Classic Grounding Question: Hum Goes Away When I Touch Strings

C

cactus jack

New member
Here's a pic of my harness:

drDD513l.jpg


Here's the original diagram:

mDOY3xIl.png


The guitar is a rear route Strat with 3 single coils, Duncan SSL2 in neck and mid, and Duncan SSL6 in the bridge. The pickups sound great, and I'm very happy with the tone. However, if I'm not touching the strings, or other metal, there is significant hum beyond the expected 60 cycle hum. When I do touch the strings everything sounds like it should and I get the 60 cycle hum in positions 1,3,5, and it's dead quiet in 2, and 4. Remove my hand and I have loud hum in all positions.

Using a multimeter I have a great continuity from the output jack to the strings, between all three pots, I even grounded the switch since there is no pickguard.

In an attempt to fix this I have: Grounded the lug on the blender pot to the casing. I ran a jumper connecting all three pots, and I grounded the switch to the volume pot. I'm not sure what else to check. Any thoughts?
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

I’d un- ground the third lug from the blender pot and check all grounds for a cold joint. Good luck!
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Here's a pic of the cavity. Since the cavity is lined and everything is grounded to the volume pot I removed all the jumpers and separated the blender pot lug. I get perfect, 000 ohms, continuity readings between all components. The largest variance I got was 001 between the output jack and the G string. Again, the guitar sounds great, but the buzz has me begging for 60 cycle hum!

JoHdA5Hl.jpg
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Is the reddish wire your bridge ground? It might have become disconnected at the bridge. The problem sounds like a missing bridge ground with an SSS fender wiring that has a RWRP middle pickup, hence the buzz getting quieter in 2 and 4.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Problem solved!

After shielding the control cavity with no success I decided to pull the pups and shield those cavities too. Figured I'd might as well do it all since I had the tape handy. I got the copper in place, ran ground wires back to the main cavity, and soldered everything up. During the process I also grounded the metal pickup rings for good measure. I checked continuity across all cavities, rechecked every single connection. Bingo, bango, bongo!

Quiet as a church mouse. Wonderful 60 cycle hum where's it supposed to be, and dead quiet every where else. Oh, the wonders of guitar electronics. So deceptively simply and dastardly frustrating.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Hum is supposed to go away when you touch the strings... wrote an entire blog post about it. What you did is shield the heck out of that guitar which drops the noise level below the level of the actual signal but technically, it is still there..


Why? Because you are the source of the hum. you. Your body. You are, in essence, a big bag of water and function as an antenna. You emit the noise that the pickups and wiring pick up.

I wrote about this before. Dedicated a blog post to it.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

orpheo said:
Hum is supposed to go away when you touch the strings... wrote an entire blog post about it. What you did is shield the heck out of that guitar which drops the noise level below the level of the actual signal but technically, it is still there..


Why? Because you are the source of the hum. you. Your body. You are, in essence, a big bag of water and function as an antenna. You emit the noise that the pickups and wiring pick up.

I wrote about this before. Dedicated a blog post to it.
Click to expand...

I'm not familiar with your blog. If possible please provide a link as I'd like to check it out.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

^ That's friggin interesting that our bodies act as an antenna. I tested it yesterday when I was wiring with the control cavity open exposed to noise. When I brought my hands closer to the wiring, noise would increase, then decrease when I backed away. So we're getting grounded when we touch the strings! Could also some of the effect be that when we touch the strings we're adding to the bridge ground? Because adding the bridge chassis ground seems to decrease noise independent of being near the guitar.

OP: grounding your 5 way switch in addition to everything else will improve things a tad. Everyone leaves it out of the ground circuit for some reason.
 
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Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Yes Clint, I believe that is correct.

Your body can act as an antenna when it is close to the circuitry. But then acts as an additional ground when you actually connect to (touch) the guitar's ground (strings, bridge).
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

The trick is to remove your body while using the guitar. No antenna = no noise.

Similarly, many have thus far avoided the corona virus by not existing.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

By coating the control cavities with conductive paint or copper tape you reduce the antenna affect that your body may have on the electrical components.

Nagisa,
Your remark about the corona virus is not only irresponsible, but dismissive of the very real problem that we all are facing.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

It's not much of a problem for the people who don't exist.

For the people who do exist, it is.

I never said the corona virus doesn't exist. It does. Just not the people who do not exist. Because only people who exist, exist. As long as they can think. Or if you ask Nietzsche, as long as they exist.
 
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Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Thanks for the great info...excluding the Coronavirus stuff.

Regarding the switch, it becomes grounded once the copper tape is grounded. I bet a lot of folks go through the process of shielding their cavity or pickguard and never ground the darn stuff.

I'm officially a fan of shielding. I couldn't believe the difference it made, and made me appreciate good ole 60 cycle hum. I'll take hum over buzz every day that ends in y.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

I absolutely hate shielding, with a deep, intense passion. Why? I can hear the difference. Copper sheets, shielding paint... I can hear it and I don't like it :) I don't mind having hum when I don't touch the strings (which is rare, when I am playing the guitar). I can only see it as a problem if you play slide with a glass slide and use a humongous pick and don't rest your hand on the bridge. Odd technique, but only then I see 'my' way as a problem, haha!
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

cactus jack said:
Regarding the switch, it becomes grounded once the copper tape is grounded. I bet a lot of folks go through the process of shielding their cavity or pickguard and never ground the darn stuff.
Click to expand...

Christ. Yeah and their **** is noisy. You can't spend 5 minutes grounding ur switch and have it improve things??
 
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Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

Orpheo, I love ya.

But I love shielding tape more.

Any difference you can hear, doesn't make a difference when you're playing. Heck, it almost doesn't make a difference whether you play a LP or a Tele. Play what feels best in your hands and in your heart. The ears will take care of themselves.
 
Re: Classic Grounding Question: Hum Goes Away When I Touch Strings

I am pro-shielding, too. It sounds better without noise to me.
 
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