Series II loud noise from neck PU

[el8ed]

Hello all,
My Series II short scale is acting up. While practicing today suddenly there was an increasing random loud noise on the neck pickup. I’ll attach a short audio file — caution! It is very loud.


I tried with a different power supply, even unplugged the pickup momentarily, changed filter settings, rotated the PU volume and master volume with no effect. The noise was random and intermittent, but it always came back.


The neck pickup plays cleanly and noise free.


I’ll also include a photo of the electronics cavity.


Any suggestions would be greatly appreciated.
Cheers, Oliver

[adriaan]

Sounds like a cell phone at close range. Switch it off, or keep it away from the bass.

[el8ed]

Thank you Adriaan, but the closest cell phone was about 15 ft away, where it always is when I am practicing. This happened after about an hour of playing with no apparent reason. I did practice a few Stanley Clarke riffs, so I might have been banging on the bass a bit ...

[mica]

We're thinking the filter opamp might be sick. You can swap the bass and treble pickup filter ICs and see if the problem switches channels.

• Bass Filter
• Treble Filter
• Bass pickup preamp
• Hum X preamp
• Treble preamp

Let me know what you find out.

[JimmyJ]

Oliver,

Sorry to hear about your trouble.  Definitely not cell phone interference which in my experience is a more "organized" kind of noise...  Yours sounds more like something on your preamp card.  I would open the preamp panel and gently tap around on the card to see if you can find a component which responds by sending noise down the line.  (Keep that amp volume low - yikes!).

Even the best electronic parts can fail but I've only ever lost one preamp board component in all my years of playing.  That was one of the FETs which are the small "cans" nearest the pickup connectors.  That's the very first amp in the chain so if one of those goes haywire the noise gets amplified twice further making it quite a racket.

As Mica said, the 5534 opamps are in sockets and can be swapped around if you suspect one of those.  Be careful not to bend the pins and to keep the chips oriented correctly.

If it's a FET you may need to send it in for repair.  Has your bass had the low-noise upgrade?

Hope it gets sorted out!

Jimmy J

[el8ed]

Thank you Mica! I will certainly try this … if the problem comes back.


Adriaan's suggestion got me curious and so I went back and played the bass for another hour … no noise, just glorious SII bliss.

I’ll keep an eye (or ear) on it and try the OP swap if it comes back.

@JimmyJ - I don’t think my bass has the upgrade, but it has always been very quiet. I’ll be extra careful with the chips, thanks — had some experience with that in the 80’s ...


Thanks to all of you for the quick help.
Cheers, Oliver