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P-Bass Tone pot Works As Volume/Tone Blend? NBD gone sideways.

Discussion in 'Pickups & Electronics [BG]' started by GravyGoodness, May 14, 2020.


  1. OK I need some pro help here.

    Brand new Bass - MIM 50's Precision - got in the mail yesterday - factory sealed. Turns volume knob to 10 - barely any sound at all. Turns Tone knob up and there's a volume sweep (maybe 20% of "normal" output) but it blends in tone as well as you sweep up.

    Looked at wiring diagrams last night, checked ground which is solid for sure and based on 2 different diagrams I changed location of ground from Tone pot to Ground side of jack and ground side of volume. No difference in result.

    I'm good at wiring and great at soldering, but complete garbage at diagnosis. Any thoughts from the pros on here?? I can rewire the whole thing, but I'd rather replace/repair what's really wrong instead of throwing $50 at the problem and totally ripping the guts out and redoing the whole thing. Plus I get to learn something about troubleshooting this way. I can answer any other questions you might have for me in an effort to get this righted. Save my NBD please!

    BIG THANKS just for looking! I appreciate the insight.
     

    Attached Files:

    alanloomis1980 likes this.
  2. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    It may just be the angle of the photo, but where is the tone cap?
    Anyway, if this if factory new, have the manufacturer sort it out. No new bass should be accepted when defective.
     
  3. Clark Dark

    Clark Dark

    Mar 3, 2005
    earth
    If memory serves me correctly on a P-Bass there are two wires, black and white. The white wire goes to center lug on volume pot and the black goes to ground. In your pic it seems the white wire from pickup is going to left lug which isn't right. If this is an out of the box brand new bass I'd send it back if not comfortable checking it. If you are comfortable then change connections.
     
  4. JTE

    JTE Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    Hot (white) goes to one outer lug of the volume pot. That lug has a jumper over to the tone control's wiper (center) lug. The wiper on the volume control goes to the hot of the output jack. So the volume control should work correctly. All the way to one side the wiper is directly connected to the PUP hot and sending that signal to the output. At the other extreme of the volume pot the wiper is shorted to ground, shorting the output to ground also. The signal path to the tone control send the signal to the wiper so at one extreme there's 250K ohm resistance between the signal and the cap so it doesn't bleed much treble to ground. At the other extreme the signal is shorted to ground through the cap. That appears to be what you have (assuming the capacitor is hiding under the black wire in the photo, on the left side of the tone pot.

    I'd do this first- unsolder both pickup wires from the pots and use some alligator clips to plug the PUP leads directly into an amp. Make sure both coils of the PUP are working correctly. If so, hook 'em up again and make sure the solder joins are sound mechanically and electrically. Reflow the solder on all the joints and retest. But that's because I used to manage a store and I'm good with rewiring and troubleshooting, and that assumes that I like the bass (not the model, but this specific chunk of wood and metal). If those don't apply to you and because it's a brand-new reputedly factory sealed box, I'd be calling the retailer who took my money and getting it replaced with a correctly functioning bass.

    But then I don't see the point in getting a factory-sealed bass unless I'm paying the factory directly. Why didn't the retailer open the box, inspect the goods, and make sure everything was right?
     
  5. It's a 2 year old bass that Fender has discontinued - and after months of looking is the very last Brand New one I could find. Cheaper than the used ones now might I add. Makes sense that I found this thing in a weird corner of the internet. A Camera Store in NYC that sells pro audio stuff as well had this. But was listed as brand new, and they have a no hassle return policy. Buuuut, this is the Bass I want and there's only so much to go bad, I wouldn't hassle with a return since everything else is pure perfection on it. Plus there is nothing to replace it with.

    I'm bothered at how it's stumping me though.
     
  6. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    If the two legs of the capacitor are touching, or if the leg that's soldered to the pot lug is touching the body of the pot, there's your problem. It seems to me this would be the most likely point of failure.
     
    GravyGoodness likes this.
  7. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    It appears the cap is edgewise under the bridge ground wire in the picture.
     
  8. JKos

    JKos Supporting Member

    Oct 26, 2010
    Torrance, CA
    As @Killed_by_Death said, check where the capacitor is soldered to the potentiometer lug. Is it touching the pickguard?

    Another quick test would be to disconnect the wire between where the pickup hot comes in and the tone pot. Does the volume now work properly?

    - John
     
    GravyGoodness likes this.
  9. Guys, I appreciate the feedback, you don't even know.

    I took it to the guitar shop today to have them check with a multimeter and maybe offer advice. He didn't have time at the moment so I reluctantly left it during lunch.

    I got back at 530, he had scratched the front of the finish dragging the pickguard off without pulling the strings, all the wiring was removed and THERE WAS A BURN from the soldering iron on the black by where a side Jack would be. Bruh. I was not a happy boy. Just to clarify I wanted to know what was wrong. Not fix it.

    At the end of the day I made $200 and have 2 new pots and a cap to install. I will MAKE SURE I install it as mentioned in this thread. Will report back soon.

    Pic attached, this is how I got it back.
     

    Attached Files:

    robert43 and Killed_by_Death like this.
  10. 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.

     
    Feb 27, 2021

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