Tone pot not changing tone

Photo of the electronics please?

 

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

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.

 

How do you propose getting the signal to the tone without running a hot to it?

 

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

 

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:



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

How to Measure Capacitance with a Digital Multimeter.

 

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.

 

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.

 

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.

 

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.