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Help troubleshooting Jazz bass
- Thread starter skycruiser
- Start date
Oddly? Seems like you're acting as a devil's advocate, dude...
Just let it go, try to pretend I'm not here.
When you turn the pot all the way up it connects the wiper to the terminal. Moving the pickup lead to the output jack is electrically identical to turning up the volume to max. So this seems like an unnecessary thing to check, or maybe you could explain what this might reveal.
To check if the pickup is the cause of the noise. Eliminate that from the equation. Then you can concentrate on the rest of components. That's what I do and that's what I'm suggesting you to do
Ok but I don't understand how moving a wire to an electrically equivalent position can tell you anything. It's like measuring a voltage at the other end of a wire.
You are suspecting that it is the pickup. To eliminate doubt, hook the pickup directly on the output jack and see if it causes the same noise. Hot and ground straight to the jack.
While the whole thing is worth watching in 1.5 speed, please also skip to 10:40 of this video. There are better ways to ground, but I feel that If you solder grounding wires more like that guy, you'll definitely scorch less, or even zero pots.
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Exactly. To solder that quickly you need a high power iron, so you get in and out fast without spending a lot of time heating up the entire pot case.
An even better test would be to disconnect the pickups completely and wire 50K resistors in place of where the pickups connect to the controls, and see how much hum is observed.
I found another clue today but not sure where to go from here.
I swapped out the pickups and found the same problem - higher noise on the bridge pickup that doesn't cancel with the neck pickup. After trying to isolate the noise various ways (even connected each pickup directly to the output jack with everything else disconnected), nothing affects the difference in noise. Looking at the 2 bodies, one other major difference is the metal pickguard on the new bass. I took the pickguard off and found that the neck pickup starting making a similar higher freq and volume noise. They sound similar, but still do not fully cancel when turned all the way on. The bridge noise still overpowers the neck pickup. Nothing I can do with shielding reduces the bridge pickup noise to match the neck pickup. I even covered the entire bass in grounded aluminum foil and the noise still comes through. So as I said, I have no idea where to go from here. Seems like nothing can be done to kill the noise. And it seems to be specific to the body, not the pickups (the other J bass was dead silent with both pickups on).
I have another problem that I mentioned in another post. I'm not sure if I overheated the pot terminals or what, but I have a lot of intermittent issues with the pickup signals. I'll solder one on, test it, have a normal output signal. Then go work on the other one. Come back and the first one isn't working. If I push on the input wire near the terminal it will cut in and out. Maybe this are just particularly crappy pots or something. I may swap the pots over from the other bass.
I have spent a LOT of time with this and feel like I haven't gotten anywhere at all. It's just a simple passive J bass! Shouldn't be so difficult to make it sound "normal", right???
I swapped out the pickups and found the same problem - higher noise on the bridge pickup that doesn't cancel with the neck pickup. After trying to isolate the noise various ways (even connected each pickup directly to the output jack with everything else disconnected), nothing affects the difference in noise. Looking at the 2 bodies, one other major difference is the metal pickguard on the new bass. I took the pickguard off and found that the neck pickup starting making a similar higher freq and volume noise. They sound similar, but still do not fully cancel when turned all the way on. The bridge noise still overpowers the neck pickup. Nothing I can do with shielding reduces the bridge pickup noise to match the neck pickup. I even covered the entire bass in grounded aluminum foil and the noise still comes through. So as I said, I have no idea where to go from here. Seems like nothing can be done to kill the noise. And it seems to be specific to the body, not the pickups (the other J bass was dead silent with both pickups on).
I have another problem that I mentioned in another post. I'm not sure if I overheated the pot terminals or what, but I have a lot of intermittent issues with the pickup signals. I'll solder one on, test it, have a normal output signal. Then go work on the other one. Come back and the first one isn't working. If I push on the input wire near the terminal it will cut in and out. Maybe this are just particularly crappy pots or something. I may swap the pots over from the other bass.
I have spent a LOT of time with this and feel like I haven't gotten anywhere at all. It's just a simple passive J bass! Shouldn't be so difficult to make it sound "normal", right???
I described that back in post #48. Reversing the pickup did not change the noise. But I did confirm they are RWRP - with one reversed and both fully on, the sound was very thin.
I'm thinking that you have a set of mis-matched pickups. They should both have close to the same DC resistance and inductance to properly null out common mode noise.
I swapped in a completely different set of pickups that were silent in the other bass when turned up all the way. In this bass they have the same noise as the ones I removed. Seems to be an issue with the bass, not the pickup sets. I also confirmed that when the other electronics are completely disconnected, the individual pickups connected directly to the output jack have the noise. Seems to be a weird issue with pickups installed in this bass. Very frustrating!
To me this sounds like:
You aren't 100% sure or confident with your soldering technique when soldering the pre-tinned wire onto the terminal. And with fully hardened, maximum contact. Are you not using enough heat, or you are soldering wires to terminals without waiting 4 seconds for them to fully harden?
Also what solder, iron and tip are you using?
*If you put pressure on a solder joint and its intermittent, then it needs to be resoldered correctly.
keep findng that intermettence though because it is a clue showing you what to reflow the solder on. It's not a further problem unless the part is faulty or corroded internally.
So yeah pressing or joints for intermittence is a good way to see if they need the solder reflowed or possibly more added. And you don't need much.
I sometimes use a chopstick as a push tester for intermittent connections.
Thanks for the advice. I'm using a fairly high-end soldering iron, Hakko 939. I actually have quite a lot of experience soldering, wiring and building electronics, having done professional electrical engineering work for over 2 decades as well as going through professional solder and inspection training more than once. That may why I am so annoyed with the whole idea of soldering to the back of a potentiometer. It is not something I would ever include in an electrical design. I think it is a horrible way to do a ground electrical connection, and is only done because at the point of first assembly, can be done without any major issues. Try reworking a few times or applying heat repeatedly and you will see that the entire pot can get very hot, and this is just getting it up to the point that the solder will melt. No matter how you slice it, you have to dump a sh!tload of heat into the metal casing to properly melt solder to it and make a solid connection.
What I believe is going on with the pots is that I spent too much time on the leads with the iron wicking off excess solder. I like to clean up a terminal before putting the wire back on. And now I have done this repeatedly with these pots, going back and forth with various tests. Most likely the heat damaged the metallic element (maybe a small PCB trace or copper foil) connecting the terminal to the inner parts of the pot. It works when hot but cools and shrinks, disconnecting the contact. Just speculation but I can assure you, from inspection, the wires are soldered well to the terminals. I have looked at thousands of solder joints in the last couple of decades and know what cold solder joints, disturbed joints and a wide range of other defects look like. I'm not having issues connecting wires to terminals.
Having said all that - this does not address my real problem at all, that being the noise that was present in this bass before I ever touched it with a soldering iron, and that has not changed substantially since I very carefully shielded everything and carefully checked all of the shielding to have <1ohm to ground. I suspect that is has something to do with shielding - the bridge-position pickup is noisy when connected to either pot or when directly connected to the output jack. I swapped in a completely different set of pickups and it has the exact same problem. These were silent when both fully on in a similar bass.
What is baffling me is there is nothing substantially different between these 2 basses (except of the aluminum pickguard). BUT even with the pickguard off, the noise does not cancel well. Not like the other bass that sounds as noiseless as a P-bass when both of the pickups are at full. This bass is nowhere close to that with 2 different sets of pickups.
I appreciate all the help and have tried my best to try all of the suggestions. Unfortunately at this point it doesn't seem like I have found the root of the problem. I still have a J bass that doesn't go dead quiet with both pickups on. And at this stage it is bad enough to be unplayable for recording. It just won't work with this much noise. So I need to find the problem and fix it, or do something drastic. I'm eyeballing the dumpster at the apartment complex down the street at the moment...
Your bass hummed before you shielded it - and exhibits the directional characteristics we expect. That means it's not cancelling electromagnetic fields - the RWRP situation that should exist between the 2 pickups doesn't.
You shielded it. Shielding helps with electrostatic fields (they're not the same thing). No amount of copper or paint shielding will ever help with electromagnetic fields - you need hum cancelling pickups to do that, and ...we established earlier on that you don't have hum cancelling pickups. So, your bass reacts the same to electromagnetic hum fields - that is to be expected.
Either one of your pickups is reverse wired, or the pair you have is not RWRP with respect to one another. Shielding is not your problem - the way your pickups are wired is. Whether the pickups are at fault, or the wiring in the bass is at fault is yet to be determined.
You shielded it. Shielding helps with electrostatic fields (they're not the same thing). No amount of copper or paint shielding will ever help with electromagnetic fields - you need hum cancelling pickups to do that, and ...we established earlier on that you don't have hum cancelling pickups. So, your bass reacts the same to electromagnetic hum fields - that is to be expected.
Either one of your pickups is reverse wired, or the pair you have is not RWRP with respect to one another. Shielding is not your problem - the way your pickups are wired is. Whether the pickups are at fault, or the wiring in the bass is at fault is yet to be determined.
