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I recently bought an old electric guitar (an SG copy) on eBay, as a little restoration project. I have some basic experience with electronics from university, but that was 15 years ago and I've never worked on a guitar before.

There's no sound from the neck pickup. I got out my soldering iron and multimeter and checked each component individually - the switch, all four pots and both pickups look to be working fine. While doing that I noticed something strange about the wiring, and I think there's a ground connection missing.

The existing wiring mostly matches the wiring in the diagram shown below, just with the bridge and neck pickups swapped. The ground from the bridge is soldered to the bridge volume pot, which has a wire connecting it to the bridge tone pot, which is further connected to the neck tone pot, grounding each of those three pots. But unlike the diagram, that's where it ends - i.e. rather a ground connection joining all four pots as in the diagram, the neck volume pot (in the position of the bridge volume pot on the diagram) seems to be ungrounded. wiring diagram (found on sixstringsupplies.co.uk).

  1. Am I correct in thinking this would explain the lack of sound from the neck pickup?

  2. If I add this final ground connection, is there anything special that I need to keep in mind with the choice of wire? Or can I use basically anything that can be soldered and conduct electricity?

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  • The grounds just need to all eventually connect to ground… somewhere. Your diagram is incomplete. See this from the same site - sixstringsupplies.co.uk/products/sg-wiring-kit - which is very similar, but shows the full path of all the connections. Some just go to the general ground plane.
    – Tetsujin
    Commented Feb 14, 2023 at 11:05

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@1.) The grounding of a volume pot casing should not lead to no sound from the pickup, just to a risk of noise from static on the pot casings. Now, if you ground the ground lug of the volume pot over the casing as done in this image and the casing is not grounded itself the pot will stop working and basically act as a bit of extra resistance on the path (so the pot would always be full volume but add load).

If the pickup is grounded by the pot casing as done in this image this will mean that the pickup is not grounded, which will prevent the pickup from working.

So depending on how the wiring of your guitar actually goes this might very well be the case.

Of course you could simply try it out: Ground the pot casing by pushing a wire onto it and any grounded part and check if it solves the issue.

@2.) Try to use insulated wire, else you do need nothing fancy there.

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  • The pickup is grounded to the pot casing, so that's what I was hoping to hear. I'll try it out in the next few days and see what happens. It was basically what I already planned, but I thought I'd ask here for some security that I wasn't about to set anything on fire.
    – Chris H
    Commented Feb 14, 2023 at 11:18
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    @ChrisH You are talking about low power electric signal. Nothing involved in the guitar will be able to set anything on fire or electrocute you or anything. Also it should not be possible to fry anything in the guitar from overvoltage (which would be a case if ICs were involved). Also trying out is quite simple and fast. If you do not have any spare wire than anything that conducts electricity does the job.
    – Lazy
    Commented Feb 14, 2023 at 11:29

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