan]

Thanks. When I bought this bass it actually had tape on the raised pole peices. The bass probably did the hum before I messed with it. I dont really recall but since I've been under the hood I was checking and rechecking everthing. As long as I dont contact the pole peices it's no problem.

I still think I'll try the reversal of the hot and ground and see if it improves.

[Cadfael]

SGD was totally right with his descriptions.
But this only changes the position of the "humming magnets".

My method with the grounded copper (or brass) foils under the magnets stopps "humming magnets".
You should solder the foil first before sticking it under the PUs because the heat of a soldering iron near the coils / bobbins is something for experts.

I have never recognized or heard that grounded magnets change the sound.
In "Gibson type humbuckers" the magnets or screws often touch the grounded ground plate. With the grounded foil you do nothing else ...

The transparent tape on the magnets when you bought the PU was an "anti scretch foil" (like often on the pickguards).
But Tape on the PUs helps, when the PUs are very close to the strings and the strings sometimes touch the magnets (which gives a very unpleasant sound). They are also a "humming protection" but they don't "solve the problem itself.
The metal foil under them really solves the problem ...

[SGD Lutherie]

Originally Posted by Cadfael

SGD was totally right with his descriptions.
But this only changes the position of the "humming magnets".

My method with the grounded copper (or brass) foils under the magnets stopps "humming magnets".
You should solder the foil first before sticking it under the PUs because the heat of a soldering iron near the coils / bobbins is something for experts.

I have never recognized or heard that grounded magnets change the sound.
In "Gibson type humbuckers" the magnets or screws often touch the grounded ground plate. With the grounded foil you do nothing else ...

+1

[bass dan]

Just so I'm clear about this. These pickups do hum when you touch the pole peices. This is the way they are made. Unless you sheild the cavity you will always have some hum if you touch the pole peices.

I may have them installed correctly? I duplicated the way the Fralins were installed.

[SGD Lutherie]

Originally Posted by bass dan

Just so I'm clear about this. These pickups do hum when you touch the pole peices. This is the way they are made. Unless you sheild the cavity you will always have some hum if you touch the pole peices.

I may have them installed correctly? I duplicated the way the Fralins were installed.

As I mentioned last time, if the start of the coil (which touches the magnets) is connected to hot, you will hear hum when you touch the magnets. If the start of the coil is to ground, you wont. With a P bass you will have one that does not hum, and one that does.

You have to look at it as the two coils in series. Let's go left to right; with the start of the coil on the left, and the finish on the right.

On the start end you have ground, then the start of a coil, then the finish of that coil goes to the start of another coil, and then the finish of the second coil goes to the volume pot.

If the first coil has it's start to ground, the magnets will not hum when you touch them, but the second coil will no matter what. This is because the first coil's magnet's are near the ground side of the coil, and the noise is shunted to ground. The second coil however has its poles in the middle of what is like one big coil, so touching them will always make noise.

If the start of the first coil is to hot, then its magnets will also hum. That's what you have going on. So if you flip the polarity of the pickup, the start of one of those coils should now be at ground, and that coil should stop humming when you touch the magnets. But only one one coil. So that should be the one under the E/A, being that most people rest their thumb on it.

Now there can be a situation where the two coils were wound in the same direction, and then wired up start to start. That will hum no matter what you do, but that's not the normal way to wind a P pickup.

Incidentally, Fender winds the single coil pickups so the start (black wire) is ground to prevent the humming. On the Fender Mustang, you are able to switch the polarity of the pickups. because of that Fender used closed covers so that you could not touch the poles, and wouldn't get the hum.

Ideally the magnets should be grounded. That will stop the problem.

[bass dan]

got it. Thanks!

[bass dan]

Finally got around to trying to fix the hum. The ground from the bridge was not connected. Is that wire suppose to be soldered to the bridge? I pulled the wire easily out . I took the bridge off and could see there is no solder mark on it. Looks like it just may have been squeezed under the bridge.

Looks like I will be getting a new pickup anyhow. Both wires from the "E" side pickup broke when I was messing around with it. Does not look like a easy fix.

[Cadfael]

The ground wire is "never" soldered to the bridge.
It is just put under the bridge and then the bridge gets fixed.
Contact by pressing bridge onto the blank wire ...

[bass dan]

I thought that may be the case. Just making sure. Now I really wish I had'nt screwed up my pickup so I could have seen if thats all the problem was.

I ordered a '62 original Fender to replace it. I also got a "vintage" wireing kit from Stew Mac. Comes with 2 pots , input jack and wire. I figured to just start all over with the electronics on this bass.

[bass dan]

Just an update. I always like to give one when folks are kind enough to give me advise. Dropped in the new pickups, soldered the pots and input jack. All is well. In fact the bass sounds better than ever. Looking at the schematic I got with my wiring kit from Stew Mac the bass was never wired correctly to begin with.

Now the bass roars. Much better and defined low end, more harmonic goodness and better output volume. I feel kind of foolish for having played the bass for about 5 years in the condition it was in. I just had no idea how good it could sound.

Thanks for the advise.

[4Mal]

Sweet! I always like a happy ending.