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  • Weird ground issue

    The stock passive MEC J pickups in my Corvette Standard fretless had the typical single coil noise issues. Standing at a certain angle would eliminate almost all the noise, the same way as my single coil Strats have always been.

    I swapped a set of Dimarzio Model Js in the other day. Love how they sound, but I'm getting insane ground buzzing. The Model Js are four-wire, and I have the black & white soldered together and taped, green to ground, red to hot. All the four-wire guitar humbuckers I've used always have a bare wire that goes to ground, but I think that's for the pickup's metal base plate, which the Model J does not have (a bare or a metal base). I've dealt with noisy pickups plenty of times, but here's where it gets a little weird.

    Sometimes, I can touch the strings, and the buzzing goes away. Touching the bridge doesn't affect it much. If I back off the master volume a little, grabbing the knob on the edges (and usually touching the grub screw) will make the buzzing go away, but a fingertip on top of the knob will not. Any sort of finger contact to the blend (middle knob) will kill the buzz. Touching the tone knob will not.

    This was what happened with the controls in completely stock form. This is my first experience with a blend knob, so I removed it, and wired it for standard 2 volume jazz wiring. Same thing: touching the neck volume only kills buzz when it's backed off a little, and not completely reliably. Touching the bridge volume kills the buzz, and touching the tone knob has no affect.

    I opened the cavity and found that touching the pot cases will eliminate buzz with either volume, but not as much as touching the middle pot's knob.

    Warwick's ground wire from the bridge is a thin, solid bare wire that goes from the bridge, and is soldered to each pot case. On my guitars, I always ran one wire shielded stranded wire from the bridge (or trem claw) to the closest pot, then another from that pot to the next, and so on for each component. Grounding the pickups to different pots makes no difference.

    I noticed when I touched the black and white soldered & taped wires, the buzzing increased. Since I'm not using any of the series/parallel or coil-splitting functions, on the neck pickup, I clipped the wires really close to the pickup's base, and re-soldered and taped them. No affect.

    Sorry for the novel length post, but I'm running out of ideas.

    Additionally, I plugged my PRS Custom 24 in with the same cable. When I activate the coil-tap, I got a little noise, but in humbucking mode, it's dead silent whether I'm touching the strings or not. We've only been in this house for about 6 months, and I recently swapped my music room with one of the kids' bedrooms, but with one guitar being silent and another noisy, I don't think the house's wiring is the issue.

    No dimmer switches in the house or anything, either.
    “I can play the hell out of a riff. The rest of it’s all bulls**t anyway,” Gary Holt

  • #2
    Re: Weird ground issue

    Your pickup color codes right so if anything this sounds like a string grounding issue.

    Hum can happen in a few places. This is how to check
    1) - pot to pot - in a straight line, no over lapping as in say on a strat going master volume and middle tone back.
    2) - string ground - strat tremolo claw (spring holder) , telecaster bridge and so forth - string ground can be attached anywhere
    3) - input jacks are polarized which means have to be in a specific way. This is easy.

    ground on the input jack is metal to the base. Sleeve, ground. I always say to myself SG like a Gibson. - ground
    plastic to the base on a mono input jack - hot lead.

    I was working on this guys copy of a James Hetfield explorer. The really cool headstock one. His string ground wire was not insulated. We soldered in some pickups and the guitar hummed. We put some heat shrink over the bare wire and it was fixed in his case. I like heat shrink for my insulation however electric tape can work if you're in a bind as it's overpriced in my local hardware stores.

    hope i could help answer your question

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    • #3
      Re: Weird ground issue

      Originally posted by shadowfire90 View Post
      His string ground wire was not insulated. We soldered in some pickups and the guitar hummed. We put some heat shrink over the bare wire and it was fixed in his case. I like heat shrink for my insulation however electric tape can work if you're in a bind as it's overpriced in my local hardware stores.
      This is the one thing I did not address. The ground wire on this guitar is a single bare wire going from the bridge to each pot. I'm going to replace it with normal, insulated stranded wire and see what happens.
      “I can play the hell out of a riff. The rest of it’s all bulls**t anyway,” Gary Holt

      Comment


      • #4
        Re: Weird ground issue

        Originally posted by shadowfire90 View Post
        Your pickup color codes right so if anything this sounds like a string grounding issue.

        Hum can happen in a few places. This is how to check
        1) - pot to pot - in a straight line, no over lapping as in say on a strat going master volume and middle tone back.
        2) - string ground - strat tremolo claw (spring holder) , telecaster bridge and so forth - string ground can be attached anywhere
        3) - input jacks are polarized which means have to be in a specific way. This is easy.

        ground on the input jack is metal to the base. Sleeve, ground. I always say to myself SG like a Gibson. - ground
        plastic to the base on a mono input jack - hot lead.

        I was working on this guys copy of a James Hetfield explorer. The really cool headstock one. His string ground wire was not insulated. We soldered in some pickups and the guitar hummed. We put some heat shrink over the bare wire and it was fixed in his case. I like heat shrink for my insulation however electric tape can work if you're in a bind as it's overpriced in my local hardware stores.

        hope i could help answer your question

        1) - "in a straight line, no overlapping". What do you mean? You're not talking about ground loops are you? Because that's a bunch of BS in guitar electronics.
        3) - No, no, no, no. There are NO "input jacks" in a guitar. And even the output jacks are not polarized. Maybe your microwave or sunglasses, but not a jack. You're right, it's "easy", just a hot and a ground (unless it's a stereo jack, then there will be two hots and a ground).

        "ground plastic to the base on a mono input jack - hot lead.". I hope you understand what you are saying because I sure don't. I know that there are some conductive plastics made, but not in any guitar components that I am aware of.

        It will NOT make any difference if a ground wire is insulated or not. Tell me how insulation (by its very definition is non-conductive) on any component will affect hum. Insulation is only necessary if it risks touching other electrical wires/components.
        Originally Posted by IanBallard
        Rule of thumb... the more pot you have, the better your tone.

        Comment


        • #5
          Re: Weird ground issue

          JB, You've been around long enough. You know the routine. Pictures! Lots of clear pictures showing every wire, connection, lug, pot, switch, jack, etc.

          I suspect some cold solder joints and/or poor ground connections, but pics will help.
          Originally Posted by IanBallard
          Rule of thumb... the more pot you have, the better your tone.

          Comment


          • #6
            Re: Weird ground issue

            ^ lol, how did I forget?
            “I can play the hell out of a riff. The rest of it’s all bulls**t anyway,” Gary Holt

            Comment


            • #7
              Re: Weird ground issue

              Also, it isn't that the strings pick up noise and this is transferred magnetically into the pickups and needs to be grounded. It's the opposite. The bridge, and the strings, are part of a chassis ground which provides more grounding to the circuit in addition to the main ground out the output jack, into the amp, into the earth.

              Last edited by Clint 55; 01-28-2020, 07:07 PM.
              The things that you wanted
              I bought them for you

              Comment


              • #8
                Re: Weird ground issue

                So, get this...

                The volume and tone knob have plastic shafts.
                “I can play the hell out of a riff. The rest of it’s all bulls**t anyway,” Gary Holt

                Comment

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