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Grounding hum issue


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I plugged in a guitar I use at work to teach lessons with and it started cutting out on me. No problem, I brought it home and found the ground wire was hanging on by a thread to the output jack. I resoldered it and then there was a loud hum that I had noticed from before I had fixed the guitar when I plugged it into my computer. I cut the wire back for both the ground and the hot (it's a combo wire with the ground wrapped around the inside insulated wire) and resoldered both. Still hummed when I plugged it back into my computer. I plugged in a similar guitar (both hh setups) and no such hum. I had already sprayed the output jack with contact cleaner. It was a little corroded, but it didn't seem like it needed to be replaced. I tried touching different parts of the wiring and I found that when I touch the knobs the hum would be reduced and when I touched the input jack where the cable came in and made contact with it, the hum completely went away. I'm not sure what to do and I don't want to start buying new components unnecessarily like a new output jack if it turns out that this won't fix my problem anyway. Any suggestions? Thank you for your advice. Have a great day.

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First of all, make sure it is not your amp or whatever. If you have a battery-powered amp, try that. Essentially, something that isn't mains powered. I get all kinds of problems here because of earthing issues in the house.

If that fails, use a continuity tester to confirm that the bridge is in good contact with the earthing, unplugged of course.

Is it possible that the wires on the jack are reversed? This can happen. Ask me how. ;-)

Is it the cable? Check another guitar.

Photos might help if you have good ones.

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If you can make the hum completely disappear by touching the cable at the jack socket, I'm willing to bet that your ground wire to the bridge is open-circuit. If you have a multimeter (even a cheapie from the hardware store) check continuity from the ground lug of the jack socket to your strings (should be 0 ohms if the ground wire is intact).

Other things to check are correct wiring at the jack socket (are the signal and ground lugs reversed?) or a break in the ground connection to the pots or pickups.

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  • 4 weeks later...

Hi, mi name is Juan Carlos, I'm a newbie at this fórum and I've felt free for asking my question in thisi topic because is something similar to Dalandser problema.I've built an explorer model of guitar but when I finally plugged it, I ended up with a horrible hmm noise that goes away completely when I touch strings or every metal part included strings.I point out:

-I've been testing in different equipments, amp, and amplitube on computer and the noisy is the same

-I've tested different guitars and others don't have this ground issue

-I've tested different cables

-I've tested the circuit with the digital ohmmeter and it may seem to be right

Following I enclose the diagram I've used and some pics.








In the Jack pic, the black wire goes to ground and the red one goes to tone pot and to switch

The pick ups are ceramic Gibson 496R (neck) and 500 T (Bridge)
I'm afraid I'm going insane.If someone coud help me I'd ve very grateful.Thanks for advance:

Juan Carlos

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It is worthwhile re-flowing each of the solder joints to ensure that there are no "dry joints". Since your multimeter reads 0 Ohms I don't think that this is the case though.

That is one of the best Explorers I have seen built for a while, Scorpionscar! I hope that you can get the hum figured out. Perhaps you should enter it in Guitar Of The Month :-)

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Did you ground all the pot cases together and the switch's body to the output jack? I don't see any jumper wires from pot case to pot case in your photo.


Edited by acpken
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