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Wiring questions/help. Long post

Discussion in 'Pickups & Electronics [BG]' started by fordkisskrazy, Jul 20, 2012.


  1. Hey all I have some questions hoping to get some answers/help with.
    I have a epi tbird pro IV. Active bass, I am changing it to passive. It has 4 knobs so I was going to do v/v/t and a 3 way switch,b/bn/n. Here is the diagram I used. tbirdwiringwithtoggleswitch.
    Now when I did this everything worked except that both the volumes affected each other, the neck volume worked fine but the bridge volume was either full on or nothing and when I turned it to 0 it shut everything off. Also it hummed loud as heck. Am I missing something?
    I wired it like a jazz bass, here is the diagram. tbirdwirediagram.
    It works perfect like this, no hum or buzz. volumes work right,tone works. Pickups loud and clear. I don't want a dummy knob that's why I was doing the 3 way. Plus I do use only 1 pickup sometimes. What am I doing wrong?
    Oh ya the pickups wire are one wire out with 1 red 1 white wire rapped in bare wire inside of it. I ran the white as hot and the bare as ground. The red wire just seems to cause the hum or buzz when used. I tryed the red and white as hot and ground and the white works right as hot, red just causes hum and buzz.I have no clue what the red is for...maybe for the battery when wired as active? They weren't separated when wired active just soldered to the blend pot. Any suggestions?
    Sorry such a long post just trying to give ya all the info.
     
  2. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    See the way the volume pots are wired up in your first circuit? That's why they are interacting.

    Just swap the terminals where the pickups connect with the terminals gong to the switch, as it is in the bottom schematic.
     
  3. You used one of my diagrams. That wiring is meant to allow the wiper terminal to function as an output, providing a more-or-less constant input impedance against the pickup coils. The problem, however, is that this means the volume pots vary output impedance, so rolling one down will kill the output for both pickups if the pickup selector has them both on. The alternative is to swap the terminals around on the volume pots, so that the wiper terminals will vary input impedance against the coils. This will allow independent control when both pickups are selected, however, the drawback is that there is a variable-impedance loading effect on the pickups as the volumes are adjusted. Apparently both ways of wiring have their fans.

    I'm a bit confused by what you said about the loud humming when the volume is rolled down. If you had wired properly, the output impedance would be reduced to zero when the volumes were all the way down. This means that the only flow of electrons to whatever the bass is plugged into will be what can be induced in the cable throughout it's equivalent series resistance. This is essentially dead silence. Are your volume pots grounded properly?
     
  4. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Make sure you also ground the backs of all the pots together too.
     
  5. Thanks all! Will try swapping the wires like stated by you both. I ment to say with the volume up I am getting the hum/buzz not turning it down, and yes the pots are grounded. Thanks again, will let you all know how it ends up. Oh! should I change where the cap and hot out put to jack are? No, wait, they are the same in both diagrams so I should be good right?
     
  6. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    The tone control is fine.
     
  7. IT'S ALIVE! IT'S ALIVE!! Thank you guys for your help! I wired it like you said and everything works great. :hyper: She sounds awesome now. :bassist:
     
  8. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    :bassist: :D
     

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