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EMG BTC wiring help

Discussion in 'Pickups & Electronics [BG]' started by mrufino1, May 11, 2010.


  1. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    I am trying to wire the BTC into my bass, which is a JJ Helms 5 string. It has two J pickups but I have them wired in series, so control layout is like a P-Bass. I have been trying to install into this all night and it is not working. I believe I have everything hooked up as the diagram shows, but all I am getting is one of 2 things: The bass is always on (volume is having no effect) and sound is puny, or if I remove the connection between the middle lug of the volume and the pot itself, I get a feedback noise but the volume control does function. I am assuming the diagram is correct, what could possibly be happening? For pickup layout, I should have the hot lead on the pickup connected to the battery terminal and the red wire on the BTC, and the ground lead from the other side of the pickup should be soldered to either the case of the pot or the middle lug, which is also wired to the case of the pot? Then the third lug of the pot should be connected to ground on the BTC? The BTC tone controls are having no effect on the sound when there is sound, and I know the batteries I am trying are good. I am at a dead end, I just know this isn't working, so any ideas would be helpful.
    The wiring diagram is here:
    http://www.emginc.com/search/wiring
    You may have to type in BTC, I can't seem to link directly to it. Thanks
     
  2. bobunit

    bobunit I'm here. Now what? Supporting Member

    Jul 15, 2008
    Idaho
    Any chance of pics?
     
  3. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    I don't think these are going to help much but here's a few, then I'm going to bed, it's 2am here and I need to be up at 7...

    [​IMG]

    [​IMG]

    The green wire is the ground side of the pickups, the red wire is the input wire to the BTC (it is white but I have it spliced to that red one because I don't have any white wire. Lug 2 and 3 of the volume pot are both wired to the case, as it seems to appear in EMG's diagram.

    [​IMG]

    The wires on the BTC are not all the original wires, I bought it on the board here used, but everything is going where the diagram says. So either the diagram is wrong, I am missing something, or I broke something. I did try the pickups wired in series direct to the jack and they sounded like they always did in series, so the pickups work. Any insight would be cool, I may need to wind up taking it to someone.
     
  4. bobunit

    bobunit I'm here. Now what? Supporting Member

    Jul 15, 2008
    Idaho
    What is the ohm value on the volume pot? Go to bed, it'll be there in the morning. :)
     
  5. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    250, passive pickups so it should be OK.
     
  6. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    I'm up and obsessing about it! The yellow wire is the bridge ground, should that be in this circuit anymore? Seems like it should be but it isn't on any wiring diagram.
     
  7. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    Volume knob should have the #3 lug wired to case, middle is from pickup (or switch), 1 is out to BTC. If you have 2 wired to the case, that is a big ass problem. It would do what it's doing.
     
  8. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    Okay, I did that and back to the feedback. It sounds like a theramin, if I turn the volume down the pitch changes until it's off, so the volume control works but it's all feedback. Not sure what's going on.
     
  9. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    Got it- the tip and ring lugs were reversed, so battery was going to the tip. Now I just need to redo my wiring neatly, pot is scratchy but no doubt I put it through hell...Thanks for the help!
     
  10. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    All RIGHT! Those darn tube jacks need some sort of uniformity. Maybe one day...
     
  11. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    Yes, I agree. Thanks so much for your help, hardest $30 sale you ever made!! The EMG wiring diagram clearly shows lug 2 wired to the pot, I will have to tell them. Now to spend tonight doing a neater wiring job. I may figure out the series parallel switch at some date, or find something to fill the hole so I can fit the 2nd battery.
     
  12. JackANSI

    JackANSI

    Sep 12, 2006
    PA
    [​IMG]

    The longer one is ring, the shorter tip.

    If its the old kind, the one furthest from the ground is the ring, the other is the tip.


    Unless my memory of these is backwards ;)
     
  13. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    Actually, it's an EMG specific pickup wire in the diagram. It's coaxial, so the inner part of the whole cable is the pickup hot, the outer braid is a ground, but it appears to be 1 cable and connected as such.

    I should have specified that for you. And for anyone who picks up this thread eventually in the future:

    Unless you have EMG pickups
    Wire according to the diagram EXCEPT...
    wire pickup hot to the middle lug and the ground (or grounds) to the pot case.

    Friggin EMGs!
     
  14. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    That makes sense now, I am going to email EMG and suggest that they specify that. Oh well, it was a learning opportunity for sure! And as a bonus, for about 2 minutes I had a way to make a theremin sound...(the pitch changed with the movement of the volume knob). SO now, if I need a theremin, I can wire up and emg eq backwards and get one :D
     
  15. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    what on earth?

    the middle lug of the volume pot does not get grounded, it goes to the input wire of the preamp (white wire).

    the hot leads of the pickups do not go to the battery clip of the preamp.

    if the pickups are really getting wired in series, the hot of one goes to the ground of the other (and that connection gets covered up), then the leftover hot and ground wires of the two pickups become like one pickup: hot goes to the clockwise lug of the volume pot, and ground goes to the back of a pot.

    if you're just trying to get the normal sound of two jazz pickups at the same time (i.e., parallel), then both hots go to the clockwise volume pot lug, and both grounds go to ground.

    the red wire from the preamp goes to the battery clip red wire, and the battery clip black wire goes to the ring connection of the output jack.

    the green wire from the preamp is its output, so it goes to the hot of the output jack.

    all the black wires on the BTC are just for ground, so hook at least one of them to ground. use the rest to make any ground connections that are missing (like the backs of any pots or the ground of the jack.)
     
  16. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    Yes, I think my terminology was a bit off (did you look at the time of the post?!:oops:)
    I understand the issue now- emg's diagram clearly shows a connection between lug 2 and the pot case, but it turns out it is the way the diagram is drawn and is specific to the wire EMG uses on their pickups. I am not sure exactly what it is trying to show.

    Everything is working as it should now, the other problem I had was I had the terminals reversed for tip and ring, this jack was a little deceiving.

    yes, wired in series is what I wanted, and the hot wire and ground wire of the ends are going where they should now, and hot and ground connected on the other side to make the series wiring.
    pay no attention to the colors of the wires, most of them are red or black because that's the colors I have, not necessarily noting ground or not.

    but most importantly, it all works.
     
  17. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    nope, what you're seeing is the pickup's inner hot wire going to that second lug, and the outer braided ground going to the back of the pot. that's normal jazz bass wiring for two volume pots.

    also, with one volume pot, the pickups really should be going to the clockwise lug, and the center lug should be the output, going to the jack (or to the preamp's input in this case). it'll work the other way, but it'll work better this way.
     
  18. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    Why is it better the way you stated? Not arguing, I do want to know why. I was just following EMG's diagram.
    The diagram I was looking at was for one volume knob, 1 pickup, which is what I want (my 2 single coils in series). All I was saying was it was unclear to me, the way they have it the picture looks like a wire terminating to the pot case then another to the lug. I get what you're saying though, and certainly if anyone else is dense like me they'll benefit from this thread!
     
  19. mrufino1

    mrufino1 Supporting Member

    Aug 2, 2005
    Nutley, NJ
    I reversed the pot wiring as suggested by Walter, still want to know what that does though.
    However, I still am having a problem- the volume pot is very noisy when turned and the signal cuts out, comes back on, out then, on when turning it from off to up, opposite when on to off. I was searching on here and it seems like some other people had the same kind of issue. Pot should be good, it's a CTS that is a month old, and it was good passive, so obviously I still have a little work to do. Is this a grounding thing? I have the cavity lined with copper foil, and bridge is grounded. There seems to be a debate on the bridge ground as to whehter it is needed our not.
    Any ideas on what might be causing this? Did I forget a ground wire somewhere? Strange, but I am looking forward to really understand this.
     
  20. lug

    lug

    Feb 11, 2005
    League City, Tx

    Even though the pot is new, there is still an 87.2% chance it's the problem from you description of the symptoms.
     

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