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Help troubleshooting Jazz bass

#42
I'm an accredited CET, and have been working on professional broadcast and recording equipment for the past 39 years. If you want believe a bad pot can generate hum in a passive bass, go for it. The only way I can see that happening is an open ground connection, which is not the same as a damaged pot.

By the way, soldering to the case of a pot is not done as a "cheap fix". Doing so ensures a low impedance star ground buss point that also includes the pot case, bushing and shaft as part of the ground shield. This is better than relying on the control nut and bushing being tightened against an aluminum or copper foil for grounding the pot.
 
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#43
Alessandro Cruz said:
Just an example:

6898175825_2df10be58a_b-jpg.1910386
Click to expand...
Those are soldered to the back of the pot. Now you have extra hardware and wires for no reason at all.

Also, your cavity isn't shielded. That plate at the bottom, that you stabbed triangles into your body, then soldered the plate to, isn't doing anything.

Again, extra hardware, extra damage, for no reason at all.
 
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#44
byacey said:
I'm an accredited CET, and have been working on professional broadcast and recording equipment for the past 39 years. If you want believe a bad pot can generate hum in a passive bass, go for it. The only way I can see that happening is an open ground connection, which is not the same as a damaged pot.

By the way, soldering to the case of a pot is not done as a "cheap fix". Doing so ensures a low impedance star ground buss point that also includes the pot case, bushing and shaft as part of the ground shield. This is better than relying on the control nut and bushing being tightened against an aluminum or copper foil for grounding the pot.
Click to expand...
In his defense, that's a metal control plate. If one pot is connected to ground, the control plate it's attached to is, and also every pot that's bolted to it. It wouldn't work on anything else. Only the one pot is actually in the ground loop. If the plate weren't metal, he'd get no sound.
 
#45
skycruiser said:
Does not appear to be the pots. Noise from the bridge pickup is the same with either pot. I tried disconnecting each pickup one at a time, then switched pots, one at a time and then both swapped. The noise follows the bridge pickup.

I also shielded the bridge pickup wires through the hole between the pu cavity and the electronics cavity. No impact on noise.

Measured pickup resistance.
Bridge 7.34k
Neck 6.98k

Maybe it's time for a pickup swap...
Click to expand...
Pull your pickup off, heat up the leads on the bottom of them, and swap the wires.
 
#46
I'm having problems. I've tried reversing one pickup and now I'm getting intermittent signals on both. They.cut in and out. If I slightly move the wires the signals cuts on and off. Either I damaged the pots while soldering, or I have a wire broken that is connecting on and off as it moves, or there's a tiny shorting thread of wire somewhere. I tried putting them back in the original positions and both are cutting out. It is getting very frustrating. I may need to fully disassemble and see if the pots are ok.
 
#48
I backed up and resoldered. Still getting intermittent signal on the bridge pickup but long enough to test the polarity swap.

When I reversed the bridge pickup, with both pickups fully on I got a very thin sound. I think this confirms they are reverse wound. And I confirmed the magnets were opposite polarity. So all evidence points to these being a properly matched RWRP pair.

Resistance was posted above, around 7k each.

Also, the bridge pickup was still noisier than the neck pickup when reversed. No noticeable difference. And the noise does not go away when both are turned up all the way.

I seem to be back to a pickup problem. The noise is not balanced between them so they don't cancel. Though I have to say that neck pickup is the most quiet single coil pickup I've had in a J bass.
 
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#49
JeezyMcNuggles said:
Those are soldered to the back of the pot. Now you have extra hardware and wires for no reason at all.

Also, your cavity isn't shielded. That plate at the bottom, that you stabbed triangles into your body, then soldered the plate to, isn't doing anything.

Again, extra hardware, extra damage, for no reason at all.
Click to expand...

It's not my photo, not my bass, and definitely not my job. I was trying to show the lug inside the cavity.

As you may have noticed, it's a bass with two stacked pots. Perhaps not the best picture to use as an example...

And that's why I posted the link right after that....
 
#50
byacey said:
I'm an accredited CET, and have been working on professional broadcast and recording equipment for the past 39 years. If you want believe a bad pot can generate hum in a passive bass, go for it. The only way I can see that happening is an open ground connection, which is not the same as a damaged pot.

By the way, soldering to the case of a pot is not done as a "cheap fix". Doing so ensures a low impedance star ground buss point that also includes the pot case, bushing and shaft as part of the ground shield. This is better than relying on the control nut and bushing being tightened against an aluminum or copper foil for grounding the pot.
Click to expand...

Oh nice, but I prefer to take the opinions of the bass makers, preamp makers, pickups makers. Sorry...
 
#53
skycruiser said:
I backed up and resoldered. Still getting intermittent signal on the bridge pickup but long enough to test the polarity swap.

When I reversed the bridge pickup, with both pickups fully on I got a very thin sound. I think this confirms they are reverse wound. And I confirmed the magnets were opposite polarity. So all evidence points to these being a properly matched RWRP pair.

Resistance was posted above, around 7k each.

Also, the bridge pickup was still noisier than the neck pickup when reversed. No noticeable difference. And the noise does not go away when both are turned up all the way.

I seem to be back to a pickup problem. The noise is not balanced between them so they don't cancel. Though I have to say that neck pickup is the most quiet single coil pickup I've had in a J bass.
Click to expand...
New pickups.
 
#54
Alessandro Cruz said:
It's not my photo, not my bass, and definitely not my job. I was trying to show the lug inside the cavity.

As you may have noticed, it's a bass with two stacked pots. Perhaps not the best picture to use as an example...

And that's why I posted the link right after that....
Click to expand...
That would only work in a bass with a metal plate, or excess sheilding though. The reason you solder it to the pots, is to ensure a solid ground connection to all metal parts. It has nothing to do with speed. It actually takes longer to tag each one separately,and then run it to the sheilding. But, it's definite.
 
#56
skycruiser said:
I seem to be back to a pickup problem. The noise is not balanced between them so they don't cancel. Though I have to say that neck pickup is the most quiet single coil pickup I've had in a J bass.
Click to expand...

I would agree it's a pickup problem. It's easy for the poles to couple with the coil and introduce noise. Likely that's what's happening here. If you love the tone, you could swap in the same pickup from another bass and end up with a quiet pickup. Unless you get unlucky again. You didn't mention which Squier Jazz you have, but I've handled plenty with dead silent pickups (and a few that behaved like yours).
 
#58
dwizum said:
I would agree it's a pickup problem. It's easy for the poles to couple with the coil and introduce noise. Likely that's what's happening here. If you love the tone, you could swap in the same pickup from another bass and end up with a quiet pickup. Unless you get unlucky again. You didn't mention which Squier Jazz you have, but I've handled plenty with dead silent pickups (and a few that behaved like yours).
Click to expand...
It is a 40th Anniversary Vintage Jazz.
This is my second one. The first had the exact same problem. I exchanged it for this one and decided to keep it and try to fix it. Maybe that was a mistake. It seems unlikely to pick up 2 basses with the same defect though.
 
#60
I would love to see manufacturers add solder tabs to the back of the pot - something like this:
upload_2022-12-24_10-39-1.png


A couple of tabs that give you direct contact to the case without the thermal sink headache that goes along with directly soldering to the back chassis plate. You would think these could be features added to the stamped out and bent sheet-metal used to make the casing. Maybe just make these for the commonly used guitar market: 250k, 500k audio taper pots.

What I like about terminals is that you can easily clean up the solder using braid wick. That's a little harder to do on the back of the pot. Takes a lot of heat, and in my experience the solder just flows out and ends up covering the entire pot. Maybe this is more of a problem when doing rework and repair, and not an issue in the original assembly process. If that's the case, there's no driver to make a change like this.
 

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