Earth hum when touching pole pieces?

Building, Modding, Setup and Repair
Post Reply
bassmaniac69
Posts: 1208
Joined: 16 May 2010, 20:23
Location: Brisbane

Earth hum when touching pole pieces?

Post by bassmaniac69 » 24 Sep 2017, 21:21

So my new Yamaha BB735A has been humming like nothing else, I thought it was home but it also did it on the gig last night, it drove the drummer crazy...

I've discovered that it hums when I touch the pole pieces of the P bass (it's a PJ config) and not the J bass pickup.

All wires in the control cavity etc. look fine and connected, so is it a bad earth grounding or such? It does it in either active or passive mode.

The bass is under warranty and I've contacted Yamaha I'm just wondering if it's something I could fix myself rather than having to get it to a repair agent etc...

User avatar
aphekgreg
Posts: 2328
Joined: 24 Nov 2009, 16:10
Location: Narara Central Coast
Contact:

Re: Earth hum when touching pole pieces?

Post by aphekgreg » 24 Sep 2017, 23:05

Most basses need to be better insulated from RF noise. I'm amazed at how little effort most manufacturers put into shielding the cavities and pickups. With pickups, I stick a piece of copper tape to the polepieces and connect that to ground. It usually makes a significant difference. I'll use the same tape to shield all the cavities, making sure they're all connected to ground.
Greg

Ibanez Musician, MusicMan, Dingwall Z3, Rickenbacker, MIJ Fender Precision & Jazz, Warmoth/Musikraft P/J-bass, Danelectro Longhorn.
Traynor YBA300, MarkBass, GK1001RB2, Berg AE212, Hartke 4.5, '64 Fender Bassman
http://www.aphekstudio.com.au

User avatar
Petebass
Posts: 8532
Joined: 31 Oct 2008, 07:07
Location: Hervey Bay, QLD

Re: Earth hum when touching pole pieces?

Post by Petebass » 25 Sep 2017, 05:53

aphekgreg wrote:
24 Sep 2017, 23:05
With pickups, I stick a piece of copper tape to the polepieces and connect that to ground. It usually makes a significant difference. I'll use the same tape to shield all the cavities, making sure they're all connected to ground.
This!

I had the same problem when I reassembled my modified Stingray 5 after refinishing it. Grounding the pole pieces solved the problem of them making noise when touched. Shielding the cavity made the bass silent.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

User avatar
noplanb
Posts: 1317
Joined: 04 Dec 2012, 22:00
Location: Adelaide

Re: Earth hum when touching pole pieces?

Post by noplanb » 25 Sep 2017, 08:56

+1 to the aboves. I was astounded how quiet my JB4 with tapewounds was, once I'd foiled/grounded all the cavities
I see..............basses!

User avatar
DoctorJohn
Posts: 253
Joined: 30 May 2016, 13:10
Location: SA

Re: Earth hum when touching pole pieces?

Post by DoctorJohn » 25 Sep 2017, 09:35

+1 to copper shielding. I did the cavity of my jazz bass with that snail guard stuff from Bunnings. Worked a treat

Also, depending how bad your ground hum is, you can use a gate to silence hum during quiet periods of a set.

bassmaniac69
Posts: 1208
Joined: 16 May 2010, 20:23
Location: Brisbane

Re: Earth hum when touching pole pieces?

Post by bassmaniac69 » 25 Sep 2017, 12:13

Thanks for the hints all. The shielding is not that bad inside but could always do with some improvement.

Can any one supply pics/links of how they grounded the pole pieces, I'm assuming it's all internal I'm just having trouble visualising it!

I won't do anything until Yamaha get back to me and have a go at resolving the issue. For the moment I have put some gaffa tape over the closest pole piece and it's stopping any contact hum for now but I will do more permanent fixes for sure.

jimmyjam
Posts: 301
Joined: 18 Oct 2009, 10:26
Location: "Fat Cat City" AKA Canberra

Re: Earth hum when touching pole pieces?

Post by jimmyjam » 25 Sep 2017, 12:17

Sell the Yamaha and buy a new TBX. Oh and one for me too!
"I play bass, most kinds!"

User avatar
Petebass
Posts: 8532
Joined: 31 Oct 2008, 07:07
Location: Hervey Bay, QLD

Re: Earth hum when touching pole pieces?

Post by Petebass » 25 Sep 2017, 17:57

bassmaniac69 wrote:
25 Sep 2017, 12:13

Can any one supply pics/links of how they grounded the pole pieces, I'm assuming it's all internal I'm just having trouble visualising it!
Somewhere to start:-

http://www.audereengineering.com/FAQ_PUMag_Gnd.htm
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

User avatar
aphekgreg
Posts: 2328
Joined: 24 Nov 2009, 16:10
Location: Narara Central Coast
Contact:

Re: Earth hum when touching pole pieces?

Post by aphekgreg » 25 Sep 2017, 18:30

Here's some I made and are just out of the potting wax here. No different to shielding other pickups. With the P pickup, you need to connect the two halves, otherwise only one side is shielded. The copper shielding needs to be connected to ground or it won't do anything. I'm using wire with two cores and a shield here. You'll need to run an extra wire to ground on your pickups.

Image
Greg

Ibanez Musician, MusicMan, Dingwall Z3, Rickenbacker, MIJ Fender Precision & Jazz, Warmoth/Musikraft P/J-bass, Danelectro Longhorn.
Traynor YBA300, MarkBass, GK1001RB2, Berg AE212, Hartke 4.5, '64 Fender Bassman
http://www.aphekstudio.com.au

User avatar
bassbass
Posts: 791
Joined: 14 Nov 2008, 16:05
Location: Melbourne
Contact:

Re: Earth hum when touching pole pieces?

Post by bassbass » 17 Nov 2017, 09:45

With respect to the other guys here, copper tape is a poor way to earth alnico magnets. Believe me, this won't last. Even if the copper tape has conductive adhesive, I've found that the connection breaks down over time. (I'm not sure why. I've seen many pickups with this problem over the years. I've also tried in on my own basses. Yet I see it as a solution on TB etc all the time.) The best way to permanently earth polepieces is with conductive paint. Use a strip of copper tape say, down one side, and have the paint overlap the tape and the pole pieces. Then you can solder your earth to the tape.
I've discovered that it hums when I touch the pole pieces of the P bass (it's a PJ config) and not the J bass pickup.
Do you have elixers or tape wounds? Does the hum diminish when you touch the pole pieces and the bridge at the same time? Humming pole pieces usually are much less of a problem if you are also touching the strings, but coated strings are insulated from the bridge earth.

Do both sides of the P pickup hum? If one side hums but the other is silent, then the bass is wired correctly, and the simplest solution is simply to remove the pickup and reinstall it with the e-a and d-g bobbins reversed. My thumb touches the pickup when I play my P bass, so I have the noisy coil under the d-g strings where I will never brush it with my fingers.

If both sides of the P pickup hum, you should notice that one side hums louder than the other. Ideally, you should reverse the phase of the P pickup, and have the quiet coil under the e-a strings, (especially if you use coated strings). But this means also reversing the phase of the J pickup, and you've mentioned that this doesn't hum when touched, so that may be not ideal. I'd certainly check the continuity of the J pickup pole pieces with earth using a multimeter. If they are earthed, then reversing its phase won't matter.
robkiddmusic.com
fb/robkiddmusicofficial

Post Reply

Who is online

Users browsing this forum: No registered users and 3 guests