Correct Control Wire for Les Paul?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by jkats, Dec 27, 2009.

  1. jkats

    jkats Member

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    Location:
    Portland, ME
    I've been working on what should be a simple pickup switch in a 90s Les Paul Classic. I installed new CTS pots and Jensen PIO caps in a RS prewired harness and Duncan Ants. When I hold the guitar up without touching the strings, there is a light hum (I know, maybe it doesn't know the words ... ). The tailpiece ground is soldered on, the terminals are wired correctly, there are no cold solder joints and the output jack is fine. However it looks like there's been a history of ground issues with the guitar, since a previous owner installed copper shielding foil in the pickup cavities and on the inside of the control and switch covers, and even soldered wires from the back of a pot to the cover and (this is the fun one!) from the switch output -- not the ground -- to the switch cover. I've fixed the obvious problems, but think the two remaining possible issues are the switch itself and the four-stranded cable from the switch to the control cavity. I know where to find a switch, but where do I find the cable/wire? Thanks in advance for your help!
     
  2. walterw

    walterw Gold Supporting Member

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    a slight hum when not touching any metal is normal. heavily shielding everything can somewhat reduce it.

    there's no reason to replace the switch and that cabling run, assuming the run has a grounded jacket shield like they normally do. they either work or they don't.
     
  3. Bob V

    Bob V Member

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    Does the hum go away when you touch the strings? the toggle switch ring? pickup covers? jack? or does it get worse? I'm a believer in shielding; paint is my current preference because it's cleaner in the end (after you clean up the mess) and it can't ever come loose. But shielding can create some problems - if you connect the hot side of the circuit to it it will either short everything else or it will hum like crazy.

    If the prior owner messed up by connecting the hot wire to the shielding, then maybe the same mistake was made with the shielded multiconductor cable from the switch to the control cavity. There's a bare wire that usually has a piece of loose yellow insulation sleeving on it in the control cavity, and that is where the shielding on the cable gets its ground. Technically you don't need the signal ground to run through that cable, just the shielding. At the other end, you can connect the bare wire to the ground/shield terminal on the switch which is not part of the switch circuit but it will ground the body of the switch and that should be touching the foil in the switch cavity.
     

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