Wiring hummmmmmmmm

[Lostininverness]

Hi All,

I've finished wiring up a jazzmaster type build with dual humbuckers, 3 way all parts toggle switch and 2 concentric vol/tone pots. I've got a humming in various pick up positions. The humming drops away if I touch the pickups, pots shielding or bridge.

I used 4 core shielded wire from the switch to the pots, shielding paint in the cavity and tape on the back of the pickguard.

Bridge and control cavity are earthed to the bridge pot, along with the bridge pickup. The switch and jack are earthed to the neck pot. Both pots are eathed together via the middle lug of the tone part of the pot. (using vintage wiring)

I've also "jumpered" the outside lug of the vol part of the concentric pot to the middle lug of the tone part of the pot.

So used this plan for the "joining" tone and volume pots.

Humbuckers/3-Way Lever Switch/2 Volumes/2 Tones/Vintage

Basic guitar wiring diagram with 2 humbuckers, 3-way lever switch, two volumes and two tone controls. <strong>Click diagram image to open/view full size version.</strong> </strong> Ready to get started? Don't forget the <a...

guitarelectronics.com

All advice is appreciated - so frustrating! I want to get this sorted before I put the neck on and string it up.

Cheers
Grant

 

[Boreas]

Just for chuckles, re-flow the solder joint at the ground lug on the 3-way switch. That is a prime location for a cold solder joint.

Also make sure the switch contacts are clean and operating properly. Get down there and actually watch the contacts. I have had new switches where the blade/contacts did not work right and had to be tweaked.

 

[peterg]

^ +1

Please post pics of your work.

 

[pipthepilot]

You mention 4 core wire. Is that from the pickups as well?

The fact that its cancelling hum when you ground the bridge, would suggests that a short or cold solder joint isn't the issue. However, you should still check that.

If you have Humbuckers with 4 core wires, they can be coil split. If you have wired the incorrect start and end wires for either coils, they won't cancel each other out. This might be something to check. If they are the vintage style single core with outer shielded gnd it won't be the issue.

If you could post a pic of the wiring and the wire type for the PUs it will help to diagnose.

 

[Ronkirn]

yep. poor soldering technique is usually the problem.. if ya dare, give us a photo of it.. a good sharp one..

 

[schmee]

Does the pickguard shield ground to the electronics somehow?

 

[Telenator]

Your wiring diagram clearly shows a ground symbol coming from the negative side of the output jack.
Can you run a wire from the output jack to the bridge? That would take care of it.

 

[Lostininverness]

Hi team, thanks for the responses. I thought that I had it sorted earlier, but then something changed, and ......its baaaaccccckkkk.

I reflowed solder at the switch, didn't help.

I cleared the rats out of the nest that I've soldered, and here's some pics.

Bit hard to tell, but all earths lead to the bridge pot - from bridge, control cavity, 4 core shielded wire, switch lug, to the other pot and to jack.

I can run a wire easy enough from the jack to bridge - how will that work?

Cheers
Grant

 

[Telenator]

Hi team, thanks for the responses. I thought that I had it sorted earlier, but then something changed, and ......its baaaaccccckkkk.

I reflowed solder at the switch, didn't help.

I cleared the rats out of the nest that I've soldered, and here's some pics.

Bit hard to tell, but all earths lead to the bridge pot - from bridge, control cavity, 4 core shielded wire, switch lug, to the other pot and to jack.

I can run a wire easy enough from the jack to bridge - how will that work?

Cheers
Grant

You mentioned earlier that the buzz would stop when you touched one of the grounded metal parts on the guitar. The vast majority of electric guitars have a wire going from one of the pots, or jack directly to the bridge. When you touch the strings or bridge, the buzzing stops. You are a part of the grounding circuit.
As I pointed out earlier, the wiring scheme you posted clearly shows a "ground Symbol" coming from the output jack. You need to terminate that somewhere. Just make believe it says "bridge" right next to it and run a wire there.

 

[Boreas]

Hi team, thanks for the responses. I thought that I had it sorted earlier, but then something changed, and ......its baaaaccccckkkk.

I reflowed solder at the switch, didn't help.

I cleared the rats out of the nest that I've soldered, and here's some pics.

Bit hard to tell, but all earths lead to the bridge pot - from bridge, control cavity, 4 core shielded wire, switch lug, to the other pot and to jack.

I can run a wire easy enough from the jack to bridge - how will that work?

Cheers
Grant

If you have the bridge grounded to a pot that is indeed grounded, you shouldn't need to ground it at the output jack. But how is the output jack grounded? Is the + to the center and - to the shielded part of the wire? Is that wire to the jack shielded or just 2 strand? If it is shielded, how is it grounded? In other words, is it 2-strand wire with a shielded casing, or a single wire using a shield as negative? Sometimes shielded wire can introduce problems if not done correctly. Pix of the switch and jack may be helpful.

How exactly is the bridge being grounded?

In these cases, a cheap continuity tester is your best friend - especially one that beeps.

 

[Lostininverness]

You mentioned earlier that the buzz would stop when you touched one of the grounded metal parts on the guitar. The vast majority of electric guitars have a wire going from one of the pots, or jack directly to the bridge. When you touch the strings or bridge, the buzzing stops. You are a part of the grounding circuit.
As I pointed out earlier, the wiring scheme you posted clearly shows a "ground Symbol" coming from the output jack. You need to terminate that somewhere. Just make believe it says "bridge" right next to it and run a wire there. View attachment 1054733

Thanks for that. I've currently got a ground wire from the bridge to the back of a pot, which is also the same pot I've got connected to the jack. If I take another ground from bridge to jack will that create a ground loop?

One thing I was thinking of doing is removing the jumper between the vol and tone part of the pot and grounding each part separately. I'm not sure how it would make a difference, but will try it. Will reflow solder on the lugs of each pot while I'm there.

 

[Lostininverness]

If you have the bridge grounded to a pot that is indeed grounded, you shouldn't need to ground it at the output jack. But how is the output jack grounded? Is the + to the center and - to the shielded part of the wire? Is that wire to the jack shielded or just 2 strand? If it is shielded, how is it grounded? In other words, is it 2-strand wire with a shielded casing, or a single wire using a shield as negative? Sometimes shielded wire can introduce problems if not done correctly. Pix of the switch and jack may be helpful.

How exactly is the bridge being grounded?

In these cases, a cheap continuity tester is your best friend - especially one that beeps.

the shielded cable is only between the switch and the control cavity. And the shielding from that is ground to the back of a pot. The wires to the jack are just standard wires - one is the hot from the switch, the other is from the back of the pot.

Bridge is grounded using some shielding tape holding the exposed end of the ground wire to the body and the bridge screwed in place.

Yeah, I did a continuity test, and everything seemed right! I get continuity between all components - including the painted on shielding in the cavity. Thats why I'm so confused with the hum!

 

[Boreas]

Thanks for that. I've currently got a ground wire from the bridge to the back of a pot, which is also the same pot I've got connected to the jack. If I take another ground from bridge to jack will that create a ground loop?

One thing I was thinking of doing is removing the jumper between the vol and tone part of the pot and grounding each part separately. I'm not sure how it would make a difference, but will try it. Will reflow solder on the lugs of each pot while I'm there.

Ground loop shouldn't be an issue in a passive system. You do have allotta ground wires, and pot cases are notorious for cold solder joints.

But how is the bridge ground wire "attached" to the bridge? Just stuck under the plate? Sometimes the wire sinks onto the wood and can result in intermittent grounding. Someoyomes the plastic insulation makes the ground poor. Sometimes I will put a terminal on the wire or twist the copper into a loop to make better contact.

 

[Boreas]

the shielded cable is only between the switch and the control cavity. And the shielding from that is ground to the back of a pot. The wires to the jack are just standard wires - one is the hot from the switch, the other is from the back of the pot.

Bridge is grounded using some shielding tape holding the exposed end of the ground wire to the body and the bridge screwed in place.

Yeah, I did a continuity test, and everything seemed right! I get continuity between all components - including the painted on shielding in the cavity. Thats why I'm so confused with the hum!

Yeah - my head is starting to hurt as well...

If you get great continuity between the bridge and pots, I am most suspicious of the output jack. No errant solder or shielding? Could the jack be twisted in the cavity? Amp cable OK?? Cable fully inserted? [PureTone jacks click twice!] Amp OK?

 

[Lostininverness]

Ground loop shouldn't be an issue in a passive system. You do have allotta ground wires, and pot cases are notorious for cold solder joints.

But how is the bridge ground wire "attached" to the bridge? Just stuck under the plate? Sometimes the wire sinks onto the wood and can result in intermittent grounding. Someoyomes the plastic insulation makes the ground poor. Sometimes I will put a terminal on the wire or twist the copper into a loop to make better contact.

Yeah, you're not wrong about the number of ground wires!! The back of the pot is running out of real estate!

At the bridge, the plastic insulation is within the hole in the body with just the wire exposed. I then stuck some shielding tape over the fanned out wires to secure it to the body, then the plate stuck on it.

So do you recon I try reflowing the ground connections and see what happens?

If the hum stops when I touch any of the parts (pick ups, pots, bridge etc) does that give any indication on where the fault might be?

 

[Lostininverness]

Yeah - my head is starting to hurt as well...

If you get great continuity between the bridge and pots, I am most suspicious of the output jack. No errant solder or shielding? Could the jack be twisted in the cavity? Amp cable OK?? Cable fully inserted? Amp OK?

Will recheck the jack.

Yeah, the cable and amp are ok, I've checked by plugging in another guitar for "reference" of the floor level of hum.........

Bloody electrons!

 

[1stpitch]

Shouldn't there be a separate ground wire from the side of the bottom pot to common ground? They are 2 separate pots, IIRC.

 

[Boreas]

Yeah, you're not wrong about the number of ground wires!! The back of the pot is running out of real estate!

At the bridge, the plastic insulation is within the hole in the body with just the wire exposed. I then stuck some shielding tape over the fanned out wires to secure it to the body, then the plate stuck on it.

So do you recon I try reflowing the ground connections and see what happens?

If the hum stops when I touch any of the parts (pick ups, pots, bridge etc) does that give any indication on where the fault might be?

Usually it simply means a bad bridge ground - either at the plate or the pot. I am assuming the plate is conductive? With the plate screwed down, do you have continuity through to the output jack ground? Plug in your amp cable and see if you have proper continuity from the bridge to the negative side of the cable? Is there a switch position that works OK?

 

[peterg]

Is the bridge painted? If so the ground wire may not be connecting to the metal of the bridge.

 

[RobRiggs]

“I then stuck some shielding tape over the fanned out wires to secure it to the body, then the plate stuck on it.”

I’ve found some shielding tape isn’t conductive on the adhesive side. Worth a look.