Done wirning....a little hum.

[Matt Madden]

I wired this up last weekend. 84 Squier body, new GFS neck, new electronics, Seymour Duncan Little 59 and JB jr.

There is a slight hum, which stops when I touch the strings. There is a string ground wire to the bridge, but I'm thinking this is a ground or shielding issue. There is the stock shielding on the underside of the pickguard, which is grounded through the jack, I believe.

The way this string ground wire is set up, it is squashed between the body and the underside if the bridge. That's they way it came, so that's the way I did it. Maybe it should be soldered to the bridge?

Any advice on trouble shooting appreciated.

Matt

[Mark Swanson]

Don't assume something is grounded because it looks like it is, or looks like it should be. In other words, just because there is a wire under the bridge it may not be making a connection. The way to find out is with a VOM or a continuity tester...most meters have one on there. Go through all the wiring and make sure the meter tells you everything is grounded, and then we'll go from there.

[Matt Madden]

Thanks, Mark.

I will check it out.

[Peter Wilcox]

Are the pickup cavities shielded? And even if they are, are they making a connection to the shielding on the underside of the pick guard?

[Matt Madden]

I did not shield the pickup cavities. I did shield the control cavity. The inside of the pickup cavities is so rough, the copper tape doesn't stick very well (this is a stock body; I didn't route the cavities). I am realizing I should spend some time cleaning up the cavities and shielding more carefully, as well as checking all the connections.

Thanks.

[Mark Swanson]

Yes you need to check with some sort of a tester. If you have any shielding that is not connected to ground, it will actually do the opposite of what you want and act as an antenna that will pick up hum. So maybe you missed a connection, or something, it's easy to do believe me. And like I said it may look like you have a connection, but the tester will let you know if it's a bad connection.

[David King]

"There is a slight hum, which stops when I touch the strings."

This tells me that your strings are grounded. You've got two single coil pickups so with both pickups on full (in an ideal world) the guitar should be quiet or even completely silent. With just one pickup on then hum is normal and inevitable. If the hum gets louder when both pickup are on full then they are wound the same direction and their magnetic polarities are the same. You would need to flip both polarities of the wires and the magnets on one pickup to get the hum canceling effect we'd hope to see on a two pickup guitar. While shielding is a good and important thing it can't compete with the noise reduction potential of hum-canceling pickup configurations (which you may have but haven't stated explicitly).

[Matt Madden]

Thanks David. The pickups are actually both humbuckers (single coil size). You can't tell that from my bad photo, but they are.

I tested all the connections and found that the ground wire to the bridge was not a good connection. I also had some shielding that was not grounded. I think I have those things fixed. Everything else was good. I need to string it up and test it tomorrow since it is past my bedtime!

Thanks all!

[Chad McCormack]

Hi Matt. Just curious, what type of lighting (and light switch) do you have in the room where you are playing? We just installed 6 recessed can lights in our living room on a Lutron dimmer switch, and I get hum with those lights on if I'm running directly into my amplifier and not contacting my strings. It's way better when running through my pedal chain (gotta be some noise conditioning happening in one/more of my pedals I'd guess), but there's definitely some 60Hz hum happening when run direct. I've got humbuckers (StewMac Golden Age) with a coil cut on the neck position pup, but the hum persists regardless of coil cut toggle position if I'm not touching the strings and those lights are on. Just finished a build for my brother, actually, and we noticed it today... talk about annoying! Be sure to let us know what you come across to solve your problem!

[David King]

One common problem with house wiring is when the switched lead (typically black "hot") goes around the room to two different switches and the neutral (white wire) goes via a different path to the fixture. The result is a nice big loop and a very capable broadcast antenna of 60 Hz hum..