Ground problem...........

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by Blueswede, Feb 12, 2005.


  1. Blueswede

    Blueswede Gold Supporting Member

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    Okay, here's the problem. I just did my first attempt at replacing a pickup in my LP reissue. Everything seems to work fine, except that I now have a buzz that was not there before I swapped out the pup. I have the ground wire from the pup soldered to the volume pot, as the directions stated. What might be the cause of this new noise? It goes away as soon as I touch anything metallic on the guitar, so I assume that it's a ground problem. Any suggestions? Thanks. Steve
     
  2. BPlexico

    BPlexico Member

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    Steve - You wouldn't happen to have a multimeter would you? You can use it to measure/verify continuity in your wiring connections, and ensure that all your grounds are properly connected.

    Does the volume pot have a ground that leads to the main ground wire, the one that is connected to your bridge?

    There are a number of ways to wire a Les Paul - not sure which wring schema you used, but here is one example of wiring from the Seymour Duncan site:

    http://www.seymourduncan.com/website/support/schematics/2hum_2vol_tone-w-3way.html

    And a collection of wiring diagrams from the Les Paul Forum:

    http://www.lespaulforum.com/forum/showthread.php?t=88796&highlight=wiring+diagram

    What pickup did you have in there and what did you replace it with? Bridge or neck?

    -- Barr
     
  3. BPlexico

    BPlexico Member

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    Also if you merely replaced one pickup you probably had to de soldier and the re soldier the following:

    a. wire running to the toggle switch

    b. ground wiring to toggle switch which is attached to base of the volume pot (usually braided shield)

    c. lead wire running to pickup

    d. ground wire running to pickup which is attached to base of volume pot (usually braided shield))

    e. And depending on pickup the ground to the bridge (also soldiered to base of pot)

    Does this sound about right?
     
  4. Blueswede

    Blueswede Gold Supporting Member

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    Barr- first, thanks for taking the time to reply not only once, but twice.
    I replaced a WCR Fillmore with a WCR Darkburst as the Fillmore was just too bright. I desoldered the FM at two points, where the red was soldered to the volume pot, and where the ground wires were soldered to the back of the volume pot. And then I soldered the DB back onto the same points. One thing I did notice was that the FM ground was soldered at the same point where the tone pot was grounded to the volume pot. I did not use the same point to ground the DB, as it just seemed easier to use a different spot. I do have a multimeter; how would I use it to check the grounds? I am going to order an R7 upgrade kit from RS and replace all of the pots and caps in the near future, but it would be nice to get rid of this darn buzz. Thanks for all the good advice. Steve
     
  5. Mark Robinson

    Mark Robinson Member

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    Your last post leads me to suspect that you may have created a ground loop, by grounding the pickup in a second location. I'll try to explain. There is one path to ground from the jack to the control network. Then each component, pot, switch or pickup, should have a single connection to that ground point. Sometimes there's a plate under the four pots in the newer Gibsons. This plate makes the ground from pot to pot. You don't need another wire. But that may not be what you have. What could be happening is that the sheilds run adjacently in the guitar body. As long as they all ground at one point, it's ok. But if you moved one, you could have inadvertently created a loop of wire in the guitar which acts as an antenae for field hum. I'm fighting with just such a situation right now, it's not real easy. But it would be worth it, to ground it the way it was, to see if it improves. Sorry for the convoluted post... Good luck.
     
  6. BPlexico

    BPlexico Member

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    Steve -

    With the multimeter - if you have a continuity setting (better still if it is both an audible and visual one) - you can attach one lead to each side of a ground connection to ensure that everything is connected properly.

    For example since all pots (volume and tone) should be grounded, touch the back of pot #1 with one lead and the back of pot #2 with the other, you should get a beep from your meter. You can than proceed to repeat, pot #1 to pot #3, etc..

    You certainly should check first that there is continuity between the volume and tone pot for the Darkburst since this is the are you were soldering in.

    Also do you have a ground wire which appears to go to the bridge?

    You would also want to put the lead on that and then try the back of each pot as well to ensure you have a connection (proper ground).

    One other thing you can try is to see if the tone and volume controls connected to the Darkburst are working properly, I assume they are?

    What Les Paul model do you have - as Mark R mentioned - different models may be wired and grounded differently (I didn't know that some had a ground plate - mine don't)?


    Anyway - best of luck - let us know how you fair - I have had a number of wiring miscues myself, very frustrating.

    -- Barr
     
  7. Blueswede

    Blueswede Gold Supporting Member

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    Barr- I have a 1997 Historic reissue. I don't see any ground wire going to the bridge. Is that typically what is done? I'll try checking all the grounds with my multimeter. BTW, the pup I replaced is the bridge one. Thanks again for all the good suggestions. Steve
     
  8. BPlexico

    BPlexico Member

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    The ground wire going to the bridge on my 2003 Historic is a thin piece of unshielded metal wire, that comes out of the side of the control cavity, near the neck volume control. It is attached to the neck volume control.

    -- Barr
     
  9. Blueswede

    Blueswede Gold Supporting Member

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    Just wanted you all to know that I went back and resoldered the ground wire back to where it originally was, and lo and behold- no more buzz!! Thanks for all of the great advice. You guys are the best. Steve
     
  10. alderbody

    alderbody Member

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    as soon as i read your post i was sure it was a "cold solder" issue.

    glad you found out by yourself.

    (had to reply though) :)
     
  11. Blueswede

    Blueswede Gold Supporting Member

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    Okay, so what exactly is a "cold solder' problem? Just so I know for future possibilities..............
     
  12. BPlexico

    BPlexico Member

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    Cold Solder Joint, also called a cold joint.

    Solder joint where the solder hasn't fused to the base metal due to the fact that the base metal was not hot enough or dirty.

    Or

    Solder joint is not smooth and shiny - this could be a cold solder joint. The causes could be a dirty tip, not enough heat or joint moved during solidification


    In reference,

    http://www.teamnovak.com/How_to/How_To_Solder/solder.htm


    Peace.

    -- Barr
     
  13. Blueswede

    Blueswede Gold Supporting Member

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    Ah,.....now I see clearly! Thanks for all the help. Steve
     
  14. fig

    fig Member

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    Since we're talking about grounding problems: I have a Cort M800 (semi-hollowbody). I didn't have a problem with grounding with the original pickups (although they were bad) or with some Seymour Duncan's I put there (but I didn't like them, so I'm trying to find something to replace them).

    I tried some WCR's, but there was a grounding problem that my guitar tech could not fix (actually, I tried a Fillmore in the bridge along with the SD '59 in the neck, and there was a pop when switching between pickups). So I decided to put some DiMarzio Classic PAF's in there. These are double waxed, but the grounding problem is back.

    With the DiMarzios, there's just a buzz when I take my hands off the strings.

    Like I said, this is a semi-hollowbody, and the guitar tech said he can't get in there and ground it like a solid body, so does anyone have any suggestions?
    thanks -
     
  15. BPlexico

    BPlexico Member

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    Usually a hollowbody will have a ground wire running to the bridge or tailpiece - just like a solidbody.

    Given that everything used to be fine in your guitar, it sounds like one of two things are possible, either that one of the ground connections is not soldered in properlu, or that perhaps the ground wire to the bridge/tailpiece has become disconnected.

    I really don't think the grounding problem is caused by the pickups themselves.

    Suggestions include emailing Cort to see if they have a wiring schematic they could send you, including the ground connections, or alternately, and I mean this in the nicest possible way, try another tech...

    Or you could take the time to pull the pots once again and verify that all your electrical connections are sound, and try and look inside the guitar (if you have one of those small mirrors on a handle that let you look inside, they have them at most hardware stores) and see if there is a detached ground wire...

    -- Barr
     
  16. fig

    fig Member

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    Thanks, Barr. I will check it all out.
     
  17. BPlexico

    BPlexico Member

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    Best of luck - I know from personal experience what a pain in the *** it is to pull the pots and pickups from a HB....especially if you need to do it multiple times....

    -- Barr
     
  18. fig

    fig Member

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    That's why I'm having the guitar tech do it. :D
     
  19. BPlexico

    BPlexico Member

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    Smart move, life is too short....better to play guitar, and let someone else deal with the bowels....I have spent way too much time taking apart and dissecting guitars...guess I should heed my own advice eh?

    -- Barr
     
  20. Andy J.

    Andy J. Member

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    I'm hijacking an old thread here, sorry guys!

    It seems that the previous owner of my '96 LP Std has been smart enough:BITCH to rip out the ground wire that's supposed to go to the bridge from the control cavity... Any tips on replacing it? I know it's usually an unshielded solid wire as opposed to a braided one, but is it possible to replace it without trying to pry out the bridge posts??
     

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