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Les Paul Wiring Woes

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by jamison162, Aug 12, 2006.

  1. jamison162

    jamison162 Member

    Messages:
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    Location:
    FL
    I just finished a re-wire of an Epi Std. and have major problems. Installed a new switch, jack, CTS pots, and Jensen caps (.022/.015). I'm using a small diameter resin core silver solder, tinned everything properly before making connections. Took my time, did it per the book. Straight-up 50's wiring. Checked out everything (continuity) with the meter.

    Here's my problems:

    1) The switch connections check out perfect, however in any of the 3 positions I'm getting weak output from both pickups; no matter what position the switch is in. Checking the switch lug on each vol. pot and the connections check out. I am baffled!

    2) The tone pots don't seem to be working at all.

    3) CTS pots, I'm pretty sure I got audio taper and not linear pots, but I am noticing the volume really jumps up the last 1/4 turn. Is this normal, I have never noticed this before.

    I following the wiring diagrams to the "T", and also have Dan's video on "How to wire a Gibson Les Paul". I don't understand how everything got so screwed up. Is it possible I fried some things. I mean, I tinned all connections and got in and out quick.

    Any advice besides tearing it all out and starting over?
     
  2. jamison162

    jamison162 Member

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    Ok, I figure it's gotta be the pots. How do you screw up the pots? Too much heat to the back of em do any damage? How do you test for bad pots?
    With both vol pots off, my pickups measure out correct; about 7.5, 8.5. When the volume pots full on, I can't get this reading anywhere. Where is my signal going? Any ideas on what to check next.

    I am still totally baffled at how I'm getting both pickup signals out of my amp (allbeit weak) when I can't get any continuity other than the way they are supposed to check out. I do not know how to proceed.

    (Oh, to explain from other postings, I'm getting BOTH pickups hot no matter how the switch is set, but very weak signals. I've checked continuity between vol pots and switch, switch and jack, and even volume pots and jacks, in all three switch positions and it checks out as it should. I'm really at a loss here.....)

    I'm no good at pics.
     
  3. jamison162

    jamison162 Member

    Messages:
    7,778
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    I only get the correct pickup reading with the vol pots totally off.
    With everything on, my reading at the jack in all 3 switch positions is 0.25-0.30 kOhms.

    Pots? Were they bad to begin with or did I burn them up - and how would one do so. The most heat I used on the project was soldering the grounds to the back of the pot. All other connections were hit quick with a 40wt iron which is what Dan uses and recommends.
     
  4. Giraffecaster

    Giraffecaster Member

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    you sure it's the pots? i'd disconnect the pots from the circuit and connect the output of the 3 way to the jack just to test.

    you might have also wired to the lugs backwards, because muffled low volume usually means tone on 0 and vol on or near 0?
     
  5. jamison162

    jamison162 Member

    Messages:
    7,778
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    Here's some pics, I'm not that good a photographer. As mentioned before, I took my time wiring up this guitar and did a good job with all the connections. They were all clean and done fast using a hot iron and silver solder, everything was tinned before connections made.

    Some of thie pics look bad and it's hard to see the connections but I have checked and double checked eveything. All soldring went fine until it came to grounding the back of the pots. It was the hardest part which surprised me - as you can see.

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  6. Jack Briggs

    Jack Briggs Member

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    You might have a short from the shielding paint to the volume pots. Slip a piece of electrician's tape under the tabs where they're riveted to the phenolic, to insulate from the shielding paint. The other thing is you want to run a piece of solid core ground wire from one pot to the next all around so your ground connection is common and solid. I always put a little piece of heat-shrink tubing on each of the connections at the switch, too. Now try the meter test.
     
  7. jamison162

    jamison162 Member

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    Ya know, I bought this guitar used so I didn't know if that shielding paint was factory or aftermarket. I didn't even know that is was shielding paint or metallic until I "happen" to touch it with a meter. It's werid stuff, I would prefer not to have it at all. I think it does cause a lot of problems.

    So how would I be getting shorted pots from it? The pots that were in there before weren't shorted. That's good to know that I may have a lead here anyways.

    As for the grounding wires, what do you mean by solid core? I did have a ground ran from the tone pots to their respective vol pots, but clipped it earlier when troubleshooting. The volume pots share a common ground via switch/braided shielding to the output jack. I just need to ground the tone pots.

    I need to put some heat shrink on those cap leads as well. if my tone contols do not respond is it possible I burned out those caps? I meant to use heat sinks but didn't as it was tight already. I didn't stay on them but a couple of seconds.

    Anyone use pots other than CTS, I wasn't craxy about the feel of these, they all measure under 500k except for one I think.

    I've heard pretty good things about Alpha pots, is that what Stew Mac sells?
     
  8. jamison162

    jamison162 Member

    Messages:
    7,778
    Joined:
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    Location:
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    I went ahead an disconnected all leads in the cavity and pulled the caps out.
    So far this is what I have found:

    1) Pickups are good testing at 8.65k, 7.75k.

    2) Switch is good getting the same reading on each isolated pickup and the proper value running both. (Resistance in parrallel is the inverse of the sum of the recipricals; really impressed the wife calculating this one and having the meter read exactly what was calculated, wow!! +1000).

    3) Same results at the jack as the switch. Plugged in everything sounded fine and wide open.

    4) Vol. Pots: Checked these out by clipping the leads to the center and outer lugs that the pickups and switch legs were connected to. Measurements went from 500k +/- (off position) to 0k at full volume (0 resistance). Both neck and bridge pots checkd out if this is right.

    That's where I'm at. If all of this sounds right to you guys, I'm going to pick up a desoldering bulb (desoldering braid doesn't work to good for me), do some cleanup and proceed from here.

    Thanks for all the help!
     

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