Grounding Problem (?) After Installing New Pots and Jack

[Uiah]

Hi,

I recently replaced all of the pots and jack in my Les Paul. Am getting sound and controls all work but overwhelmed with noise (as in as loud as the signal). Assume a grounding issue but not sure where I’ve gone wrong or if it’s possible to isolate. My soldering skills are sub-par so assume there’s a bad connection somewhere.

I have a multimeter but not quite sure how to use it to diagnose the problem. Is anyone able to give me some tips or look at my soldering to see if anything obvious stands out?

Pics in order are:

- Bridge volume
- Neck volume
- Bridge tone
- Neck tone
- Centre bit where jack joins?
- Jack connections x 2

Any help would be much appreciated.

[vintagekiki]

Female jack wiring wrong.
On female jack mutually swap hot and gnd places.

https://www.cigarboxguitar.com/knowledge-base/wiring-stereo-and-mono-jacks-for-cigar-box-guitars-amps-more/ ¹⁾

2)

[Uiah]

Female jack wiring wrong.
On female jack mutually swap hot and gnd places.

https://www.cigarboxguitar.com/knowledge-base/wiring-stereo-and-mono-jacks-for-cigar-box-guitars-amps-more/ ¹⁾

Great thanks mate, will swap them around. Much appreciated.

[Uiah]

Thanks for the reply. Jack was indeed wired around the wrong way. Rookie error...
While I’ve got you though (or for anyone else reading), still a slight bit of ground noise. Goes away when I touch the strings. Aware it could be the power, room etc, but is there any way to diagnose any bad connections, with a multimeter or otherwise?
Much appreciated.

[The Dude]

Usually buzz that goes away when you touch the strings is a bad or missing bridge ground. Check that the bridge is well grounded to the jack ground (sleeve) with a meter.

[Helmholtz]

The fact that the noise goes away when you touch the strings actually proves that strings and bridge are grounded.
Touching the strings grounds your body which is often the main source of electrical noise.
Just touch the tip of your guitar plug or the the probe of a scope to hear/see how much noise voltage your body collects from the environment.

As far as I can see, only the bottom of the cavity is shielded. Good shielding requires shielding of all cavity sides, including cover and pickguard (think Faraday cage). But it's rarely done.

[Fluoroscope 5000]

The fact that the noise goes away when you touch the strings actually proves that strings and bridge are grounded.
Touching the strings grounds your body which is often the main source of electrical noise.
Just touch the tip of your guitar plug or the the probe of a scope to hear/see how much noise voltage your body collects from the environment.

As far as I can see, only the bottom of the cavity is shielded. Good shielding requires shielding of all cavity sides, including cover and pickguard (think Faraday cage). But it's rarely done.

Somebody else might know for sure, but I think it indicates that the strings aren't grounded through the guitar wiring if the noise reduces when you touch the strings. Wouldn't that mean the strings are being grounded through your body (assuming your body is not fully insulated from the earth)?

I'd be curious to hear a proper example of the noise b4 and after cavity shielding with fully hum-canceling pickups (many HB's are not fully hum-canceling). As long as all the + & - wire pairs are twisted, and the component chassis are all grounded, would shielding make an audible difference? I shield the control cavities anyway, but not the pickup cavities because I don't see how it makes any difference as long as the leads are twisted. Of course, SC hum would be much louder than other extraneous noise.

[Helmholtz]

Somebody else might know for sure, but I think it indicates that the strings aren't grounded through the guitar wiring if the noise reduces when you touch the strings. Wouldn't that mean the strings are being grounded through your body (assuming your body is not fully insulated from the earth)?

No.

As said, the player's body is the main source of electrical noise in a guitar - if not grounded to guitar or amp.
Connecting a scope to your body shows the noise voltage you are carrying.
Reason is that a body is a big capacitor or antenna that collects noise from the environmental fields.

When the player touches the grounded strings or any other grounded point that is connected to the amp, the noise stops because the noise voltage on the body gets shorted to amp ground. And a grounded body acts a a shield.
When strings are not grounded, the noise might even increase when the player touches them.

BTW, it's easy to measure if strings are connected to ground or not.

[Uiah]

Usually buzz that goes away when you touch the strings is a bad or missing bridge ground. Check that the bridge is well grounded to the jack ground (sleeve) with a meter.

Thanks Dude for the reply. I'm measuring about 6.5ohms between jack ground and strings, or around 8ohms between bridge volume pot and strings. Is this too much? Would that be a bad solder joint where the bridge ground connects to the pot (didn't touch the other end).

String noise is definitely more than before I did the upgrades.

Much appreciated.

[Fluoroscope 5000]

No.

As said, the player's body is the main source of electrical noise in a guitar - if not grounded to guitar or amp.
Connecting a scope to your body shows the noise voltage you are carrying.
Reason is that a body is a big capacitor or antenna that collects noise from the environmental fields.

When the player touches the grounded strings or any other grounded point that is connected to the amp, the noise stops because the noise voltage on the body gets shorted to amp ground. And a grounded body acts a shield.
When strings are not grounded, the noise might even increase when the player touches them.

BTW, it's easy to measure if strings are connected to ground or not.

Well, I'll be snookered. I took the liberty of testing this idea by disconnecting the ground on one of my guitars, and the noise was indeed slightly higher when touching the strings. I only wish I had thought of touching a wall socket ground screw while touching the strings to see if the noise would lessen.