Jazz bridge pickup noise

[EJWW]

Hi BC'ers 🙂

 

I've recently taken possession of an early 2000s Japanese 62 reissue Jazz.

 

It sounds great but after many years away from single coil pickups I'm finding the bridge pickup a problem. 

 

The neck pickup is silent but the back one hums like hell and touching the strings or bridge actually causes MORE buzz.

 

The control cavity only has the metal plate along the base, as does the pickup cavities. 

 

Is a lack of decent shielding the issue here? Both pickup outputs are fine and sound good. 

 

I have recorded a video to show what's happening. 

 

Any advice for next steps greatly appreciated 👍

 

 

 

 

Edited December 22, 2024 by EJWW

[tauzero]

Have you delved into it yet? Could it be something as simple as the bridge pickup being connected reversed? I'd take off the control plate and scratchplate and see if the pickups were both connected the same way round, and also check that they're physically installed the same way round (having a wild thought that one might have been reversed on installation and then connected the wrong way round so it was in phase).

[EJWW]

  On 23/12/2024 at 02:34, tauzero said:

Have you delved into it yet? Could it be something as simple as the bridge pickup being connected reversed? I'd take off the control plate and scratchplate and see if the pickups were both connected the same way round, and also check that they're physically installed the same way round (having a wild thought that one might have been reversed on installation and then connected the wrong way round so it was in phase).

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Thanks for your reply @tauzero

 

Here are a few pics under the bonnet. I've no idea what I'm looking at. All looks tidy enough to my untrained eye but.... what do you think?

[Hellzero]

Looks like the bridge itself is not grounded anymore.

 

That's the small copper flat "wire" coming from under the bridge and going in the bridge pickup cavity where it should soldered to the grounding plate.

[EJWW]

  On 23/12/2024 at 10:46, Hellzero said:

Looks like the bridge itself is not grounded anymore.

 

That's the small copper flat "wire" coming from under the bridge and going in the bridge pickup cavity where it should soldered to the grounding plate.

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That's just the angle of the pic I think. 

Here is another, I think the strip and plate are connected ok. 

[itu]

Could you please take one more picture of the jack? Does it have the ground wire soldered, or is your bass relying on screws only?

[EJWW]

  On 23/12/2024 at 15:09, itu said:

Could you please take one more picture of the jack? Does it have the ground wire soldered, or is your bass relying on screws only?

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Not sure... here is a pic

[itu]

OK, the ground is connected to output jack only by relying on screws. Wouldn't be my choice.

 

You see the not connected eyelet: there should be a wire to the closest pot for reliability.

[Hellzero]

I would even recommend to ground all the 3 pots casings by soldering a wire going from one pot to the next one then to the next one and to the free eyelet on the output jack, so the grounding will be way better and not relying on the screws connectivity only.

[EJWW]

  On 23/12/2024 at 21:11, itu said:

OK, the ground is connected to output jack only by relying on screws. Wouldn't be my choice.

 

You see the not connected eyelet: there should be a wire to the closest pot for reliability.

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  On 24/12/2024 at 08:25, Hellzero said:

I would even recommend to ground all the 3 pots casings by soldering a wire going from one pot to the next one then to the next one and to the free eyelet on the output jack, so the grounding will be way better and not relying on the screws connectivity only.

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Thanks guys, so in summary the wiring is not sufficiently grounded so if I solder some wire as above that should resolve the hum issues?

[tauzero]

  On 25/12/2024 at 00:14, EJWW said:

 

Thanks guys, so in summary the wiring is not sufficiently grounded so if I solder some wire as above that should resolve the hum issues?

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It may... Might also be worth unscrewing the bridge and making sure that that end of the tape is making good contact with it.

[Hellzero]

  On 25/12/2024 at 00:14, EJWW said:

 

Thanks guys, so in summary the wiring is not sufficiently grounded so if I solder some wire as above that should resolve the hum issues?

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As @tauzero added, put all the chances on your side. 😉

 

That said, only a full shielding with cavities star grounded really resolves these issues...

[EJWW]

  On 25/12/2024 at 03:08, tauzero said:

 

It may... Might also be worth unscrewing the bridge and making sure that that end of the tape is making good contact with it.

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  On 25/12/2024 at 10:16, Hellzero said:

As @tauzero added, put all the chances on your side. 😉

 

That said, only a full shielding with cavities star grounded really resolves these issues...

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Right, so that is my project over the Xmas hols. 

Thanks for the tips guys. 👍

[Count Bassy]

  On 25/12/2024 at 10:16, Hellzero said:

As @tauzero added, put all the chances on your side. 😉

 

That said, only a full shielding with cavities star grounded really resolves these issues...

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 In industrial installations the star grounding idea has largely been replaced by "grid" style grounding, where you essentially ground every thing you can, everywhere you can.

It is far more effective for high frequency noise, such as that from PCs, dimmer switches, inverters, motor drives etc. Certainly any screened cables should have the screen earthed at both ends! Screening still needs to be close to 100% though.

 

If your problem is only mains hum then conventional "Earth the Screen at one end only" screening can work. Actually at low frequencies you may get away with a single screened plate, such as the aluminium foil sometimes found on the back of the scratch plate. If it is earthed then an electromagnetic wave is reflected with a phase change, so, at low frequncies, the incoming wave and the reflected wave pretty well cancel out.  Full screening is still better though.

 

[Hellzero]

Indeed @Count Bassy, but then we enter the antenna domain...

[Count Bassy]

  On 26/12/2024 at 11:22, Hellzero said:

Indeed @Count Bassy, but then we enter the antenna domain...

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Exactly. It's something we never used to have to worry about. These days we need to!