Grounding Issue

[JMC]

Hi everyone.

My guitar buzzes when I'm not touching the strings or any metal part of the guitar. As soon as I touch something metal, the buzz goes. It's not a loud buzz, but it's annoying and shouldn't be there.

It's an FS-1 kit, which is the same wiring as a Les Paul or ES335 - two humbuckers, two volumes, two tones and a three way switch.

I've tested continuity with the multimeter and can't find any issues. The buzz happens in all three positions (neck, neck/bridge, bridge), but reduces if I turn the tone all the way down. The volume and tone pots work as expected. The guitar tone sounds great. I just want to get rid of the buzz. Any hints?

Sorry if this has been asked before, but I couldn't find a similar post.

John.

[McCreed]

Did you run a ground wire to the bridge?

[JMC]

Yep. Ground wire was run to bridge. And I assume that it remains in working order because the multimeter shows continuity between the bridge and output jacks, pickups, etc.

[Drashkum]

Could be because of a cold solder of the ground on the back of your pots. Can you post a picture of the wiring and back of the pots that you may have before the assembly?

Sent from my NE2211 using Tapatalk

[fender3x]

...the multimeter shows continuity between the bridge and output jacks, pickups, etc.

1st thougt... You probably tested this as well...but does the multimeter show continuity between the strings and the output jack? Since touching any metal part calms the buzz, and since the multimeter shows that the metal parts and strings have continuity, it could be that they are all connected to each other but not connected (or have a cold solder connection as Drashkum suggests) to the ground that goes to the amp. You could also test this by plugging in a lead into the guitar, and touching the multimeter to the shaft at the other end of the lead and strings at the same time.

2nd thought...Do you get the buzz with any other guitars with the same type of pickups (humbucking vs single coil)? If the answer is yes you may want to check the ground on your amp. Or change the lead, which may not be well shielded. Or turn off any electric motors or fluorescent lights in your garage (maybe I mean in my garage ;-)

3rd thought...If this is a single coil guitar, does it buzz with both pickups engaged? That is often a humbucking mode...as you probably know...

4th thought... Is there anything you can take out of the signal chain that stops the buzzing? Sometimes it's a stomp box rather than the guitar that's causing the buzz. You may be grounding it rather than grounding your guitar when you touch the strings.

Like I said you've probably tried most of this stuff, but it's what I could think of.

[JMC]

Thanks Drashkum and Fender3x.

I've tested all four suggestions above. The guitar has humbuckers, with nothing in the signal chain apart from a cable (ie no pedals). I don't get a buzz using the same cable and amp. I suspect that I've got a cold solder somewhere and will pull each pot and resolder one by one.

We'll see if that solves it.

[fender3x]

One other thought...Is the cavity shielded? I am not sure that will end your troubles, but worth doing if you are in there anyway.

If you re-solder, start with the ground wire on the jack. Since you have continuity between the strings and the pots, the most likely culprit for a grounding issue at the jack. It could be somewhere else, but I'd start at the jack, then shielding...then every other ground.

Are there any other symptoms? Does it only buzz when the guitar is plugged in? Or do you hear the buzz without the guitar plugged in? Is it 50/60 cycle hum? Do you hear the radio? Is one pickup louder than the other?

[fender3x]

Here's an interesting article on the causes of hum.

https://www.prosoundweb.com/eliminat...ctric-guitars/

This shows the difference between an ignorant tinkerer like me and an EE. The issue of body grounding would never have occurred to me...

[Drashkum]

Here's an interesting article on the causes of hum.

http://https://www.prosoundweb.com/e...ctric-guitars/

This shows the difference between an ignorant tinkerer like me and an EE. The issue of body grounding would never have occurred to me...

Body grounding? U mean shielding the cavity and then soldering a wire from cavity to the back of the pot?.

I have done that on my strat build. And also I have a aluminium back plate on the pickguard of my strat so that gives the continuity on the pickguard as well.

I can vouch that shielding the cavity had made my strat totally quiet

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[fender3x]

I think if the guitar is well shielded the body grounding issue may be a moot point. I use aluminum HVAC tape on the back of my pickguards or covers, and to shield all around the inside of the cavity. The idea is to create a Faraday cage around the electronics so that they don't get RF interference. The "cage" should be continuous with the ground as Drashkum says.

What the article pointed out is that your body's proximity to the guitar also cause hum:

"When the guitar player touches the strings, does the hum stop? This indicates that the player’s body is acting as one plate of a capacitor.

The capacitance between the body and power wiring adds to the capacitance between the guitar and power wiring, increasing the level of the hum transmitted from the power wiring to the guitar."

The "cure" for this is to ground your body much the way you would wear an anti-static ground strap when working on sensitive electronics.

I am guessing this is not really an issue if the guitar is well shielded, but I don't know for sure. This is the first I had heard that I might be acting as one plate of a capacitor ;-)

(I noticed the link to the article was busted...hope it's fixed now)