New Yamaha BB34P grounding issue?

wellsyboy

So I have been enjoying my new Yamaha 4 string bass but noticed something off today which I managed to trace to the bass side of the spilt 'P' pickup. I was noticing some serious buzzing and first thought I was a bit too close to the computer monitors in my den (as the PUPs are single coil). However it only happens when my thumb touches the pole piece under the low E string. When I realised this I touched the other poles on that split - same thing. Nothing on the other split (the ones under the D and G strings) and nothing on the bridge pickup. Makes me think this is a faulty pickup and not just a ground wire issue. I will, of course, be phoning the Yamaha store on Monday but any thoughts or suggestions from any techs on her would be most welcome. Thank you in advance.

ICBM

Yes, faulty pickup - the insulation on the coil wire is broken where it wraps around the polepiece and is making an electrical contact so you’re effectively touching the hot wire.

You could get around it by reversing the hot and ground connections on both pickups (so they remain in phase) which will make the polepiece grounded instead of hot, but if the bass is new that’s not really your problem.

wellsyboy

ICBM said:

Yes, faulty pickup - the insulation on the coil wire is broken where it wraps around the polepiece and is making an electrical contact so you’re effectively touching the hot wire.

You could get around it by reversing the hot and ground connections on both pickups (so they remain in phase) which will make the polepiece grounded instead of hot, but if the bass is new that’s not really your problem.

Thank you - weirdly it wasn't doing it last night so I'm sitting here scratching my head.

ICBM

wellsyboy said:

Thank you - weirdly it wasn't doing it last night so I'm sitting here scratching my head.

That type of fault can be intermittent. The wire is only just touching the polepiece, so it could be temperature-dependent.

The problem is that if you send it back and it’s not doing it at the time they test it, they’ll think it isn’t faulty. Best to take a video showing the problem, if you can get it to do it again!

wellsyboy

Thank you - good idea!

wellsyboy

An update - buzzing disappeared as soon as I changed back to unwrapped strings - took it in to Yamaha anyway - no issues found - the only time you can hear any hum/buzz is when you touch the bass side split pole pieces with an amp turned right up AND ONLY if you are not touching any strings at the same time. AND it seems that all their passive basses with that pickup do it - took several off the wall in the stop to test it out. playing normally with an amp cranked no issues whatsoever unless using nylons wrapped strings.