ground problem

Clive Hugh

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I have just installed a pair of HB’s in a strat type guitar, when I touch the strings there is a loud grounding hum which becomes a squeal with the volume going up. Things I have noticed is when the front pickup is on there is a slight click if I tap the back pickup with a screwdriver and the reverse when I switch to the rear pickup. The hum is very minor if I only touch the metal jack plate. If I touch the bridge it is the same as the strings but if I touch the bridge and jack plate it drops down markedly. Any suggestions as the where I start looking.
 

Swirling Snow

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There should be a thin wire running from the spring claw to ground - often the switch but it might go all the way to the jack. If it's not there, you need one. :)
 

Clive Hugh

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There should be a thin wire running from the spring claw to ground - often the switch but it might go all the way to the jack. If it's not there, you need one. :)
Yes, it’s got that. I’m wondering if the blade switch is the culprit with that leakage (for want of a better word) from the pickup that is supposed to be off.
 

Steve Holt

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If you have a multimeter handy, take the pickguard off, and just start touching things. Place one end of the multimeter on the jack ground, and then start prodding around. The switch, the back of each pot, the claw, the strings, the bridge etc. should all be connected. That's a pretty quick way to see what isn't. Something like the claw could look like it's connected, but a cold solder joint could be the culprit.

Are the pickups potted? I think Squealing pickups and tapping noises is a sign of microphonic pickups, but I'm no expert on that. Or anything really.
 

Clive Hugh

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I have just run the multimeter over the pots, there are 3 pots with 3 lugs each and everything connects to everything else, all lugs to ground and to each other so with my limited knowledge of electronics I suspect there is a dead short some where. I am thinking to disconnect every wire and then put them back one at a time tillI get the short, is this the right way to go about it?
 

cousinpaul

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You might need a hotter iron to properly ground the wire to the claw and the braided grounds to the back of the volume pot.
 

dsutton24

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The bridge isn't grounded. Just because there's a wire and a solder glob doesn't mean there's continuity. Use your meter and check the resistance from the jack plate to all the metal surfaces of the guitar. You should see no more than a couple of ohms everywhere.
 

birdawesome

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Pretty much what others have said here. You know your bridge isn’t grounded because the hum should disappear when your hand touches the strings, and thereby completes the ground through you body.

Sounds to me like your wire isn’t continuous to the bridge, or that maybe it’s a cold joint that isn’t conducting well. I assume your pickups are grounded to the back of a volume pot, and that the pot is running to the bridge?
 

Clive Hugh

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Thanks guys, I have removed all the wiring, cleaned the backs of the pots and have started wiring all over. The solder on the claw will get done again as well.
 

Clive Hugh

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Wired it up as per the diagram from Seymour Duncan and exactly the same again. The claw solder was excellent. I did find out that the leads from the pickup pass current between the ground and hot lead, is this normal? I assume it is otherwise there would be no circuit. I have ordered new CT pots so I’ll try again in a few weeks. Another question, I have some solid core wire, the core measures 0.019” is this sufficient to use between the pots and blade switch?
 

Clive Hugh

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sorted it, I have no idea how, I resoldered all the joints, but it was the switch that was causing the problem, I replaced it and the problem eventually ceased, the schematic switch was wired differently so I just kept trying different lugs till it all worked.
 

Swirling Snow

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Another question, I have some solid core wire, the core measures 0.019” is this sufficient to use between the pots and blade switch?
Yes, the wire would be fine. There's virtually no current in a guitar, so workability is the key. It might be said because of vibrations the wire should be stranded, but Gibson's been grounding things with solid wire for nearly a century, now. Seems to work.
 

Clive Hugh

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Yes, the wire would be fine. There's virtually no current in a guitar, so workability is the key. It might be said because of vibrations the wire should be stranded, but Gibson's been grounding things with solid wire for nearly a century, now. Seems to work.
Thats a bit of good news for me because I used some of it and was worried if I’d done the right thing.
 




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