Tailpiece Grounding

[Lumberjack]

I'm having some ground hum problems with my Royale build. I've checked all the ground solder joints multiple times and they seem to be well connected to the output jack, but I still experience some hum. Once I put my hands on the strings or any hardware piece, the hum goes away! Is this normal for guitars with tailpiece grounding? Is maybe the tailpiece ground wire damaged?

There's a youtube video that shows the kind of problem I have right now:

https://www.youtube.com/watch?v=4jNexRg0jH8

My guitar's cavities are not shielded and the pickups are covered PAF style humbuckers.

 

[spauldingrules]

normal

 

[Lumberjack]

normal

I'm kinda baffled by this. I also have an Edwards Les Paul with cheaper pots, cables etc, no shielded cavities and no tailpiece ground wire, and it does not hum at all, with or without hands on the strings! So adding that tailpiece ground wire seems to make the touching of the strings necessary in order to eliminate the hum. Taking all of this into account, why would they add that tailpiece ground wire in the first place?

 

[Cagey]

If you have access to a multimeter, measure the resistance between the strings and the output jack housing. If it's anything more than 0 ohms, your bridge isn't as grounded as you think and your strings are acting like antennae.

Also, you don't need to have the cavities shielded, but it should be wired with shielded cable. If it's not, it'll pick up all sorts of noise. Even the 3" or so running to the output jack will pick up noise like it's priceless.

 

[Lumberjack]

I'm using shielded wire, not the standard shielded wire that Gibson and other guitar makers use, but it's still shielded wire and I've connected all shield to ground.

The ohm rating between strings and the output jack housing measures about 14 ohm. Does that mean that my tailpiece ground wire is loose or even damaged?

 

[Cagey]

The ohm rating between strings and the output jack housing measures about 14 ohm. Does that mean that my tailpiece ground wire is loose or even damaged?

Yes. That's low, but it should be a dead short. You may have to pull your bridge mounting post bushings out and re-do that run.

 

[Lumberjack]

I've rewired the guitar and I've shielded the switch cavity and the pot cavity with copper foil, but I still haven't replaced the tailpiece ground cable. The noise is gone now. I'm not sure if I should have soldered some of the ground cables directly to the copper foil? After all, everything's connected to ground in a properly shielded guitar... but maybe there's something that I've overlooked...

 

[Cagey]

The copper foil doesn't do much of anything, so it doesn't really matter. Besides, if the pots are mounted to it and they're grounded, then the foil is grounded. In any event, if the thing stopped making noise, then don't worry about it. That was the object of the exercise, right?

 

[BlueTalon]

With a reading like 14 ohms, I'm going to guess part of that conductive path is conductive shielding paint.  Some people swear by it, but it's an inefficient conductor, and a reading like that is typical.

I disagree with Cagey's contention that the copper foil doesn't do much of anything.  A good shielding job can go a long way toward reducing noise, depending on the source of the noise, and it appears that in your case, that's exactly what it did.  Still, I'd make sure the bridge is grounded.  Make sure your new copper shielding is grounded, too.