Guitar Grounding - Needing help

Ghostman

Ghostman

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Question: If I test with a DMM between strings, shouldn't I get 0 or close to 0 ohms? I have three guitars with tune-o-matic style bridges and all of them do not show a connection to ground when I test the strings, or between each string. One of my guitars, the bridge itself doesn't show ground, which I know I need to dive into it, but the other two, I have ground at the bridge, but not at the strings.

How do I remedy this?
 
Cadorman said:
Do you have a light hum that goes away when you wrap your hand around the neck?
Click to expand...
Yes sir. When I touch the cable jack, the hum goes away. So I broke out my DMM, and I have no connection between the strings and my ground. With my Schecter, there's a missing ground wire from the mounting post. With my Jackson and VMNT, I have ground at the post but that doesn't translate through to the bridge. I think there's some paint issues.
 
Ghostman said:
Question: If I test with a DMM between strings, shouldn't I get 0 or close to 0 ohms? I have three guitars with tune-o-matic style bridges and all of them do not show a connection to ground when I test the strings, or between each string. One of my guitars, the bridge itself doesn't show ground, which I know I need to dive into it, but the other two, I have ground at the bridge, but not at the strings.

How do I remedy this?
Click to expand...

between strings, shouldn't I get 0 or close to 0 ohms?

If the bridge itself is grounded, the strings might have continuity to the bridge.
Oxide can form on the strings and stop the continuity.

When you touch the 2 probes together, what is the meter reading?
 
Ghostman said:
Yes sir. When I touch the cable jack, the hum goes away. So I broke out my DMM, and I have no connection between the strings and my ground. With my Schecter, there's a missing ground wire from the mounting post. With my Jackson and VMNT, I have ground at the post but that doesn't translate through to the bridge. I think there's some paint issues.
Click to expand...

When I touch the cable jack, the hum goes away.

Even if the bridge / tailpiece is not grounded:
Shielding the inside of the guitar will stop the problem.

Single coil pickups are more of a problem than humbucking pickups.

The bridge / tailpiece does not need to be grounded if the inside of the guitar is shielded properly.
The guitar: is actually safer when the strings are not grounded.

So you will see some guitars that are built deliberately with no ground to the bridge or tailpiece.
This is OK when the shielding is done correctly.

FYI 2 layers of shielding is better than one layer.
Shielding paint and copper foil is a good choice. Aluminum foil is a bad choice.

 
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Amp Mad Scientist said:
When I touch the cable jack, the hum goes away.

Even if the bridge / tailpiece is not grounded:
Shielding the inside of the guitar will stop the problem.

Single coil pickups are more of a problem than humbucking pickups.

The bridge / tailpiece does not need to be grounded if the inside of the guitar is shielded properly.
The guitar: is actually safer when the strings are not grounded.

So you will see some guitars that are built deliberately with no ground to the bridge or tailpiece.
This is OK when the shielding is done correctly.

FYI 2 layers of shielding is better than one layer.
Shielding paint and copper foil is a good choice. Aluminum foil is a bad choice.

Click to expand...
The cavities are double shielded. It comes from the factory with shielding paint, and then I put another layer of Copper tape in the cavities.

The DMM reads 0 when shorting the leads together. I have a Bachelor's in Electronic Engineering. Not my first day with a DMM.

I misspoke above. When touching the strings the hum/noise does not go away. Only when I touch the guitar cable at the input jack. The hum isn't really bad, just more than I expected, and when I do touch the input jack, the hum goes completely away.
 
The post insert was yanked out and I put the ground wire in. Pulling this out was way easier than I thought.

okxBWzl.jpg
 
So apparently all three of my guitars have some grounding issue, and they are all different. My Schecter is almost dead silent now. I can run my gains as high as I want and I dont' get a ton of noise. I barely need a noise gate now. Boosted up front and all that jazz.

My Jackson, well, that's different news. It's quiet unless I place my hand above the pickup. If I touch the pickup, I get a ton of noise. Exactly opposite of what the Schecter used to be. It's a custom wound pickup from a forum member on a different site. It's a single Humbucker Soloist so when I palm mute, it screams and squelches like a little ..... well.

My Dean VMNT is almost quiet, but there's still a little bit of ground noise issues that go away if I touch various parts of the guitar.

At least one of them is now healthy.

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67plexi said:
I'm thinking it's in your amp if it's a PCB stray capacitance something to consider.

When I build my amps the last step is to chopstick all the high voltage leads until it's dead quite.

View attachment 60650
Click to expand...
Definitely something to consider but I've been chasing this noise issue longer than I realized. The Captor load box is what brought the problem to my attention since it highlighted the problem. I have three amps that I tested and the problems definitely lie in the guitars.
 
gball said:
I don't know anything about electronics/electrics, but a lot of Norlin-era Les Pauls have no ground to the bridge (my '79 doesn't) and they are about the most dead-silent guitars I have ever encountered, so maybe it never had a ground?
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There was no cable path to the bridge so it definitely came from the factory without a ground. However, after I put one in, it's dead silent now. So regardless if it was designed or not, it's a fix. :D
 
Kind of off topic, but I have found if you play wireless any guitar ground issues disappear. Makes it easy to determine whether it's the guitar or not. My bridge ground was broken on the V and I never had a problem. Then when I took it to the cabin a few weeks ago and had to plug in I had all sorts of hum that wouldn't go away. Luckily I have soldering equipment up there.
 
Ghostman said:
Yes sir. When I touch the cable jack, the hum goes away. So I broke out my DMM, and I have no connection between the strings and my ground. With my Schecter, there's a missing ground wire from the mounting post. With my Jackson and VMNT, I have ground at the post but that doesn't translate through to the bridge. I think there's some paint issues.
Click to expand...

If Schecter is equipped with EMG's there is no bridge ground.
 
Do you have a power conditioner some of the venues we play were built late 1800's dirty AC power'
At home a smart meter was causing noise through my guitar amps scoped the AC outlet spikes
Now I start at the power source and work my way forward just a process of elimination.
My friend Angus built and designed the major recording studios Angus said the first thing was isolation transformers and proper grounding 1950's through 1970's.
The 15A Furman power conditioner works well dirt cheap at $175.00

Furman power conditioner 001.JPG
 
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