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Tone pot not changing tone

Discussion in 'Pickups & Electronics [BG]' started by Bassndrums73, Feb 22, 2021.


  1. Bassndrums73

    Bassndrums73

    Mar 13, 2018
    Ohio
    This may be a bit long so bear with me. I have a Fender Jazz Lightweight Ash Edition bass. I don’t like the sound of the Vmod pickups that come stock in it. Because of this and because I love the sound of the Ultra Noiseless pickups that came stock in my Fender Ultra Jazz Bass I bought a set of Ultra Noiseless pickups to put in this Lightweight Jazz. The Ultra Jazz has a switch so you can run it either passive or active but the Lightweight Ash Jazz is a passive only bass. When I installed the Ultra Noiseless pickups in the Lightweight bass the neck and bridge pickups both work when you turn each individual knob up, but the tone knob does not change the tone at all. I even bought new harness from a vendor with an upgraded capacitor and it does the exact same thing. No tone knob change. Could this have something to do with the Ultra Noiseless pickups not being strictly passive pickups? Everything is wired exactly to the wiring diagram. Thanks for any help you can suggest.
     
  2. mcontour

    mcontour Supporting Member

    Apr 27, 2008
    Loveland, Colorado
    Photo of the electronics please?
     
    LoveThatBass likes this.
  3. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    Did the tone knob work prior to you changing the pickups? To be honest it sounds like you installed the new harness incorrectly. Make sure the tone circuit is grounded. Meter it from the volume out tab to the tone in tab, and from the ground side of the capacitor to the jack sleeve; you should read 0 ohms in each case. Now meter from the tone in tab to the tone out tab. You should get variable results as you turn the knob anything from 0~(value of your pot.) Next meter the cap itself by metering from the tone out tab to the ground side of the cap. You should read some resistance (more than 0 ohms but less than open.) Finally make sure the third tab on you tone pot isn't connected to anything. If everything checks out, your cap value is too low.
     
    Last edited: Feb 23, 2021
    Zooberwerx likes this.
  4. dwizum

    dwizum Supporting Member

    Dec 21, 2018
    I will second what @sissy kathy suggested. The tone control is either not grounded, or not connected to signal.
     
  5. Bassndrums73

    Bassndrums73

    Mar 13, 2018
    Ohio
    Thanks for the replies. I will have to wait until I get home from work to work on it again. I will report back later.
     
  6. 1958Bassman

    1958Bassman

    Oct 20, 2007
    Make sure a wire isn't touching the two tabs on the pot that aren't soldered to the case- that bypasses the pot. The pot could be shorted internally, too. If you have a multi-meter, you can check this.
     
  7. Bassndrums73

    Bassndrums73

    Mar 13, 2018
    Ohio
    401EDE11-C718-4D93-B367-60ED1358C715.jpeg 9944371A-4FB5-4DA2-9053-773D45AB1D56.jpeg A11C16CA-46FD-47A6-BD0A-2214DF493EC6.jpeg F33FF4F6-F7EB-4F86-956B-7B0A527FD527.jpeg Here are some pics. The 3 ground wires soldered on the bottom of the neck volume pot are from the neck pickup, the body ground and the bridge ground. The white positive lead from the neck pickup is on the center pot terminal. The bridge pot has the positive red wire from the bridge pickup to the center terminal on the pot. The pickup black ground wire is soldered to the bottom of the pot. The rest of the wiring is the way it came presoldered from the vendor I bought it from. I can’t see any wires or solder touching anything it isn’t supposed to. I will have to go buy an ohm meter to check values and for any shorts. That will be a new experience for me so don’t be surprised if I come back and ask more questions. The cap says .047 +/-10 400 volt. My vender said it is an upgraded cap. Here are some pics.
     
  8. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    Well tha cap certainly isn't too small. I think I see a black wire running from the left vol tab to the left tone tab. If both the tone pot and cap are good, I'm out of ideas.
     
  9. Bassndrums73

    Bassndrums73

    Mar 13, 2018
    Ohio
    Well I purchased a high quality Fluke meter today. I did each and every point to point test sissy cathy gave me to try. Every one tested at the values you gave with one exception. The capacitor itself shows no value at all when the in and out sides of it are touched with the probes. The reason I bought a new pre-assembled harness and control assembly is because I was having this exact problem with the tone pot not changing the tone on the old one. It appears both capacitors on these are bad because when I checked the capacitor on the old harness assembly it doesn’t show anything either. Is it possible both are bad or could I be doing something wrong? Keep in mind I have never done this before but everything else checked out exactly as sissy Cathy said it would.
     
  10. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    As you know I gave a vey wide range for the capaciter to be okay. If your reading falls outside those parameters, you have a bad cap. Yes it's possible to have two bad caps.
     
  11. Bassndrums73

    Bassndrums73

    Mar 13, 2018
    Ohio
    There was no range present at all. The meter was as if I wasn’t touching with the probes on each side of the cap at all. Guess I should replace with another cap and see if it fixes the problem.
     
  12. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    I retired 20 years ago so am no longer familar with fluke meters Refer to the manual and see if you have multiple ranges that can be selected for reading resistance. Just before I retired Fluke came out with a meter that automatically selected the resistance range, but that meter was close to $1,000.
     
  13. JeezyMcNuggles

    JeezyMcNuggles

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    It's wired wrong. You've got the hot being controlled by the tone pot. You don't need a hot on the tone knob. Hook the right node to the pot, capacitor to center node with one side touching the ground. Run your hot from your input plug, straight up to your pickup volume.
     
  14. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    How do you propose getting the signal to the tone without running a hot to it?
     
  15. mcontour

    mcontour Supporting Member

    Apr 27, 2008
    Loveland, Colorado
    Hello Jezzy.

    I'm not sure I follow what you are saying. To me, it appears that the bass follows the standard Jazz Bass wiring diagram below.

    If I had the bass in my hands, I would check out that tone pot by measuring the the resistance across the two wired connections with the tone control set to full and to off. Full should give the value of the pot. Off should be zero.

    From the amount of solder on the back of the pot, I suspect that the pot was overheated and potentially damaged....

    -Michael

    jb.jpg
     
    dwizum likes this.
  16. dwizum

    dwizum Supporting Member

    Dec 21, 2018
    I'm not quite sure if I'm following your description, but his wiring appears to match standard Jazz Bass wiring as far as I can tell:

    [​IMG]

    Capacitors can be tricky to measure with some multimeters. Here's Fluke's instructions:

    How to Measure Capacitance with a Digital Multimeter.
     
  17. JeezyMcNuggles

    JeezyMcNuggles

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    My bad guys. I do wire the hot in there. But, I just do it differently. Haha, I went and checked it out. Scratch that last one. But, I do always run my capacitors to the center. Just like a Pickup. The pot could be bad.
     
    Last edited: Feb 23, 2021
  18. dwizum

    dwizum Supporting Member

    Dec 21, 2018
    I agree with that approach.

    Just to reiterate what I mentioned above, checking a cap with a multimeter can be confusing. Setting most meters to resistance mode will cause them to pass a small current through whatever you're testing, and you'll just end up charging the cap very quickly - at which point it'll show an open circuit. You might see a resistance reading flash up on the screen for a second, but then it'll go away. So I'm not really convinced that your caps are bad, based on the test you tried to do.

    Many multimeters have an actual capacitance testing function, check if yours does. My cheapo $50 meter does.
     
  19. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    OP has already established that the pot is good. He put a resistance probe across the two tone tabs and got a variable reading when turning the knob.
     
  20. You can't measure that capacitor in circuit. One leg of the cap would have to be unsoldered before measuring.
    The easiest way to verify if the tone control is good is this: Short the leads of the capacitor together with a clip lead jumper, plug the bass into an amp and see if the tone control can vary the volume between full on and silent.
     
    JeezyMcNuggles likes this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 7, 2021

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