Identifying Grounding Issue

[BearBoy]

Is there any logic to hunting down a grounding issue in a guitar?

My JM Jaguar seems to have developed a really annoying buzz that I want to eradicate.

The facts (before Mezz hides them):

• Touching the strings, bridge and tailpiece does not seem to affect the level of buzz
• Touching the other metal parts of the guitar (i.e. the three control plates, pickup selector or metal part of cable) makes it disappear
• The buzzing is much louder with either the bridge pickup only selected or with both pickups in series
• Touching the pole pieces on the neck pickup also makes it much louder

Any ideas where I should start looking or is it just trial and error?

[James]

I don't know much about Jaguar grounding but I would just try and connect the bridge or tailpiece to the control plate.

The simplest looking way seems to be wrap a used guitar string around one of the bridge cups and run it to the control plate. You might have another issue but that will at least ground the bridge, strings and trem.

[robroe]

DEEP CUPS

[BearBoy]

Thanks James. You see, being a bit dim at this stuff, that is the last place I would have started (based on the fact that touching strings/bridge/tailpiece had no effect on the buzzing).

I am no electrical wizard, clearly.

[BearBoy]

DEEP CUPS

Just hoping those cups are DEEP enough to get them grounded.

[Dillon]

Thanks James. You see, being a bit dim at this stuff, that is the last place I would have started (based on the fact that touching strings/bridge/tailpiece had no effect on the buzzing).

I am no electrical wizard, clearly.

Actually I think I would agree with you, odds are the bridge is grounded. I don't know about VM Jags, but all the CIJ / MIJ, MIM, and AV Jags I've seen come grounded from the factory: there is a wire that runs from underneath the DEEP CUPS into the control cavity, usually screwed in to the body, or soldered onto one of the brass plates if present. I'd look for that, first. It sounds to me like one or more of the controls has lost its ground, as IIRC, that's how the plates are grounded from the factory---the controls are grounded, and since they're metal, and mounted to the plates, it also grounds the plates. It's been a while since I've looked at Jaguar electronics though so I could be completely wrong about that

[BearBoy]

Looking at the wiring diagram of the Johnny Marr Jaguar, it should have a ground wire running from the reverb handle/tailpiece area that then connects to the brass shielding in the volume/tone control cavity. The diagram doesn't show any grounding from teh DEEP CUPS. Would this be needed if the tailpiece was grounded?

If one of the controls has lost its ground, that at least should be easier for me to find and fix. Will need to get the screwdriver out.

[Dillon]

Looking at the wiring diagram of the Johnny Marr Jaguar, it should have a ground wire running from the reverb handle/tailpiece area that then connects to the brass shielding in the volume/tone control cavity. The diagram doesn't show any grounding from teh DEEP CUPS. Would this be needed if the tailpiece was grounded?

Nah, if the tailpiece is grounded it has the same effect, because the strings contact both bridge and tailpiece. I think the point is just to get the strings grounded somehow.

Come to think of it, though, if the bridge is not grounded, the noise should get LOUDER when you touch the strings. The human body is more a source of interference than anything---think of how touching the tip of the guitar-end of a cable (while it's plugged into an amp but not a guitar) causes it to hum. Bit of a mystery here, then, but it stands to reason that something isn't grounded properly.

I don't suppose you've changed anything in your setup? New pedals, new cables, even changed the location of the amp?