Guitar Grounding Common Misconceptions?

Discussion in 'Tonefreaks' started by jonesy, Jul 23, 2010.

  1. southpaw219

    southpaw219 Member

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    Hi, Jonesy. Thanks for sharing your wealth of knowledge on these boards. I'm doing my best to learn how to do my own guitar work, but I'm finding certain hurdles along the way.

    I'm very wary of soldering to the back of pots. I know it's been done for a dog's age and all that, but I just don't like the idea of them absorbing all that heat. Even from just touching the casing for a few seconds with my 40W iron, they cook.

    So, I've been looking into alternative grounding methods and came across the "star" idea. I felt pretty excited about trying it out, but after reading your posts about the different kinds of ground circuits and how the bus wire is essential to link all the pots together, I'm a little crestfallen.

    Please look at the diagram below, which I made to depict how I'd ideally rewire my Swede (in its stock configuration). Could you explain to me if I'm way off course and, if so, how I can correct it?

    Thanks.

    [​IMG]
     
  2. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    Learning to solder is an essential part of modding and upgrading guitar wiring. The more you solder, the better you should get at it until you feel more comfortable soldering to the back of the pots. "Practice makes perfect" they say. ;)

    The star grounding is a modern approach to wiring and you can see it used in many of the diagrams for Bourns pots etc. but is not a wiring method that I ever use. Most, if not all of my LP rigs get wired up with the vintage 50's style wiring. With the star grounding you end up with a lot more wire inside the cavity and it can turn into a cluster, just look at your wiring diagram. Grounding to the back of the pots has worked for over 60 years, very simple effective method for guitar grounding.

    I looked at the diagram you supplied and it looks like the caps are soldered to the tone pot and then right to ground (modern wiring) vs going from the tone pot to the center lug on volume pot (50's wiring) so you will most likely get some muddiness when the volumes are rolled down. 50's wiring preserves your highs and is user friendly with tube amps.

    It's good to try new things, but don't shy away from soldering to the back of the pots and 50's style wiring in lieu of a different wiring method just because it is easier. Learn the basics, practice soldering on some old pots until you get the hang of it and you will have the skills you need to get the job done correctly. YMMV
     
  3. southpaw219

    southpaw219 Member

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    Hi, Jonesy. Thanks for the reply. You're right that I depicted the stock scheme. Here's the same "star" grounding idea, but with the '50s scheme.

    Additionally, do you have any feedback on the "tone filter" switch I've depicted? I understand what it does -- changes the capacitance value applied to the tone -- but I'm not exactly clear on how it does it and what, exactly, it does, scientifically (as opposed to aurally). Those two caps on the tone filter switch are 4700 pf and 0.015 uf.

    And, finally, when I disassembled my guitar, I found that the pot shafts were significantly corroded. The holes in the body through which they go are caked in white dust akin to (and, I infer, directly from) the corrosion on the pot shafts. The hole for the input jack is similarly caked in white dust. Is this a sign of a significant problem?

    [​IMG]
     
  4. southpaw219

    southpaw219 Member

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    Don't know how much of a foul it is to follow my own post without a reply, but I mocked up a scheme wherein I use wire with a braided shield. I'm still avoiding soldering to the backs of the pots, but I'd appreciate any feedback.

    I revised it a little to ground the lugs of the tone and volume pots to both the incoming braided wire from the pickup and the outgoing braided wire to the switch ... I've heard countless debates about grounding loops, and I don't know if I've depicted any ... but the diagram is there to be critiqued.

    Thanks.

    [​IMG]
     
  5. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    Oxidation can be caused by environmental conditions and also by the materials involved. I would just make sure that everything get's wiped down good and none of that residue is left when you install the new pots.
     
  6. southpaw219

    southpaw219 Member

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    I was actually considering keeping the original pots, since they're CTS and they have resistance pretty close to their rated 500 kOhm values:

    Neck volume: 463 kOhm
    Neck tone: 498 KOhm
    Bridge volume: 478 kOhm
    Bridge tone: 473 kOhm

    I was just worried that the oxidation on the shafts might have compromised them, in some way.

    The capacitors are junk, though. I'm looking forward to when my Russian PIO replacements arrive.
     
  7. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    I you decide to keep those CTS pots they make different types of electrical contact cleaner that you can spray down into those pots and that should remove the oxidation. Spray it down into the shafts and turn them back and forth. Otherwise they may start to sound scratchy when you turn them if that white crud get's between the wiper and carbon track.
     
  8. southpaw219

    southpaw219 Member

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    Ah-ha. The pots were definitely scratchy when turned. Now I know why.

    Is there any contact cleaner you'd recommend by name? Are they more or less all the same?

    Cheers.
     
  9. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    The pots can be scratchy from the oxidation in between the wiper and track, but they can also be scratchy because the carbon track is wearing out. So if you clean them and they are still noisy when you turn them then you will need to replace them.

    I have been using Blow Off Contact cleaner for years and it works good, it drys quickly and does not leave any oily residue. They also make a Duster that just sprays air, but that is not what you want for cleaning pots. Also never use anything like WD 40 for cleaning pots, all it will do is attract dust and dirt and make even more of a mess inside the case.
    Blow Off 11oz Regular Contact Cleaner | Edmund Scientific
     
  10. southpaw219

    southpaw219 Member

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    Is there a rudimentary circuit I could rig that allows me to send a signal to my amp to test whether the pot is scratchy once cleaned? Without soldering them back into the guitar?

    I'd like to be able to do the test before re-installing the pots in my guitar and then, potentially, having to remove them again, if it proves to be the track that is the problem.

    Thanks a million.
     
  11. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    You could wire up some alligator clips onto one of your pu leads and then another set of clips with an output jack wired to the end. That way you could test each pot out individually without the rest of the circuit to see how they work after you clean them.

    Your welcome, glad to help.
     
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  12. SGguy

    SGguy Senior Member

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    Jonesy, I got a buzz problem. If I touch anything metal on or in the guitar, ANYTHING, my annoying buzz goes away. And for some reason, my neck pup still works even though the braided shield is not soldered. and finally if I touch the stud in the humbucker the buzzing gets louder. I'm confused as H E double hockey sticks.
     
  13. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    Try soldering the braided ground on the pu lead to the back of the volume pot and see if things quiet down.
     
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  14. SGguy

    SGguy Senior Member

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    no dice, I did however notice that if I get my finger close to the wire coming from the vol pot to the switch it starts buzzing more. I have melted the cover on that one a tad so I think I'll put some electrical tape on it to aid with the shielding.
     
  15. southpaw219

    southpaw219 Member

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    Just a little info ... telling someone they're "wasting their time" to do anything sounds a little insulting, even if it's not intended to be.
     
  16. Giant

    Giant Senior Member

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    I think that posters first language may not be English. He wrote "i think i should thank you very much for you can waste lot of time to write this post .....thank you again for your sharing..
    I think its supposed to read "Thank you for taking the time to write this post. Thanks again for sharing..."

    I could be wrong, but it just seems like a language thing.
     
  17. southpaw219

    southpaw219 Member

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    Yeah, it seems pretty apparent that's an English as a Second Language posting, but I don't think that invalidates my pointer that, idiomatically, there are phrases to avoid when posting in said second language.

    I speak a few languages, and I've always been grateful when people inform me of things NOT to say, or how to say something more politely / appropriately. So, I'm just paying it forward.
     
  18. ToneQuest75

    ToneQuest75 Member

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    Is the ground wire from the tailpiece to the cavity in a Les Paul really necessary? I mean, is it important from a safety point of view? The way I see it, the guitar is safer without it - since it makes a connection between the strings and the electronics circuit via the tailpiece, so potentially the strings could become live if there were a problem. Surely the guitar is safer without it, since wood is a good insulating material anyway. Or am I missing something? :hmm:
     
  19. jonesy

    jonesy GLOBAL WIRING GURU MLP Vendor

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    99% of guitars have a ground wire from the tailpiece to the wiring harness. It does help keep things quieter. I just upgraded a 1978 LP and it did not have the ground wire. After playing on it I think it would have been better off with one in my opinion.

    If you are worried about getting shocked from your amp or pa you can add in a capacitor in series and it will block any AC current trying to get through.
     
  20. ToneQuest75

    ToneQuest75 Member

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    That's interesting, because I agree in theory it should help keep things quieter, but the funny thing is, I have excessive hum on my Orville by Gibson LP, and in trying to reduce the amount of hum, I unsoldered the ground wire and the hum was dramatically reduced (though not totally eliminated).
     

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