Steve Harris SPB-4 Hum

[Dirtbagger]

Hello. I installed the pickups in my 2011 Fender American P bass. Install went well but when I rest my thumb on pickup cover I get a static hum. The stock pups were dead quiet. The pickups come from the factory copper shielded. The cavity is lined with conductive paint and I checked all connections with the multi meter and am getting a 12.87 reading. The ground wire under bridge is fine as well as the ground inside the cavity. The pickups sound fantastic but was curious about the hum. Thanks.

 

[ThreeChordWonder]

Check the pickup impedances are within range, then double check all your solder joints. Humming is usually caused by a bad ground. Did you remember to re-install the bridge ground?

 

[Clint 55]

The only thing I can think of is you can check to see if the ground wire is soldered to the bridge or not. Sometimes they come installed not. It helps to solder the bridge ground to the bridge.

 

[ThreeChordWonder]

^ If you can't solder to be bridge itself, eg because it's chromed, you can either scrape off some of the chrome where it won't be seen or put a loop of wire under the bridge and around a mounting screw. Tightening down the screw will usually mean you get metal to metal contact.

 

[Dirtbagger]

Thanks for the help. I appreciate it.
The pickup impedance is within range. I checked all solder joints and they are fine. The only wires that I disconnected/soldered are the hot and ground.
I purchased the bass new (2011) and never unscrewed the bridge to check the ground until now. The bridge and ground are making good contact.
I did some reading on the Talkbass site and usually if a hum is happening when touching pickups/pole pieces but stops when touching the bridge, strings or tuners it is a shielding issue, so I might look into shielding the cavities with copper tape. I’m not sure why I have to do this with these pickups though.
I don’t always rest my thumb on the pickup cover and as long as I don’t do that, it is fine.
I also noticed that the hum is most noticeable when the tone is all the way on. I don’t usually play with the tone on full so I have ways to work around it.
Because the stock pups were quiet and never had this issue, I was curious as to why this might be happening.
I did come across temporary fixes: coating the pole pieces with clear nail polish, putting electrical tape across the top of pups and using solid pup covers.
The pickups sound great and are quite an improvement over the stock pups.

@Clint55 I see you are in Santa Fe, I’m in Albuquerque.

 

[Clint 55]

Cool