Blend pot problem

Discussion in 'Hardware, Setup & Repair [BG]' started by basss, Jan 14, 2002.

  1. basss

    basss Supporting Member

    Aug 27, 2001
    I just put a blend pot on my bass. The bass has two passive pickups and is wired vol-blend-tone. It works BUT when the blend is at the center detent the volume is cut and gradually increases as I pan towards either pickup. Did I buy the wrong pot? Does anyone know of a blend pot that works with passive pups without affecting the volume? Thanks
  2. elwood

    elwood there is no spoo

    Jul 25, 2001
    Mid-Hudson Valley, NY
    1. What is the value of the pot? Generally, 500K for humbuckers, 250K for other.

    2. Have you got the pot hooked up correctly? It's easy to miswire one of these. If you know how to read resistance and can use an ohmmeter, check your connections. My money is on an incorrect hookup.
    Also, were you replacing an existing blend pot or changing from a VVT setup?


  3. basss

    basss Supporting Member

    Aug 27, 2001
    Its a 500K pot that is replacing a vvt setup with humbuckers. Im pretty sure I have it wired correctly. I had a wiring diagram that I was following. It works correctly- it pans from one pickup to the other its just that the volume drops as I pan towards the center detent. Could an incorrect hookup be the cause of this? Im thinking that the pot is designed to equalize the combined volume of two blended pickpups to that of one single pickup but is overcompensating. If its not the wiring I guess I need to replace the pot. Do you have any sources for blend pots that work with passive systems?
  4. notduane


    Nov 24, 2000
    Here's somethin' from Stew-Mac -- click
  5. basss

    basss Supporting Member

    Aug 27, 2001
    This is actually the diagram I followed and I got the pot from them too. Has anyone else used this 500K blend pot and had similar problems? Maybe its my pickups or the pot is bad or my wiring... although I think I hooked it up right:confused:
    Thanks for your help!
  6. Ok, is Source A and B connected properly?

    Are the wire links in place and not shorting anything out?

    Ermm what value of tone capacitor have you got across the tone control?

    Make sure there is no solder bridging between anything.

    Make sure all grounds are ok. Its not the pot, because its working on either side.

    Have you got all the links on the Volume Pot correct? Is the lump of solder on top of the pot good?


  7. basss

    basss Supporting Member

    Aug 27, 2001
    Im using a .1mf capacitor- the tone control seems to work fine. I was pretty careful with my soldering so I dont think its that.
    I guess I did change a couple things from the diagram. I didn't solder anything to the back of the pots. I just went from ground lug to ground lug. What is the purpose of soldering ground wires to the back of the pots?
    Also I have a ground wire connected to the ground lug on the tone pot- I have a feeling this could be the problem. In the diagram there would be an extra wire from the ground lug on the volume pot to the right most lug on the tone pot.
    Does the tone pot need to be grounded?
    What is the purpose of that wire that is soldered to the side of the tone pot in the diagram? How could it ground anything if its not connected to any other wires? Or can a pot be grounded by soldering a ground wire to the side of the pot? Thanks and sorry for all the newbie questions.
  8. Carey


    Jan 18, 2002
    Redlands, CA
    Could be your pickups are out of phase. Also, there is a right and a wrong way to wire a blend pot. Make sure the ground side and the hot side are not reversed. Stew Mac blend pots are not the best in the world. They tend to have an uneven blend. Bartolini ones usually work better, but may not be as available. Grounding the pots to their lugs is simply a way to decrease noise. Generally it is a good idea to ground all the pots(some folks recommend not grounding the blend pot) to the ground lugs and the ground connection on the jack. This, combined with good shielding,will usually yield the least amount of noise. Good luck!
  9. Ok, here's a suggestion. ALWAYS follow the diagram exactly first time around. That way you can trouble shoot it and get it to work like it is supposed too. Once it is all up and running like they say, then make your own modifactions. It makes it very hard if u start out changing things because you don't know if it works in the first place.

    And yes it is correct about the noise. ;)


  10. I'm going to guess that the pickups are slightly out of phase with each other.
  11. basss

    basss Supporting Member

    Aug 27, 2001
    OK it works now. I replaced the blend pot. The new one I have is wired opposite from what is in the stewmac diagram. I also soldered ground wires to the pots and removed the ground wire from the tone pot's ground lug. Its much quieter and sounds great! Thanks everyone for your responses- I was about to throw in the towel and go back to vol-vol-tone but you guys inspired me to keep on playing with it and now it works.:)