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Jazz Bass Wiring Issue

H

hoshbrown41

Jun 19, 2009
178
0
#1
Sorry for the length. TLDR: control plate hum that goes away with human touch; loose wire off bridge pickup.

I was getting a lot of noise whenever I turned my tone knob up, but it would stop if i touched the control plate. Assuming it was a grounding issue or something similar, I opened 'er up and this is what I saw:

[Invalid or Expired Link Removed]

The wire I'm holding on to is just hanging around and not soldered to anything at the moment. :rollno:

Now there are a lot of wires going every which way, so here's a rough diagram I just made in paint. Just know I'm hardly an electrician, none of the intersecting lines are actual connections except at their endpoints, are the red lines are white wire. I'm not 100% on how they're connected to the PUs either.

Neck is to the left, controls are neck volume, bridge volume, tone, and then the jack.

[Invalid or Expired Link Removed]

Now my first question is if that dangling black wire should be soldered back along with the other black one (I think this should be obvious but want to be sure).

Secondly, why are there TWO black wires coming off my PUs? Nearly every diagram I came across before posting this showed one white, one black.

Thirdly, the only thing actually grounded to the plate in the cavity is at that one point off the neck pickups. Is that normal?

Finally: how can I fix the hum issue related to the tone/control plate that started this whole investigation?
 
#4
hoshbrown41 said:
Now my first question is if that dangling black wire should be soldered back along with the other black one (I think this should be obvious but want to be sure).

Secondly, why are there TWO black wires coming off my PUs? Nearly every diagram I came across before posting this showed one white, one black.

Thirdly, the only thing actually grounded to the plate in the cavity is at that one point off the neck pickups. Is that normal?

Finally: how can I fix the hum issue related to the tone/control plate that started this whole investigation?
Click to expand...

The extra wires might be grounded brass plates under the pickups. Did you confirm all three wires come from the pickups themselves? If so, they might be coil taps.

Do you have a bridge ground?
 
#5
MglMatador said:
The extra wires might be grounded brass plates under the pickups. Did you confirm all three wires come from the pickups themselves? If so, they might be coil taps.

Do you have a bridge ground?
Click to expand...

All the wires are coming from the PU cavities to the control cavity. My bridge pickup is grounded to the bridge (not one of the three wires diagramed).
 
#6
nice diagram!

you say touching the plate makes the buzz go away; does touching the strings do that as well? if not, your bridge is not grounded, and that needs to be rectified.

i'll bet you a quarter that black wire goes to ground; it's the bridge ground, or maybe ground for some shielding in the pickup cavity.
 
#8
How many connections do you have to your output jack? You only drew one wire.

Here's what I would suggest:

1) Find the jack ground - it's the sleeve connection to a regular 1/4" guitar cable. This should be the main ground point.

2) Tie your bridge ground to the main ground point.

3) Tie the backs of the pots together, then tie those to the main ground point.

Basically the idea is you don't want the control plate to carry the ground of the circuit: you want a soldered wire (or wires) to do the job. You can bridge from ground point to ground point with wire if you want, so long as each has a solid connection, and all such connections lead back to the main ground point.

I bet if you fix this your tone pot problem will go away too.

EDIT: and just to forestall all such nonsense, don't worry about star grounding anything.
 
#9
MglMatador said:
How many connections do you have to your output jack? You only drew one wire.

Here's what I would suggest:

1) Find the jack ground - it's the sleeve connection to a regular 1/4" guitar cable. This should be the main ground point.

2) Tie your bridge ground to the main ground point.

3) Tie the backs of the pots together, then tie those to the main ground point.

Basically the idea is you don't want the control plate to carry the ground of the circuit: you want a soldered wire (or wires) to do the job. You can bridge from ground point to ground point with wire if you want, so long as each has a solid connection, and all such connections lead back to the main ground point.

I bet if you fix this your tone pot problem will go away too.

EDIT: and just to forestall all such nonsense, don't worry about star grounding anything.
Click to expand...

There IS only one connection to the jack, and the only ground point is off the first volume pot.

The rest of what you're saying makes sense though.
 
#10
#12
Just found this:

[Invalid or Expired Link Removed]

Looks like those extra black wires were in fact grounds, which explains why the neck one is not attached and ergo not grounded.

So I just need to connect all the grounds, get one to the input jack, and make sure they all are connected to the body ground?

EDIT: So is the copper wire thats running from the bridge to the pickup even doing anything? Other than being an eyesore?
 
#13
first, resolder that one black wire to ground.

once that's done, you need to establish continuity between the bridge, that copper strip, and ground (if that one wire wasn't in fact it.)
 
#14
Yup. I removed the pickups and the tertiary wires were simply running back to the ground plates under the pickups. And lo and behold the copper wire that was grounding to the bridge had broken off the plate under the pickup.

Thanks walter :)
 
#15
"great success!"

borat-high-five.jpg
 
#20
hoshbrown41 said:
Cool, thanks. So I don't need that eyesore of a wire running from my pickup to my bridge then.
Click to expand...
you do unless there's another way of grounding the bridge, say with a hole drilled underneath it leading to the control cavity (the way they're all done now).

that strip was the way the vintage jazz basses did it, and i think it's kinda cool, like having the thumbrest down below the G string where it does no good. it's part of the vintage look.
 

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