Wiring help - 2 hums, V-V-T w/ Coil Split

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by KaBudokan, Nov 10, 2005.

  1. KaBudokan

    KaBudokan Supporting Member

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    I'm trying to work out the wiring for my current project while I wait for the finish to cure a little longer. The guitar will has 2 WCR humbuckers, and the control setup will be 2 volumes, 1 tone, a 3 way gibby switch, and a push-pull on the tone control to coil tap both pickups. I am setting the coil-tap to activate the outside coils of the humbuckers.

    I did a mockup of the wiring today to test out what I thought was going to work. I basically just set up the controls (sticking them in cardboard to simulate the control cavity), and wrapped the wires at their corresponding contact points. I hooked up the pickups and the jack this way, and by touching the pickup slugs with a screwdriver I could check what was working.

    I was able to get the normal setup working fine, but the coil tap did not seem to work at all.

    First question: If I am coil-tapping a humbucker, does that mean that if I touch the slugs of the "inactive" coil I shouldn't hear anything? This is what I figured, but if I am wrong, then the rest of this is a non-issue, as the coil-tap could have been working fine. :p

    I couldn't find quite the right diagram for my exact wiring setup, so I combined two that seemed like they would work:

    This one from SD gives the basic layout -

    http://www.seymourduncan.com/support/schematics/2hum_2vol_tone_3way-w-spl.html

    Then I used the diagram for "Humbuckers (2)/Outer Single Coils" for the tapping -

    http://www.guitarelectronics.com/category/wiringresources.1wiringdiagrams.humbuckerwiringmods


    Assuming I was right about not hearing anything when touching the inactive coil when it is tapped, I couldn't get the coil tap to work at all. Even doing the basic one pickup coil tap from the SD diagram didn't work.

    Any thoughts?
    :confused:
     
  2. Jim Collins

    Jim Collins Member

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    Which are the two wires of the WCR that are joined together? What -- and I mean exactly -- did you do with these joins?

    The join of one pickup should go to the bottom, left lug of the DPDT switch that sits on the back of the tone pot. ("Bottom" means one of the two lugs that is closest to the tone pot casing.) The join of the other pickup should go to the other bottom lug of that DPDT. Then, connect a new lead that jumpers across both middle lugs, and goes to ground (volume pot casing). When the tone control is pushed in, the joins don't go anywhere. When the tone control is pulle out, the joins are sent to ground, which shorts out the slug coil of each pickup (assuming the other leads are connected correctly), leaving only the adjustable pole piece coils available to the circuit.

    Here is the diagram that shows two volumes, one tone, and a three-way: http://www.seymourduncan.com/support/schematics/2hum_2vol_tone-w-3way.html

    Notice the two red+white joins. These are the things that should go to lugs 3 and 6 (bottom) of the DPDT. (Of course, WCR colors might be different.) Then, connect the new lead that I mentioned.
     
  3. KaBudokan

    KaBudokan Supporting Member

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    Thanks for the help, Jim. Here's a question:

    Does hooking the red + white leads to the bottom lugs of the DPDT (as you described) have the same effect as hooking them to the middle lugs, and then sending the bottom lugs to ground?

    Almost all of the diagrams I see say to hook the red + white to the middle lugs and ground the bottom, which is the opposite of what you described.

    I am not sure what's up with the diagram from the Guitar Electronics site - it has one of the bottom lugs grounded, and the other attached to the hot lead from the bridge pickup.


    I actually just wired it up how you described, except I put the red + white leads on the middle (as described above). This seemed to do the trick. When the switch was activated, you could definitely hear some hum coming into the signal path, and the slug bobbin lost most of its volume. (Apparently touching it with something metal will still produce sound, as they are still within the magnetic field, or something like that. This answered one of my previous questions.)
     
  4. Jim Collins

    Jim Collins Member

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    It doesn't matter whether you did it as I described or as you described. The DPDT switch is a double pole switch, which means it has two poles, or switches, built into one housing, operated by one switching mechanism. The two switches are independent. Let's number the six lugs one to six, with the three lugs on the left being 1 to 3, and the three lugs on the right being 4 to 6. Furthermore, 3 and 6 are the bottom lugs, closest to the pot, itself.

    Lugs 2 and 5 are the common lugs. When the control is pushed in, lug 2 is connected to lug 1, and lug 5 is connected to lug 4. When the control is pulled out, lug 2 is connected to lug 3, and lug 5 is connected to lug 6. So when the control is pulled out, the red+white of each pickup is sent to ground, whether you wired it as I described or as you described. I tend to use the common lugs as the output, but that is just how I do things. There is no technical reason to do it one way or the other.
     
  5. KaBudokan

    KaBudokan Supporting Member

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    Thanks a lot for the information. I'm kind of amazed about this, but now I actually understand the technical reasoning behind this wiring setup, rather than just counting on using a schematic and having no idea what it actually does.

    Cool. :D
     

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