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Help troubleshooting Jazz bass

#101
You never did state if you had a reductuon in hum by reversing the phase on one of the pickups. Never mind how it impacts the bass tone; that's a separate issue. You have to do exactly what is asked and report back in clear terms of what the result is for any meaningful troubleshooting to take place, without going around in circles.
 
#102
byacey said:
You never did state if you had a reductuon in hum by reversing the phase on one of the pickups. Never mind how it impacts the bass tone; that's a separate issue. You have to do exactly what is asked and report back in clear terms of what the result is for any meaningful troubleshooting to take place, without going around in circles.
Click to expand...
Yes I did, post #48. Reversing the bridge pickup did not change the noise of each pickup solo.
 
#105
skycruiser said:
Electrically this is no different than simply turning the pots all the way up. That connects the wiper to the upper output terminal, i.e. the output node of the circuit. I have tested that the post are working correctly.
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Sure, that's the theory :). Theoretically you have no hum, but obviously we're not there yet. When nothing makes sense, I find it helpful to test all of my assumptions and eliminate as many variables as possible. So far you know there's something about this bass that's causing a problem, and this would help narrow down what that something is. Worst case scenario, you find out that you're right and there's nothing wrong with the pots.
 
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#107
skycruiser said:
Electrically this is no different than simply turning the pots all the way up. That connects the wiper to the upper output terminal, i.e. the output node of the circuit. I have tested that the post are working correctly.
Click to expand...
Yes, but you are overlooking the parallel resistance to ground through the pot. Have you measured with an ohm meter and verified the pots are equal in value?
 
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#109
What I am convinced is happening is that I have two pickups that respond in an imbalanced way to EM noise sources present in my music room. The reason is related to shielding. I have shown that the noise in the pickups is orientation dependent (presumably related to the direction of the EM signals in the room) and that it is substantially suppressed when shielded with the aluminum plate. This is true for both pickups, as shown in the two videos. I believe the reason I am having trouble with this bass is because it has an aluminum pickguard, something I didn't have with my previous Jazz basses. This PG is providing substantial shielding for the neck pickup (this is basic EM attenuation which is dependent on the thickness of the metal), leaving the bridge pickup open to interference. With my previous basses, both were noisy, which is a point that I made from the start - that the neck pickup is unusually quiet for a J bass in my room. And where I am now with this bass, it is almost like a PJ bass, the neck pickup being nearly silent. I have not had this with my other J basses, and I credit the aluminum guard for this.

I don't believe there is anything else wrong with the electronics or anything wrong with the pickups either for that matter. Nothing I found in the hours investigating the issue indicated anything wrong with the electronics, well - except for parts I damaged myself. I swapped pickups and they had the same problem. I have tested the pots and they are normal. I've done tests to show the pickups are RWRP and they check out. I even replaced one pot with one from another working bass and it had no impact on the noise. (I would have replaced both but the shaft was the wrong size). I shielding the living poopie out of the cavities and around the wiring and this had no impact.

I may experiment with adding a thicker guard to the bridge pickup just to prove to myself that my conclusions are correct. It will be too ugly to keep as a permanent part.

Thanks again for all the help. I don't plan on doing any more experimenting with the circuits at this point.
 
#110
Aluminum is a poor shield for electromagnetic radiation; you need ferrous metal for that- Mu metal.

So if I understand you correctly, you don't believe there is any problem with the pickups in this instrument now, yet you have another bass with the same jazz setup that is hum free, compared to this instrument?
 
#111
byacey said:
Aluminum is a poor shield for electromagnetic radiation; you need ferrous metal for that- Mu metal.

So if I understand you correctly, you don't believe there is any problem with the pickups in this instrument now, yet you have another bass with the same jazz setup that is hum free, compared to this instrument?
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Sorry but the statement about aluminum is 100% incorrect. Any good conductor (such as aluminum and copper, both non-ferrous) will attenuate radiant energy (EM waves). Please, let's not spread incorrect information.

As for your second statement, no you do not understand correctly. The other bass is only hum free when the pickups are both set to fully on (or to any balanced setting). They each exhibit hum/noise when the levels are not balanced, just like any Jazz bass will.
 
#112
skycruiser said:
Sorry but the statement about aluminum is 100% incorrect. Any good conductor (such as aluminum and copper, both non-ferrous) will attenuate radiant energy (EM waves). Please, let's not spread incorrect information.

As for your second statement, no you do not understand correctly. The other bass is only hum free when the pickups are both set to fully on (or to any balanced setting). They each exhibit hum/noise when the levels are not balanced, just like any Jazz bass will.
Click to expand...
Non ferrous conductors are sufficient for electrostatic noise, but not very good for electromagnetic fields. This is why low level audio transformers are often shielded with mu metal. Mu-metal - Wikipedia
Electromagnetic shielding - Wikipedia scroll down to Magnetic Shielding, under 100Khz...

So, this contentious instrument is actually hum free with both pickups volume controls wide open?
 
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#113
byacey said:
Non ferrous conductors are sufficient for electrostatic noise, but not very good for electromagnetic fields. This is why low level audio transformers are often shielded with mu metal. Mu-metal - Wikipedia

So, this contentious instrument is actually hum free with both pickups volume controls wide open?
Click to expand...
Mu metal is for magnetic shielding. Again, 100% incorrect about conductors and EM fields. Go study Maxwell's equations.

I don't know what instrument you are asking about. Do you have a point you are working around to?
 
#114
Can't read the whole thread.
Have you tried Removong the pickguard and see if the neck pickup is as noisy as the bridge pickup?
Have you tried a plastic pickguard?
Have you tried swapping bridge pickups with the other bass?
 

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