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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Not your normal wiring hum question...

Discussion in 'Tele-Technical' started by Huddy, Sep 3, 2017.

  1. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    I just wired up a Jag-Stang that I scored off craigslist that was in need of some loving. I replaced the switches, pots, and jack. All is right with the world... except for when I touch the humbucker mounting screws. The all hell breaks loose - especially on a gain channel.

    I'm thinking that the mounting bracket has somehow come un-grounded and when I touch the screw the antenna that my body is connected to the screw and all the frequencies are sent to the pickup. This sounds right, right?

    If so is an easy none invasive solution to just solder a wire from the bracket to the back of a pot? Or would that not work?

    Thanks!
     

  2. sjruvolo

    sjruvolo Tele-Meister

    427
    May 22, 2013
    New York
    Either you have reversed the ground and positive wires on the pickup or the jack. This just happened to me recently when I rewired my American Special Strat. I reversed the +/- wires on my out put jack and when I touched metal the guitar hummed like mad. The opposite that usually happens with a properly grounded guitar.
     

  3. philosofriend

    philosofriend Tele-Meister

    471
    Oct 28, 2015
    Kalamazoo
    If the output wires are reversed like sjruvolo said, and the strings are grounded, it will hum when you touch the strings or any metal on the guitar.

    If the strings are grounded and touching them makes any hum quieter, and touching the pickup mounting screw causes hum, then you are correct that you need to run a ground wire from the back of a pot (or any other ground) to the metal frame of the pickup (or a mounting screw).
     

  4. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    Here's the update. The jack is all good. No hum regardless of whether or not I'm touching the strings, jack, bridge, stop bar, control plate, whatever. The only time that it hummed was when I touched the bridge humbucker mounting screws.

    Everything worked perfectly with the in/out phase on/off/on individual pickup switches.

    In my mind this meant that the mounting bracket itself was not grounded. I tested it with a multi meter for continuity. No nice.

    I scraped some of the wax off and soldered a bit of wire from the back of the pickup bracket to the ground output of the bridge switch as this goes directly to back of the volume pot which goes to the ground lug of the jack.

    I wasn't really thinking when I did this after I buttoned it up realized that I must've created a short when I had no sound when the bridge switch was slid closest to the bridge setting. I don't know how that's possible because if the bracket was never in the circuit the result should be a lot of hum when the selector is there as it's directly in the circuit.

    So then I took it apart again and removed the jumper from the back of the pickup to the switch just to be safe and put it to the ground lug in the pickup cavity and which goes directly to the back of the pot.

    Same as the first jumper on the back of the pickup.

    It's possible I have an intermittent problem with the bridge pickup OR somehow there's an unwanted connection on the bridge pickup switch - like I didn't snip excess wire and it's touching something it shouldn't. I feel like I'm getting some sort of series/parallel think going in addition to the the out of phase which less redundant that the factory setup but not what I want. Especially since I don't really know how to control it at this point.

    I'll add some pics when I get some time this evening but any comments or advice would be greatly appreciated. I have two more switches so I can start from scratch if need be.
     

  5. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    If you have the hot and ground wires on the humbucker backwards, then touching what's supposed to be a grounded part of the pickup will make a bad noise like when you touch the tip of the guitar cord - is that what it sounds like? Also with a backwards connection, adding another wire from the pickup baseplate to actual circuit ground will short out the pickup.

    There's probably an internal jumper from the grounds side of the pickup leads already running to the mounting plate on the humbucker, which would mean if there was a metal cover on the pickup it would be shielded; otherwise touching the screw should not be very dramatic.
     

  6. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    The noise was very similar to the interference you get if you've got a lot of electronics plugged up right near your rig or dimmer switches. But it was only when you touched the screws. So I knew that the bracket was not grounded. The humbucker pickup lead is a thin inner pvc insulated wire with the stranded ground shield wire surrounding that with the pvc final outer cover. So not easy to mix up but I've done dumber things in my life.
     

  7. dsutton24

    dsutton24 Poster Extraordinaire Ad Free Member

    Dec 29, 2010
    Illinois
    You know, I've got a guitar that did this too, and I have no idea why. I ran a separate ground wire to the two pickup mounting screws. I connected the ground wire to the screw by installing a ring terminal on the wire and trapping it between the spring and the pickup ear. Weird, but it worked.

    There was an old broadcast engineer that I used to work with who was really fond of the old saying, "Ground ain't ground the world around." He had a point.
     

  8. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    That's a nice smart and minimally invasive solution... That I wish I had thought of... :-|
     

  9. philosofriend

    philosofriend Tele-Meister

    471
    Oct 28, 2015
    Kalamazoo
    It sounds like you have the two wires from the pickup reversed. That would explain why the sound stopped when you put the ground jumper to the pickup frame. It also explains why you would get hum when touching the mounting screws.
     

  10. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    There was no continuity between the stranded outer shield of the pickup lead and the mounting bracket/screws.

    The bridge pickup works fine in bridge pickup selector positions 3 and 2. It cuts out all sound in position 1.

    Keep in mind this is a jagstang with two independent on/off/on switches wired with phase reverse.
     

  11. philosofriend

    philosofriend Tele-Meister

    471
    Oct 28, 2015
    Kalamazoo
    No sound in position 1 when you tried the jumper wire, right? Without the jumper everything still works but there is the original hum problem.
    Is position 1 the opposite phase option for that pickup?
    Does the outer shield of the pickup lead have continuity with either of the other leads?
    Does the pickup frame have continuity with either of the two regular pickup wires?
    Can you take a cover off the pickup and see what the wires are doing in there?
    To be used in phase reversing the pickup needs its frame connected to the shield or ground wire only. The two main leads need to be grounded only through the selector switch, one at a time on alternate phase choices. Once you have proven that to be true you are ready to get the magnifying glass and look for a short around the switch. The switch could be bad inside but that is less likely.
     

  12. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    This is what's confusing to me about phase reverse on this guitar with the humbucker. You should have a hot, a negative, and an earth ground, right?

    I put it down for a day to come back to it with a fresh mind. Gonna work on it this afternoon.

    I replaced the switches with new switchcraft switches cause the original we're nasty, crusty, and sticking.

    So let's establish the positions so we're talking about the same thing.

    Guitar sitting on your lap, face up.

    #3 - All the way left - normal
    #2 - Middle - Off
    #1 - All the way right - phase reverse

    I'll attach some pics when I get home in a bit.

    Thanks for the help!
     

  13. Huddy

    Huddy Tele-Meister

    Age:
    34
    211
    Nov 5, 2016
    Newport News, VA
    So I figured it out. If I would've done some more testing from the get go I would have realized it is a design flaw or the pickup has been replaced at some point. These pickups should have an earth ground.

    When I was testing for continuity I did not note the location of the selector switch. I can only assume that it was in position #1 for phase reverse since when I tested for continuity. I was always testing against the control plate instead of the ground of the pickup. There is only noise from the pickup screws/bracket in #1 Phase Reverse which makes complete sense. The pickup should have Hot (+), Signal Ground (-), and Earth Ground for the bracket and screws. Since it does not when the current (?) is flipped those items (screws, bracket, etc) be come antennas. When you connect those little antennas to the big antenna that is my body... voila... noise!

    Does this sound right? It's the only thing that makes sense. In looking at the jag-stang diagram from fender they do not designate an earth ground.
     

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