Grounding issues post pup installation

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by Gasp100, Jan 3, 2008.

  1. Gasp100

    Gasp100 Silver Supporting Member

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    Well, I installed my GFS pups today in my partscaster. I'm a total soldering noob and it was much easier to DE-solder than to get the new pups soldered back in, but I was surprised after I was finished that they all worked and the switch was working too. All of the electronics are original (~14 years old at this point) and I probably need a new switch (and new pots) but I'm not skilled enough to swap out the pots yet.
    Anyway, I think the pots are 500 vs. 250 because they have 500 stamped on the back? And they are VERY bright. Maybe I should consider switching to 250 for this strat?
    Now that the guitar is back together I have some issues.
    I'm getting a really bad buzz when I'm not holding down the strings on the guitar. This is way beyond pup buzz, it seems to be ground related because if I put my finger on the bridge or my hand across the tuning machines it stops immediately. Oddly enough I have this same issue with another guitar which I have not modded so I figure if I can fix this one I might be able to fix the other guitar as well.
    So, what did I screw up??? All ground wires (3 pups and bridge and output jack) were soldered to the back of the volume jack... it was a messy ordeal as well and I wasn't sure if any of the actual ground wires should touch one another. Getting them to stick to the back of the volume pot was next to impossible, so I'd hate to have to undo it and try again.
    I tried the mod moving the middle tone control to the bridge and it worked, but I'm getting some serious crackling when I use it. Also, if I open up the tone control above about 3 it crackles and then jumps from bassy to really trebley... basically there's no in-between tones... bummer.
    Finally, the B and high E strings have this really pinched sound. I guess it could be the neck, the nut pinching the strings, I'm not sure.
    Might be time to take it to a pro - :worried unless you have some quick things to check under the hood.
    Thanks! The GFS pups sounds spanky and sparkling besides all the noise
    :dude
     
  2. Gasp100

    Gasp100 Silver Supporting Member

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    With the strings (and neck off) I removed the shim I had placed in there and I also opened up the cavity to clean up the wiring and see what was doing. The soldering connection of the bridge pup to the swith broke loose forcing me to resolder that and another connection to the switch. I reconnected everything, put it back together, strung up with 10's and the electronics (in particular the tone control on the bridge are sounding much better). I worked on the neck to remove most of the fret buzz using the built in shim, but I need to get the right tool to adjust the truss rod a bit.
    I played through 6 different guitars last night in my amp and my DAW and the ALL have varying degree's of that ground loop sound. The only one that is almost completely quiet without a noisegate on using the DAW is the humbucker guitar... so, is there something I might be able to do to the outlets where I run this stuff? (I might repost this in the main guitar forum as well).
     
  3. Mark Robinson

    Mark Robinson Member

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    Don't want you to feel ignored buddy! What you are working on is sort of difficult to diagnose without the guitar in hand. What I would offer is that if you have shielding, you need to be even more careful with your grounding scheme. I am not a pro but here are some things I've observed in many years of wiring my own guitars.

    You want one path to ground for each component in the instrument. The guitar jack ring is the final point. There are several ways to execute a good "star" or "series" grounding scheme. The thing that will guarantee hum is when you have multiple ground paths. What I'm trying to say is if you have a shield that is in contact with something, it serves as a path to ground. So when you have a wire also going to ground, presto, that's a loop antenna and you have hum. So if your pots all live in a shielded space and are in contact witha grounded shield, you may not need additional ground wires connecting the pots to ground.

    In your shoes, I would look at the diagrams on Seymour Duncan's website, follow them carefully. If you are shielding, make a single connection to ground for the shielding material, and insulate the shield from other ground paths. The things being "shielded" need to be in proximity, nominally surrounded by the shield, but not electrically bonded to it. The shield needs a single connection to ground.

    In my experience, even humbucker equipped guitars, get a little hum, when you compare open volume, no hands on strings to, open volume, hands on strings. The only guitars I've seen that don't hum a little with high gain amps are guitars with EMG setups. Best of luck to you. Lots of good information is available if you google guitar wiring.
     
  4. has-sound

    has-sound Member

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    Since touching the strings quietens the hum, the first thing that I would check is your string ground (the wire going from the back of your volume pot to the bottom side of the bridge). Make sure that it is making solid contact at both connections.
     
  5. justonwo

    justonwo Member

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    If the hum goes away when you touch the strings, that already tells you the strings are grounded. If they weren't, touching them would have no effect on the circuit whatsoever.
     
  6. has-sound

    has-sound Member

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    doh...my bad. I was actually thinking that when I posted. Dont know what happened between my brain and my fingers. What I meant was to check the ground wire on your output jack.
     
  7. Jiffy_Jeff

    Jiffy_Jeff Playin Tunes and Having Fun! Silver Supporting Member

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    +1 on the Shielding....

    Also, you might be able to run a ground, or and extra(you'll have to flatten out the strands of wire) up under the PG to the bridge.
    That is if there is not one there.. Run it under the bridge and, put the bridge back on.

    You can also test it by holding on to your strings, then grabbing a live microphone. That should let you know if something is not right.:worried
    Actually, I'm kidding, do not grab a mic if you think there is a grounding problem anywhere in the mix......... It hurts.......

    I speak from personal experience.... Got up to sit in with a buddy of mine, picked up his second guitar, held the strings, put my lips to a mic, got 120 volts, and yelled the F word so loud China could hear it:BITCH!!!!

    Newbie sound guy!!! Inexperienced band, and stupid me... Usually when I sit in off the cuff, I grab the strings, then do a quick slap on the mic to see if I;m gonna get a jolt. If it pisses off the sound guy, so what..... Your lips will thank you....
     
  8. jefesq

    jefesq Gold Supporting Member

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  9. walterw

    walterw Gold Supporting Member

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    a little of this effect is normal unless you use emg's. you can reduce it with heavy shielding, but more to the point, proper playing technique renders this whole issue moot. you shouldn't have the guitar volume up without your hands on the strings anyway, either playing or muting them.
     
  10. LVC

    LVC Senior Member

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    The other thing you might want to check before you make yourself nuts (like I did) is your guitar cable.

    I had new pickups put in my Les Paul and it started to hum. High end pickups (wolfetones) High end guitar -- 59R LP C9 ---- I took it to several guys to check it out -- nothing -- plug it in -- noise. I would put my fingers on the strings etc -- hum disappeared.

    ---- I love this guitar it is one of my prized possessions ---- I was ordering new speaker cables from Pro Cables and Sound

    http://procablesnsound.com/

    and decided what the heck let me order couple of guitar cables while i am at it.

    I am glad I did. Noise gone --- zero -- nada --- zilch. Quiet as a mouse.

    For whatever reason guitar was more sensitive after the pickup change and the George L's I had been using (for years) was introducing noise.

    Sometimes it is the simplest of things.
     

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