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Thread: Rewiring/upgrading Epiphone Les Paul - Grounding Question

  1. #1
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    Default Rewiring/upgrading Epiphone Les Paul - Grounding Question

    Hi everyone,

    I recently purchased an Epiphone Les Paul PRO/FX for the purpose of gutting and replacing all the electronics. The guitar has a Floyd Rose in it, and currently there is a very faint "crackling/popping" that goes away when I touch the strings.

    I have purchased new switches, jacks, pots, and Seymour Duncan pickups...Jazz for the neck position, and '59 Hybrid trembucker for the bridge. My hope is to wire this guitar such that the Jazz pickup in the neck position can be switched between series/parallel with its push-pull volume pot, and the '59 hybrid in the bridge can be switched between single-coil and humbucker with its push-pull volume pot.

    I have spliced together two wiring diagrams thusly:

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    While I'm a little intimidated, I think I can handle this job myself, and feel like I'm pretty confident about everything except the wiring of the switchcraft 3-way switch, and how that relates to grounding.

    My intent was to use vintage shielded wire, with the metal braided ground on the outside. I would plan to run three of them (1 long one to go from the switch's output to the guitar's output jack, and two shorter ones to run from the volume pots to the two inputs of the switch). I would then solder a jumper from the ground post of the switch, and use it to solder together all three braided metal ground sleeves. I plan to slide them all into a length of heat shrink tubing to bind them together tightly as they run from the switch to the guitar pot cavity...and then the two shorter wires' conductors would get soldered to the pot terminals, the longer wire goes on past the pots and gets soldered to the hot output jack tip and also covered with heat shrink so the metal braid cant touch anything hot and short circuit...but what do I do with the ground/shield for this long run of wires once I get into the pot cavity with them? I am lost, and am worried I will inadvertently create a ground loop.

    Since all three wires shielding are touching for quite some length, it is acting as one long ground wire. I could snip it all short just after it gets into the pot cavity, and solder the ground/shield to the back of one of the pots, where it would join the grounding circuit there, sort of as is shown in the above wiring diagram...but then the longer wire going on to the output jack would not have shielding. There fore should I not solder to one of the pots, and instead continue on with the shielding all the way to the output jack and solder it to the sleeve of that jack along with the ground wire coming from the grounding circuit of the pots?

    Maybe its best to bring the ground from the bridge, the ground from the pots, and the ground from the switch all three together at the output jack sleeve solder point?

    The grounds for the pickups will all be grounded to the backs of pots as shown in the diagram above.

    Any advice on how to wire this switch while prevent a grounding loop, noise/hum, and still keep the long runs of wires shielded would be greatly appreciated.

    Eric
    Last edited by HighDeaf1080p; 11-18-2015 at 11:56 AM.

  2. #2
    Member '87 sherwood's Avatar
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    Default Re: Rewiring/upgrading Epiphone Les Paul - Grounding Question

    Your plan sounds solid and well thought-out. Ground all three wires to the post on the switch with your jumper wire. Than when you enter the control cavity ground the one or all of the vintage braided wire to the back of a pot. The long output wire that goes to the output jack will get grounded at the jack and at the switch. Don't run every ground to the output jack since that will cause difficult mess to work with.

    When working with vintage braided push-back wire place some heat shrink near the end of the wire to prevent stray wire strands from the ground braid from touching the hot lead.

  3. #3
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    Default Re: Rewiring/upgrading Epiphone Les Paul - Grounding Question

    Thank you for the advice. Just to clarify...all three are grounded at the switch, all three are grounded again to the back of a pot, and then the longest one gets grounded a third time at the output jack ground?

  4. #4
    Mojo's Minions blueman335's Avatar
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    Default Re: Rewiring/upgrading Epiphone Les Paul - Grounding Question

    Basic rule:

    All electrical parts have to be included in the ground loop: PU's, pots, toggle, & output jack. Miss one and you get noise.

    If you have noise, verify all of those above have a ground wire, that it links into the ground loop, and that all of the solderings are firm (jiggle wires when plugged in). If everything can be traced back into the ground loop, there is no noise.
    Last edited by blueman335; 11-19-2015 at 07:41 AM.
    "Completely Conceded Glowing Expert."
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    Default Re: Rewiring/upgrading Epiphone Les Paul - Grounding Question

    But I thought there was a problem with anything having two paths to ground as would be the case in the above scenario. Is that not true?

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    Default Re: Rewiring/upgrading Epiphone Les Paul - Grounding Question

    Did it all today. It turned out brilliant!! I just ran the ground path for everything up to the switch and then down to the output jack to emilnate the possibility of any loops.

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    Default Re: Rewiring/upgrading Epiphone Les Paul - Grounding Question

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    Specifics of what I did:

    1. Routed a single conductor shielded wire from output jack up to the switch...grounded shielding at the sleeve of the jack, and at the ground lug of the switch.
    2. Routed a two conductor shielded wire from the switch down to the control cavity...Grounded shielding at the ground lug of the switch, and the back of the bridge volume pot. One conductor went to bridge volume, and one went to neck volume, terminal 3 on each.
    3. Ran ground wires from back of each volume pots to back of its corresponding tone pot, and then grounded out the center terminal of each tone pot.

    I also went with 50's wiring, and changed the location of the capacitor from the wiring diagram above, to achieve that.

    This provides one single path of grounding from any point in the grounding circuit, and I get dead silence on humbuckers, and a very subtle, warm and pleasant hum on the single coil (mostly only audible through headphones).

    Compared to the stock Epiphone alnico humbuckers (which I thought were very good), the tone is brighter, clearer, and far more detailed on both pickups, both positions. Because I used 50's wiring, and .022uf caps, the tone pots function quite a bit differently as well, from the stock modern wiring with the .047 caps that were in there.

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    Last edited by HighDeaf1080p; 11-23-2015 at 05:26 AM.

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